Volume 60, Nelson, 1998
view papers Overview
Feed not weeds – doing the basics well
PETER BROOKER
Margaret and I own and operate a farm of 260 effective ha in the Maruia Valley. We have a 230-cow dairy unit on 125 ha and use the remaining area to support the dairy operation and run 450 ewes and approximately 60 beef bulls. During the late 1970s and early 1980s we developed a large area of manuka and fern country into pasture. As we were working reasonably large areas of difficult country, some areas were quite rough when sown down and the home block was abandoned in terms of cultivation for a number of years. Since 1985 we have undertaken quite a lot of regrassing of the newer areas and when the decision was made in March 1995 to return to dairying, the home block (now dairy) received some urgent attention and approximately 40 ha of the dairy unit has now been redeveloped. On the dry stock unit we are now growing brassicas to winter the dairy stock. The need to cultivate and regrass or grow a winter crop is determined by three factors: • Pasture production/species of existing pasture. • Contour, infestation of rushes, cutty grass, drain spoil, etc. • Compaction and therefore pugging problems. Over the last 10 years we have sown a variety of species, with the main emphasis on short- to medium-term ryegrasses mixed with clovers and timothy. We have had very good results with these varieties, especially when considering the excellent autumn/early spring production of these species and the importance of fully feeding early in the season to capture milk, beef and lamb growth opportunities. The lack of stem weevil, good fertility and moisture levels ensures many good seasons out of short-rotation species. Low endophyte levels in pasture are also a benefit. When a paddock is earmarked for regrassing, a soil test is done if fertility is questionable. Most of our farm has adequate base phosphorus and pH levels. The dairy unit levels range between 30 and 40 P, and 5.8 pH. The dry stock areas range from 25+ P, and 5.6–5.8 pH. All other major elements are in the optimum range. Annual fertiliser (N/P/K/S) application is: Dairy 114/50/80/87 Dry stock 30/25/25/35
New Zealand's grasslands 1958–1998: retrospective foresight
JOHN LANCASHIRE
The only reason a large part of the New Zealand pastoral sector has remained in business in the last 20 years is because of the high rate of capital gain on farmland. Much of this increase is owing to non-farming factors such as population increases, lifestyle blocks and more lucrative uses for land such as forestry. The lack of profitability is owing to the fact that the industry is still largely in the 'commodity' trap which comprises 80% of exports. A massive change of direction to added value niche products is required if the inevitable decline of the industry to third world status is to be arrested. However, there are some very promising signs within the country that the wine industry model can be developed in the food industry. Regional characteristics and a New Zealand style "terroir" are emerging with a number of very successful small food businesses setting new standards and a new philosophy. International trends in the food industry suggest a superb window of opportunity for New Zealand in the area of high value clean green nutritional foods. This challenge must be accepted if the pastoral sector is to survive as a viable force in the New Zealand economy. Keywords: commodities, food, regions, terroir, nutrition
Pasture growth on dairy farms in the Golden Bay and West Coast of the South Island
K.L. DAVIS, N.A. THOMSON, N.R. MCLEAN, D.A. MCCALLUM, R.J. HAINSWORTH, A.J. WARDS and R.G. BARTON
Pasture growth was monitored on 22 farms covering Golden Bay, Nelson, Murchison and West Coast districts during 1994 to 1997. Pasture growth was measured monthly from grazed pasture using the rising plate meter (RPM) and the difference method. Pasture growth from the South Island sites were compared with growth at the WestpacTrust Agricultural Research Station (WTARS) in South Taranaki, measured by the more traditional trim method, and the difference method as used in the South Island study. The pasture growth recorded was then used by the dairy farm production model UDDER to predict the planned start of calving (PSC), stocking rate and milksolids (MS) production at maximum net financial return for seven districts. At WTARS the average pasture production recorded by the difference method was 16.3 t DM/ ha and by the trim method, 12.9 t DM/ha, the greatest difference between the two methods occurring in late spring/early summer. Pasture production on the south Island sites varied from 9.6 (Taramakau) to 16.1 (Grey Valley) t DM/ha. The major factor identified as influencing pasture growth, in an environment where rainfall for 91% of the sites exceeded 2000 mm, was number of frosts. A multiple regression combining pasture production climatic and soil nutrient variables identified number of frosts and Olsen P as the major factors influencing pasture production (R2 = 0.25). The use of the growth from seven districts by UDDER showed a marked variation in management practices and MS output. PSC varied from the first 10 days in August (Takaka, Nelson, Westport) to the last 10 days in August (Murchison). Stocking rates ranged from 2.0 cows/ha at Motueka to 3.3 cows/ha on an irrigated farm in the Nelson district. MS production/ cow differed little among districts and MS production/ha reflected stocking rate, ranging from 650 kg/ha for Motueka to 1150 kg/ha for Nelson. The main factor driving stocking rate and PSC was winter pasture production. Keywords: climate, dairy production modelling, pasture production, soil fertility
view papers Dairy Farm Systems
Chicory for milk production
C.D. WAUGH, D.A.CLARK, S.L. HARRIS, E.R. THOM, P.J.A. COPEMAN and A.R. NAPPER
The 1997–98 season has seen a marked increase in the amount of chicory planted on dairy farms in New Zealand. However, no New Zealand data are available for milk production from dairy cows grazing chicory. As part of a larger trial examining the effect of summer forage crops on milk production, Grasslands Puna chicory was compared with Barkant turnips. In January and March 1998, grazing trials were conducted at No.1 Dairy, Dairying Research Corporation using 60 lactating twin cows. In January, chicory and turnips were break-fed at a constant allowance (4 kg DM/cow/ day) to supplement pasture offered at 3 allowances (15, 27.5 and 40 kg DM/cow/day). In March, these crops were fed at 3 levels (0, 4 and 8 kg DM/cow/ day) to supplement pasture offered at a constant allowance of 25 kg DM/cow/day. Chicory and turnips gave similar milksolids (MS) responses of 40–41 g MS/kg DM offered in January. Milksolids responses in March were higher for turnips, 34 g MS/kg DM vs 32 g MS/kg DM from chicory. In January and March the size of the milksolids response declined with increasing allowance. This could be attributed to an increasing amount of substitution at higher allowances. Chicory produced between 8.8 and 13.8 t DM/ha from 4 October to 10 March, offering a high quality summer-autumn forage crop and improved milk production when supplemented with pasture. Keywords: chicory, Cichorium intybus, pasture allowance, dairy cows, milk production, forage crops, turnips, milksolids
More Summer Milk – a further investigation into improving summer milk production
H.P. SIMONS, N.A.THOMSON, D.F. MCGRATH, and J.E. DAWSON
An on-farm demonstration designed to increase summer/autumn milksolids (MS) production was continued during the 1997/98 dairying season. The study investigated the combination of an earlysummer application of nitrogen (N) fertiliser and a 40-day grazing rotation (the treatment), compared with each trial farm's normal farming practice (the control). The study began on 1 November 1997 with the equal split of herds and farms into farmlets. On the treatment farmlets, 60 kg N fertiliser/ha was applied in November. All treatment herds were on a 40-day rotation from 15 December until drying off. The average rotation for the control herds was 25 days, varying between 18 and 30 days. The season was warmer and drier than average, with four of the five farms experiencing a drought from January to early March. The treatment grew an additional 3.3 tonnes DM/ha to the beginning of June, 49% of the response occurring within the first 42 days of applying N fertiliser. The extra pasture grown on the treatment farmlet had little effect on daily MS production, and overall there was a net loss of $86/ha to the treatment. Possible reasons for this lack of response include overestimation of pasture growth, poor pasture utilisation, and low protein levels. Despite the additional pasture available in mid lactation, the advantage to MS production occurred only at the end of the season, allowing the treatment cows to milk for 8 extra days. Keywords: milksolids production, pasture production, grazing management, rotation length
Pasture species and drought impact on milk yield 1. Milk yield responses in the Waikato
E.R. THOM, D.A. CLARK, V.T. VAN VUGHT and C.D. WAUGH
Milksolids (MS) production of Jersey cows grazing different pasture species mixtures over summer and autumn is described for the first two years of a 4-year trial. Four pasture mixtures were established after cultivation in autumn 1996, and were compared with existing ryegrass–white clover pastures. The mixtures were: (1) high-endophyte perennial ryegrass–white clover (2) tall fescue, phalaris, cocksfoot, white clover, red clover (3) same as (2) plus paspalum (4) endophyte-free ryegrass, timothy, white clover, red clover and (5) existing high-endophyte ryegrass, white clover. Milk tests were in January-February of 1997 and 1998. Cows were offered a single pasture allowance. Cows on high-endophyte ryegrass mixtures consistently produced low MS yields compared with those on tall fescue mixtures and endophyte-free ryegrass. In 1998, responses for cows grazing ryegrass–white clover (5 and 1) were significantly less than from tall fescue-based pastures (2 and 3) (0.74 vs. 0.86 kg/cow/day), and responses from cows on ryegrass/timothy based pastures (4), were better than for all others (0.96 kg/cow/day). Important determinants of the MS responses were the high rust infection and low contents of white clover in the high-endophyte ryegrass (1) pastures, and the high contents of red clover in the tall fescue and endophyte-free ryegrass-based pastures. Keywords: cocksfoot, cow grazing, irrigation, milk production, pasture quality, perennial ryegrass, phalaris, red clover, tall fescue, timothy, triple mix, white clover
Pasture species and drought impacts on milk yield 2. Predicted farm milk yield at four sites
D.J. BARKER, D.A. CLARK, E.R. THOM, J.N. COUCHMAN, R.N. BURTON and N. DYMOCK
A desirable option for increasing milk yield per farm is to increase milk production in summer without compromising peak-season production or the duration of lactation. The dairy industry has a goal to achieve a 4% per month post-peak decline of milk production. The effect of five pasture types and two summer water regimes on predicted farm milk yield, in Northland, Waikato, Manawatu and Canterbury was measured over 1 year. Two pasture treatments, resident pasture and Grasslands Nui ryegrass, were common to all sites. A third pasture treatment varied between sites: triple mix (Grasslands Advance tall fescue, Grasslands Kara cocksfoot, and Grasslands Maru phalaris) at the Manawatu site; the same triple mix but with Grasslands Raki paspalum at the Northland site; and low-endophyte ryegrass and Grasslands Kahu timothy (LER) at the Canterbury site; all sown treatments included red and white clover. All five pasture types were included at the Waikato site. On average for all pasture types, water deficit reduced summer herbage accumulation (HA) to 79, 68, 43 and 18% of irrigated controls, and annual HA to 88, 80, 73 and 63% of irrigated controls in Northland, Waikato, Manawatu and Canterbury, respectively. Since farm milk yield predicted by UDDER was highly correlated with annual HA (R2 = 83%), the effects of pasture type and water deficit on milk yield were similar to effects on HA. Seasonal and annual HA differed among the five pasture types at each of the four sites. The most important factor affecting predicted farm milk yield was annual HA, with relatively little effect from the seasonal pattern of pasture growth. Differences in shapes of the predicted milk supply curves for various treatments occurred, particularly when drought forced early drying-off. The best predicted summer milk yield was for the Canterbury irrigated LER pasture treatment, a 6.8% per month postpeak decline of milk production. Keywords: farm milk yield, farm system modelling, forage supply, pasture species, water deficit
The impact of feeding maize silage on dairy production
N.L Thomson, K.L. Davis, J.M/McGrath, R.J. Hainsworth, J.C. Clough
A farm system study was run on the Waimate West Demonstration Farm in south Taranaki during the 1996/97 and 1997/98 dairying seasons. The aim was to investigate the effect of time of feeding purchased maize silage on milksolids production.
view papers Nutrient Sustainability
Long-term effects of grazing on the fertility of soils
R.A. CARRAN and P.W. THEOBALD
The long-term effect of excreta return was studied on a bull-beef system that had been under stable management for 23 years. Excreta return did not greatly affect organic matter properties. Mineralisable nitrogen showed differences with depth where excreta had or had not been returned, but was not different in the 0–75 mm soil depth. Excreta return positively affected Olsen P, sulphate-sulphur and organic-sulphur soil test values. Single-core sampling studies showed that very high Olsen-P values occur in some cores and can weight the paddock mean upward, resulting in the phosphorus status being overestimated for much of the area. Excreta return strongly influenced potassium cycling, by maintaining a large pool of available potassium. A relatively small amount was lost to drainage water, however, as the cycling potassium displaced calcium and magnesium. Magnesium loss from the system was large compared with the quantity cycling, and appears to be one of the major long-term negative effects of grazing on nutrient reserves. Keywords: excreta return, grazing, soil fertility, soil nutrient reserves
Long-term fertiliser application and fertility of hill soils
M.G. LAMBERT, A.D. MACKAY and D.A. COSTALL
Application of phosphatic fertiliser to legume/grass pastures, and increased stocking rate, is commonly assumed to increase soil organic matter (estimated from soil carbon) content, to lower soil pH, and to increase soil Olsen P status. Changes in these variables in soils derived from sedimentary parent material were monitored over 16 years, in a longterm grazing experiment on southern North Island hill country. There were 2 fertiliser treatments, principally high (capital applications followed by 375 kg/ha/year) and low (125 kg/ha/year) superphosphate application. There was a net loss of soil C of approximately 200 kg/ha/year in both treatments, although annual C inputs to the soil were greater (by 1000 kg/ha) in the high fertiliser soils. Soil pH increased slightly; and Olsen P status reflected P application, although it was less responsive to P application (13 kg P/ha applied above maintenance for 1 Olsen P unit increase) than has commonly been assumed is the case (4–7 kg P/ha per unit). The most likely reason for net loss of soil C is increased decomposer activity in the soil, and the greater proportion of plant-fixed C ingested by grazing animals as a result of intensification. The lack of a decline in soil pH may have been related to the declining soil organic matter level lowering hydrogen ion-supplying power. The lower-than-expected responsiveness of Olsen P to fertiliser P application was probably because the experimental area had a very poor fertiliser application history, in comparison with previous experiments against which Olsen P was calibrated. Keywords: carbon, fertiliser application, hill country, Olsen P, organic matter, pH, soils
Sulphur fertiliser and sheep grazing capacity
D. SCOTT
Sheep grazing capacities over 15 years from two long-running high country trials in a moderate rainfall zone and under 30 different annual sulphur and phosphorus fertiliser combinations are presented. With time, the sheep grazing capacities became increasingly related to the rate of S fertiliser input, and largely independent of P fertiliser rate. The implication for grazing capacity, fertiliser purchase, transport and spreading costs is the very large cost benefit that could accrue from further development of methods for handling and spreading elemental S fertiliser. Keywords: fertiliser, grazing, high country, phosphorus, sulphur
The long-term phosphate experiment at Hamilton, Victoria
J.W.D. CAYLEY, G.R. SAUL and M.R. McCASKILL
At Hamilton, Victoria, the effects of grazing pressure and amount of single superphosphate (SSP) applied, on the productivity and soil resource status of grazing systems based on sheep, have been assessed since 1979. Early work showed that marginal and absolute responses in DM production to SSP were greater when assessed by measuring the net growth of grazed pastures compared with mowing, and that largest response occurred in spring. The botanical composition of the pasture has been dramatically influenced by the amount of SSP applied. Ryegrass and subterranean clover now constitute only 2.3% and 11.0% where an average of 1–4 kg P/ha has been applied each year. In addition, the digestibility of herbage from wellfertilised treatments was 4–9 units higher than from low-fertility treatments. The combination of these effects has allowed achievable annual gross margins to increase from $100/ha at low-fertility treatments to about $400/ha with 18 kg P/ha applied annually. Indicators of sustainability show that so far there have been no major environmental consequences of applying SSP in amounts well above that used by district farmers. Keywords: botanical composition, gross margin, pasture quality, phosphorus, sheep, sustainability
Why do pastures respond to lime?
D.M. WHEELER and M.B. O'CONNOR
Lime responses in pasture have been attributed to amelioration of aluminium (Al) and manganese (Mn) toxicity, increased plant availability of nitrogen (N), phosphorus (P) and molybdenum (Mo), and increased soil moisture. Methods of assessing the occurrence of each of these mechanisms are given, illustrated using results from two contrasting lime trials where mechanisms of lime response were determined. The results indicate that lime responses on the Mangatea soil could be attributed to lime increasing N, P, and Mo availability, and to the amelioration of Al toxicity allowing better access to soil moisture over summer. In contrast, on the Matapiro soil lime responses were owing to enhanced N mineralisation. The results show that the occurrence and size of a pasture response owing to a given mechanism are owing to interactions between soil factors, plant species and climate. Hence more complex pasture models than are currently available are required before predictions of the size and duration of lime responses can be improved. Keywords: aluminium, lime, manganese, nitrogen, phosphorus, pasture response
view papers Condensed Tannins
A comparison of the effects of Lotus and white clover on some nutrient cycling factors
J.R. CRUSH and R.G. KEOGH
In a laboratory test, nitrification rates were lower in soil incubated with dried Lotus herbage than in the same soil incubated with white clover herbage. Nitrification rates in soil amended with dried Lotus herbage were higher in soil that had grown Lotus for the previous three years, than in soil that had only one year in Lotus. This was interpreted as evidence for progressive selection for soil microorganisms that can readily decompose Lotus. This conclusion was supported by observation of rapid availability of nitrogen from Lotus herbage and dung when they were added to a hill soil that had grown Lotus for at least 6 years. Field sampling showed higher earthworm numbers under white clover pasture, than under Lotus pasture or ryegrass pasture, which had the lowest number. Dung from animals grazing Lotus pasture was incorporated more rapidly by earthworms than dung from white clover or ryegrass pastures, in laboratory and field experiments. This demonstrated preferences by earthworms among dungs derived from different pasture species. Further work is required to determine the effects on nutrient cycling processes of the different dung incorporation rates that were measured. Keywords: condensed tannins, earthworms, Lotus, nitrogen, nutrient cycling, soil micro-organisms, white clover
Birdsfoot trefoil – an alternative legume for New Zealand dairy pastures
S.L. HARRIS, D.A. CLARK and P.J. LABOYRIE
Two grazing trials conducted with Friesian cows in mid lactation showed milk yields were higher on birdsfoot trefoil (Lotus corniculatus)-dominant pasture (19.8 and 16.7 l/cow/day) than on white clover-dominant (17.8 and 15.4 l/cow/day) or ryegrass-dominant (13.0 and 11.7 l/cow/day) pastures. Increased milk production on the Lotus and clover was attributed to the higher nutritive value of the legume-based pasture compared with the ryegrass, and to higher dry matter intakes. Cows grazing Lotus also had improved feed conversion efficiency compared with those grazing either ryegrass or clover, indicating that the presence of condensed tannins in the Lotus may have contributed to the improved efficiency. Milk protein concentration was consistently higher on the Lotus (3.36 and 3.35%) than on the ryegrass (3.15 and 3.21%) or clover (3.30 and 3.21%) in both experiments, while milk fat levels were lower in Experiment 1. While Lotus increased milk yield and milk protein concentration, its potential as a forage legume for dairy cows also depends on annual herbage production and the determination of how best to utilise it in a farm system. Keywords: birdsfoot trefoil, dairy cows, dry matter intake, Lotus corniculatus, milk composition, milk yield, perennial ryegrass, white clover
Forages with condensed tannins – their management and nutritive value for ruminants
G.C. WAGHORN, G.B. DOUGLAS, J.H. NIEZEN, W.C. McNABB and A.G. FOOTE
Temperate forage legumes that contain condensed tannins (CT) have been evaluated under experimental conditions and some have demonstrated significant benefits for sheep, cattle and deer. Condensed tannins can significantly improve productive performance, as well as lessen our dependence on anthelmintic drenches. However, not all CT are equal and some may not benefit production at all. This paper summarises the performance responses of ruminants to CT in birdsfoot trefoil (Lotus corniculatus), lotus (Lotus pedunculatus), sulla (Hedysarum coronarium), sainfoin (Onobrychis viciifolia) and erect dorycnium (Dorycnium rectum), and indicates the requirements for successful establishment and management of these swards. All require specialist care, and few will compete with common pasture species in high-fertility situations, but the potential benefits of reduced anthelmintic requirements when sheep are fed sulla, and the lowered incidence of flystrike and improved weight gain, wool growth, milk production and ovulation rate attributable to the CT in birdsfoot trefoil, makes these attractive options for farmers. Lotus is a high quality feed for wet, acid, low-fertility soils and sainfoin may result in very good stock performance in dry regions. Annual dry matter yields of the five species outlined here range from about 10 to 25 t/ha and some of these forages will benefit producers who are prepared to manage these forages correctly. Keywords: birdsfoot trefoil, condensed tannin, dorycnium, forage legume, lotus, ruminant nutrition, sainfoin, sulla
The potential benefits of ensiling the forage legume sulla compared with pasture
J.H. NIEZEN, G.C. WAGHORN, T.B. LYONS, and D.C. CORSON
With high dry matter yields of high quality forage, high soluble carbohydrate levels and a suitability for harvest by cutting and removing, the forage legume sulla (Hedysarum coronarium) has the potential to be an important silage crop in New Zealand. In three experiments the ensiling potential of sulla was compared with conventional pasture using a mini-silo system which allows for rapid evaluation of forages using 3–4 kg of herbage. Experiment 1 evaluated the effect of increasing the proportion of sulla in pasture silage (0/100, 25/75, 50/50, 75/25 and 100/0 sulla/pasture). The principal findings were that increasing sulla content of the silage decreased (P<0.001) ammonia content from 5.9% of total N to negligible detectable levels, and increased (P<0.0001) lactic acid content of silage from 3.3% to 9.9% of dry matter (DM) which resulted in a lower final pH (4.9 vs 4.0; P<0.0001). Experiment 2 examined the rate of ensilation of pure sulla and pasture after 1, 4, 8, 11, 13, 15, 28 and 42 days. Silage pH and carbohydrate levels declined more rapidly in sulla than pasture silage, while lactic acid content increased more rapidly. Silage ammonia levels increased rapidly in pasture silage but remained low in sulla silage. In Experiment 3, sulla and pasture mixtures as used in Experiment 1 were ensiled at three moisture levels, in a 5*3 factorial design. Final pH was lower (P<0.001) 17 days after ensiling with increasing moisture content and by increasing the proportion of sulla in the silage (P<0.0001). High moisture silage or silage with a high proportion of sulla, had the highest lactic acid and soluble carbohydrate contents. These studies suggest that sulla has the potential to be used to produce high quality silage. Sulla silage needs to be evaluated in feeding trials to determine if its potential as a high quality supplementary feed can be realised as animal performance. Keywords: ammonia, condensed tannins, Hedysarum coronarium, lactic acid, pasture, pH, silage, sulla
view papers Caucasian Clover
A preliminary cost-benefit analysis for inclusion of caucasian clover in new dairy pasture
G.H. TAYLOR and R.N. WATSON
In a coastal Bay of Plenty trial, ryegrass pasture containing the rhizomatous legume caucasian clover (CC), provided advantages from late spring to autumn in total herbage yield and legume content in the 2nd to 4th years, compared with a ryegrass– white clover pasture. Sub-optimal pasture supply and quality, in summer and autumn especially, can limit seasonal milk production potential. Thus, greater milk yield from pasture which includes CC can be derived from greater dry matter on offer to cows, and also through improved forage quality afforded by increased legume content. CC is slower to establish than white clover (WC) and may be favoured by spring rather than autumn sowing. The extra costs for successfully establishing CC in pasture and the milk yield potential from greater herbage yields and legume content were used to determine the level and rate of economic benefit from its inclusion in dairy pasture. Depending on the assumptions made, CC was calculated to recover net establishment costs in the 4th year, with a net present value over 10 years of $789, or a 35% internal rate of return. At this level of return use of CC in pasture renewal would be an attractive longerterm option. A number of considerations, which need to be taken into account, include as yet unestablished benefits for CC on heavier or moister soils which are less compromising to WC persistence, the slow establishment of CC, the effects of different methods of establishment and longer-term effects of pasture pests on its performance potential. Keywords: caucasian clover, cost-benefit, coastal Bay of Plenty, dairy pasture, Lolium perenne, Trifolium ambiguum, Trifolium repens
Caucasian clover performance in a year of severe drought
R.N. WATSON, F.J. NEVILLE and N.L. BELL
In a year of spring–summer drought on a sandy volcanic ash soil, ryegrass/caucasian clover (RG/ CC) and RG/white clover (RG/WC) pastures had similar rapid increases in pasture growth rates during September. Growth rates peaked around 25 October (65–70 kg DM/ha/day) for RG/CC and around 14 October (50–60 kg DM/ha/day) for RG/ WC. As drought intensified the declines in pasture growth rates were similar, but delayed by up to 3 weeks for RG/CC. Both pastures reached minimum summer growth rates of <10 kg DM/ha/day at the beginning of February (4% soil moisture). Spring/ autumn application of nematicide increased pasture growth. WC was almost completely lost from RG/ WC pasture and was largely replaced by summer grass. Drought did not affect CC plant survival, but some leaf wilting and brown-off occurred in February. Autumn pasture recovery was similar except that the recovery of RG/CC pasture in the absence of nematicide application was delayed and significantly reduced. The absence of clover and replacement by summer grass reduced autumn response to nematicide by RG/WC. On treated RG/ CC plots there was a 96% reduction in root galling by the root knot nematode (Meloidogyne hapla) and reduced populations of grass grub (Costelytra zealandica) and clover root weevil (Sitona lepidus) in autumn. This led to a 107% increase in fine root mass/unit mass of CC rhizome material, compared with untreated CC. These pests depend on, or are favoured by, pasture clover, so that higher populations were retained by the presence of clover in RG/CC compared with the RG/WC pasture. CC can be considered as a drought-persistent rather than a drought-resistant plant. Keywords: caucasian clover, drought, persistence, pests, production, ryegrass, Trifolium ambiguum, Trifolium repens
Sixteen years of caucasian clover under contrasting managements
Hexaploid caucasian clover (Trifolium ambiguum) was one of the components of a 25-species pasture mixture overdrilled into hieracium-infested fescue tussock grassland. The mixture was subjected to 60 different annual sulphur and phosphate fertiliser rate, stocking rate, and stocking method treatments for 16 years. Caucasian clover was slow to establish but increased to become the dominant species in the pastures under high fertiliser inputs after a decade, but only a minor species at lower inputs. Keywords: fertiliser, grazing management, high country, Trifolium ambiguum
Strategies to maximise establishment and production of oversown caucasian clover
W.L. LOWTHER, HEATHER N. PRYOR and K.D. TRAINOR
Caucasian clover (Trifolium ambiguum M. Bieb.) is an alternative legume for areas where white clover (T. repens L.) growth is limited. However, slow establishment has been a problem when caucasian clover has been oversown. Results from two tussock grassland sites have demonstrated the importance of the initial establishment of caucasian clover. Caucasian clover dry matter production after 6 years was still related to original seedling establishment. This result was obtained in ungrazed swards, conditions likely to maximise the ability of caucasian clover to spread by rhizomes and natural reseeding. The results indicate that caucasian clover may make little contribution to legume yield in these environments for at least 6 years unless satisfactory numbers of plants are established initially. Maintenance fertiliser application, in early years at least, appears similar to that required by white clover. Yields of caucasian clover swards in the 6th year when maintenance fertiliser had been applied were 3–7 times those when fertiliser had been applied only at sowing. The paper also provides possible explanations for establishment failures that have already occurred, and provides information on correct management techniques to maximise establishment of oversown caucasian clover. Keywords: caucasian clover, establishment, fertiliser, hill country, inoculation, nodulation, oversowing, pasture, Trifolium ambiguum
view papers Fertilisers
Clover nutrient ratios to monitor pasture yield responses to fertiliser nutrients
J.D. MORTON, L.C. SMITH and J.D. MORRISON
From earlier results of a limited number of trials, ratios of concentrations of phosphorus (P), sulphur (S) and potassium (K) to nitrogen (N) in white clover have been developed as indicators of nutrient adequacy. For 98% of maximum yield, clover herbage ratios of 7.4 (100 × P/N), 5.0 (100 × S/N) and 0.43 (K/N) were required. Mean critical nutrient concentrations have been reported as 0.35% P, 0.28% S and 2.05% K from earlier research on sites at an early stage of pasture development. A series of mowing trials, measuring pasture yield responses to nil or a high rate of P (120 kg/ha), S (100 kg/ha) and K (300 kg/ha) were carried out at 8 sites throughout New Zealand in 1997/98. There were significant (P<0.05) clover or total pasture dry matter (DM) yield responses to P at 7 sites, S at one site, and K at 6 sites. The results indicated that the optimum clover nutrient ratios reported from earlier research are valid over a wide range of environments. Clover P/N and % P, and K/N and % K accurately assessed the effectiveness of P and K applications and were reliable indicators of a pasture yield response. Clover S/N and % S were equally accurate measures of the correction of a S deficiency at the one S-responsive site, but neither measure increased after S application at other nonresponsive sites. Clover S/N was more accurate than % S for indicating a DM response to S. A lower mean critical concentration of 0.24% S in clover would have been more appropriate for these well developed sites. Keywords: nitrogen, nutrient concentrations, nutrient ratios, phosphorus, potassium, sulphur, white clover
Modelling animal treading impacts on infiltration rate
Y. TIAN, P.L. SINGLETON, G.W. SHEATH, D.G. McCALL and W.T. CARLSON
Sediment and chemical losses in surface runoff can be significant on land with rolling topography. These effects can be more severe in grazed pasture systems because of animal treading damage to the ground surface. The phenomenon of treading includes soil compaction, pugging, creating tracks and surface cracking. Modelling results presented in the paper provide estimation of changes in water infiltration rate with land of different topography, soil physical condition, season and grazing. These models were derived from field data collected over 3 years and were specified for micro-sites (0.5 m2). The modelling results identified that micro-site infiltration analysis was appropriate to land with complex grazing and topographic conditions. The correlation between the model estimation and field measures was up to 73% (adjusted R2). Keywords: animal treading, infiltration rate, soil compaction, runoff, cellular automata, spatial modelling
Organic milk production at "Spencerfield"
TOM LAMBIE
In 1982 my family purchased "Spencerfield" which was an 89 ha traditional market-milk dairy farm milking 130 cows on a year-round basis. Since that time we have progressively increased our holding to 308 ha, running 280 cows and 140 head of young stock with all animals grazing on. The cows produce 1.4 million litres of milk or 106 400 kg milksolids, with the emphasis on the production of a minimum 2000 litre per day quota. The stocking rate may seem low; however, we farm in a dryland sheep and cropping district. A water-short catchment means we have only 80 ha of irrigation which is subject to restrictions in an 550 mm average rainfall area. Rainfall ranges between 400 mm and 950 mm.
Pasture responses to phosphorus and nitrogen fertilisers on dry hill country
A.G. GILLINGHAM, M.H. GRAY and D.R. SMITH
In order to evaluate the relative responsiveness of summer-dry hill pasture to phosphate (P) and nitrogen (N) fertilisers, a large scale field trial was established in southern Hawke's Bay in 1995. Pasture growth rates and species, and soil moisture levels were measured on easy and steep slopes of generally north- and south-facing aspects in two pairs of farmlets with either a Low or High soil P status, one of each pair also receiving 30 kg N/ha annually in winter. Soil moisture levels were always higher on south- than on north-facing slopes, the difference being greatest from autumn to spring. However, total annual pasture growth was higher on north aspects because of better winter production, whereas the colder, south aspects produced little pasture at this time. In other seasons, pasture growth was similar on both aspects. Pasture growth was higher on easy than on steep slopes at all times. P responses occurred from spring to autumn especially on south aspects, and on easy north-facing slopes, which showed a large increase in clover growth. N responses were best in winter and autumn especially on steep, north aspects and at Low P conditions. N application depressed clover production, especially in the High P+N fertiliser treatment, where there was no net increase in production compared with the High P treatment. Only tentative conclusions can be made at this time since the pasture is considered to be still in a development phase. However, results suggest that application of P only to south aspects and moist north slopes, and for steep, north-facing slopes to receive N, plus only limited P, will be the most efficient fertiliser policy. Keywords: dry hill country, phosphate response, nitrogen response, pasture production, slope, aspect
Special management aspects of farming pakihi
BRENT RILEY
I farm in partnership with Michelle, leasing a 218 ha dairy farm and adjoining 60 ha runoff in Collingwood, Western Golden Bay. We wintered 810 cows and 110 yearlings on the property which comprises 35% alluvial river flats and 65% pakihi. We are also 20% shareholders in a family-owned company that operates four dairy farms, one of them being the farm that we lease, the other three being run by my two brothers and their families, and my parents. One of these we have visited at Matariki on the field trip. We run a high stocking rate system of 3.6 cows/ha with high inputs and produced 245 000 kg milksolids last season. We farm in a wet environment, although we do get some sunny days. So far this season we have had 110 inches of rain, up on the average of 100 inches. Fortunately, we live on the dry side of the valley! I hope to give you an insight into farming pakihi; the process we went through to develop and establish pasture from scrub; and the changes that have occurred with time on this soil type.
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A study of farmer attitudes towards riparian management practices
T.G. PARMINTER, I.S. TARBOTTON and C. KOKICH
Transcripts from a survey of 60 farmers were analysed to identify the attitudes they held towards a range of riparian management practices, and the criteria they would use to select their most preferred practices. Most farmers had mixed attitudes towards managing the riparian area, combining aspects of "pressure farming"1, and "conservation farming"2. Pressure farming was considered to result in problems with erosion, sediment, boggy areas, and a lack of stock safety. Conservation farming was considered to be able to provide increased farming income and greater biodiversity. Farmers selected riparian management practices that they thought would reduce the problems caused by pressure farming, and obtain the benefits of conservation farming. But adoption of new technologies would take place only if the technologies were considered to be practical and not to increase management complexity. An understanding of farmers' perceptions about managing riparian areas can help policy agencies target educational interventions encouraging farmers to improve the sustainability of their resource use. Keywords: environment, extension, farmer attitudes, riparian areas, waterway management
Copper fertiliser increases pasture copper concentration and improves the copper status of grazing sheep
S.O. KNOWLES, N.D. GRACE, J.R. ROUNCE, D.M. WEST and J. LEE
Application of copper-amended fertiliser ("topdressing") increases pasture herbage Cu concentration and can increase dietary Cu intake of grazing ruminants. Animal responses to dietary Cu, in terms of changing blood and liver Cu concentrations monitored throughout the season, have not been well documented. In this study 10 experimental paddocks were topdressed with 0 (Control), 0.4 (Low) or 4.0 (High) kg Cu/ha as CuSO4.5H2O, resulting in mean herbage Cu concentrations of 8, 13 and 41 mg Cu/kg DM, respectively. The treated pastures were significantly greater than controls for at least 100 days. Romney lambs of low but not deficient initial Cu status grazing the Cu-treated paddocks for 176 days had increased Cu intake compared with controls, resulting in substantial accumulation of Cu in liver. Maximum liver Cu concentration occurred after 99 days, when the levels in low- and high-treated sheep were 3 to 12 times greater than controls (900 to 3270 vs 270 mg Cu/kg fresh tissue). No changes in blood plasma Cu concentration were observed. A predictive relationship between pasture Cu and liver Cu concentrations of grazing lambs was determined, and recommendations for sheep Cu supplementation via Cu topdressing are made. Keywords: copper status, copper supplementation, liver biopsy, Romney lambs, topdressing
Copper supplementation of grazing cattle using pasture topdressing and individual animal treatment
D.M. WEST and N.D. SARGISON
Three methods of copper supplementation were compared in 9- to 15-month-old Friesian bulls on a farm with a history of copper deficiency. A group of 60 bulls grazed 19 ha which had been topdressed in May with 120 kg copper sulphate (6.3 kg/ha). Five of the bulls were identified for repeated sample collection. A second group of 60 bulls grazed an untreated area and five of these were each given a 20 g copper capsule (Cuprax), five were injected with 100 mg calcium copper edetate (Coprin) and five were not supplemented with copper and served as controls. The response to supplementation was assessed by monitoring liver copper concentrations of the designated five bulls in each treatment plus the five control bulls at 34, 78, 121, 197 and 314 days after treatment. Pasture copper concentrations increased on the topdressed area from 12 to 25 ppm DM for 6 weeks and subsequently remained at 10 ppm for the remainder of the trial. Pasture molybdenum concentrations were low (0.3–0.5 ppm DM) initially and rose to 1.0–1.2 ppm DM during spring on both grazing areas. Despite the elevation of pasture copper, liver copper concentrations of the bulls grazing the topdressed pasture declined in a similar way to the controls. However, at slaughter, day 314, the bulls grazing the copper topdressed area had higher liver copper concentrations than the controls (P = 0.099). Copper capsules resulted in a significant elevation of liver copper concentration throughout the trial. Copper calcium edetate injection did not significantly increase liver copper concentrations. More information on the factors affecting copper uptake by grazing ruminants is required. Keywords: cattle, copper deficiency, dietary supplements
Development of sulla (Hedysarum coronarium) for better adaptation to grazing
G.B. DOUGLAS, R.G. KEOGH and A.G. FOOTE
Sulla is potentially useful in New Zealand as a forage for grazing, hay and silage, in addition to its established use for soil conservation. The plant produces up to 25 t DM/ha/year and is a highly nutritious feed; it contains condensed tannins (CT) which prevent bloat and improve protein utilisation; and high livestock utilisation of leaf and stem is possible. Established stands of sulla can be maintained for several years under good management, but there have been many reports of poor persistence. In an effort to improve stand persistence, particularly under grazing, two evaluations were conducted near Palmerston North in 1995–97. Trial 1 screened 32 lines of sulla, including commercial cultivars, for a range of morphological attributes (e.g., habit, height, spread, vigour, herbage mass), whereas Trial 2 assessed similar attributes for 134 plants of cv. Grasslands Aokau, involved in an earlier grazing trial. Foliar levels of extractable CT were also determined in Trial 1, which is the first documentation of CT variation in the species. In both trials, plants survived for up to 2.5 years and seed was collected from 145 (Trial 1) and 31 (Trial 2) selected plants in early 1997. The plants selected typically had prostrate growth habit, moderate to high plant diameter and branch number, and high plant vigour. CT levels, assayed by a vanillin/HCl procedure, averaged 1.2–3.5% DM in most lines and were 36–81% higher for six samples assayed by a butanol/HCl method. Some CT levels may be sufficiently high to have a slight nutritional disadvantage to ruminants, but this could potentially be overcome by growing sulla with non- CT containing forages. Progeny from selected plants in each trial are being evaluated under more frequent grazing, and their seed will be harvested in autumn 1999. Keywords: condensed tannins, cultivars, Hedysarum coronarium, legume, persistence, sulla
Effect of date and length of closure and post grazing residual on pasture quality for silage
J.M. MCGRATH, J.W. PENNO, K.L. DAVIS and R. WRENN
The nutritional value of pasture silage made in New Zealand is often sub-optimal for lactating dairy cows. As farming systems require more pasture silage to be used in an attempt to increase lactation lengths and milksolids production per cow, the quality of this silage becomes more important. In spring 1995, pastures were closed for silage at weekly intervals from 11 September to 17 October, representing six distinct closure dates, to determine the effect that date and length of closure has on pasture quality. In spring 1997 pastures were grazed to different residuals (1.2– 1.4, 1.8–2.0, 2.1–2.4 and 2.5–2.9 t DM/ha) and then closed for silage to determine the effect that post grazing residual has on pasture quality. In both experiments pasture dry matter (DM) yield and chemical and botanical composition was monitored over the 63 day closure. Pasture closed on 11 or 17 September had higher metabolisable energy (ME) (P<0.05), organic matter digestibility (OMD) (P<0.01) and DM yields at 70% OMD than pasture closed after 9 October. Pasture closed on 11 September remained above 70% OMD for the 63 day closure while pasture closed on 17 October reached 70% OMD after only 49 days. Pasture grazed to 1.2–1.4 t DM/ha accumulated significantly less DM to 42 days post grazing than all other grazing treatments (P<0.001), but had higher crude protein (CP), OMD and ME contents (P<0.001). The low post-grazing residual resulted in pasture with more vegetative (P<0.001) and less reproductive (P<0.05) material at 42 days post grazing. These results suggest that in order to maximise the yield of pasture silage of suitable feed quality for lactating cows pasture should be last grazed before 15 September, harvested before the end of November and have a post grazing residual of approximately 1500 kg DM/ha. Keywords: closure date, closure length, herbage accumulation, organic matter digestibility, pasture quality, pasture silage, perennial ryegrass, postgrazing residual
Effect of increasing elemental sulphur and copper intakes on the copper status of grazing sheep
N.D. GRACE, J.R. ROUNCE, S.O. KNOWLES and J. LEE
Under some conditions, the use of high-sulphur fertilisers has been thought to be associated with an increase in the incidence of copper deficiency among ruminants grazing the fertilised pastures or fed treated herbage. In this study 35 Romney lambs grazing ryegrass–white clover pasture of low molybdenum content (<0.5 mg Mo/kg DM) received dietary supplements of elemental S and Cu 3 times weekly for 15 weeks. The supplements increased S intake from 3.9 to 7.9 g/day, and increased Cu intake from 9.3 to 24.3 mg Cu/day. Treatment with S significantly increased the total S concentration in strained rumen fluid (SRF), and treatment with Cu increased the Cu concentrations in all fractions of the digesta. In the presence of 4 g S/day, the effect of supplemental Cu on SRF and duodenum soluble Cu concentrations was reduced by about half. Increasing S intake had no effect on plasma and liver Cu concentrations, while increasing Cu intake markedly raised liver Cu concentration. It was concluded that fertilising pastures with elemental S is unlikely to affect the Cu status of grazing sheep, under conditions where pasture Mo concentration is low (<0.5 mg Mo/kg DM). Keywords: copper, fertiliser, liver, plasma, Romney, sulphur
Effect of sward height during lactation on heifer and calf performance
B.M. PEACHEY and S.T. MORRIS
The study compared the performance of Hereford x Friesian heifers and their calves managed on a Low (58±0.5 mm sward height) (L) or High (107±1.4 mm sward height) (H) pasture cover from calf birth up to weaning at about 90 days over spring 1997. Milk production was measured at days 29 and 65 of lactation using the weigh-nurse-weigh technique. At day 29 the heifers on L had dropped by 0.20 condition score units compared with those on H which increased (P<0.001) condition score by 0.32 units; however, by the end of the trial there was no difference in score between the two treatment groups. Sward height significantly affected milk production at day 65 (P<0.05), the High treatment group producing 24% more milk than the Low (8.7 vs 7.0 kg/cow,). There was a corresponding difference (P<0.001) between ADG of the calves on the L (0.95 kg/day) and the H (1.24 kg/day) treatments from day 65 till weaning. Sward height had little effect on heifer and calf during early lactation. This suggests that under adverse conditions farmers could restrict lactating heifers for the first 65 days of lactation, when they are at a condition score of 3.0 or better, without adversely affecting dam or calf performance. This has practical implications for the date of calving and for feed planning on farms where beef breeding cows are usually run in conjunction with a ewe flock. Keywords: beef cattle, body condition score, calf growth, lactation, sward height
Effects of soil fertility on the persistence of dryland cocksfoot and tall fescue pastures
D.R. SMITH, T.J. FRASER, C.A. MOFFAT and M.J. DALY
The persistence of pastures sown with tall fescue, cocksfoot or mixtures of the two species was evaluated by tiller core measurements on 106 paddocks that had been sown in 1989 or 1991 on dryland east coast sheep/beef farms. In both North and South Island paddocks, cocksfoot was the dominant grass in mixtures of tall fescue and cocksfoot. Tall fescue presence was usually much lower than that of ryegrass and other unsown grasses, regardless of sowing mixture. High levels of cocksfoot were associated with low levels of ryegress, browntop and other perennial grasses. North Island paddocks had higher P levels (Olsen P=25) than South Island paddocks (Olsen P=21) but had lower levels of clover (32%) and higher levels of browntop (26%) than South Island paddocks (52% clover, 13% browntop). In North Island paddocks sown with cocksfoot, there were weak, negative associations of white clover with fertiliser N inputs (r = -0.45) and soil P levels (r = - 0.41). These effects of P and N on clover appeared to be owing to increased cocksfoot dominance at high fertility. In the North Island, the best white clover presence was found in pastures that were low in cocksfoot but high in ryegrass, browntop and other unsown perennial grasses. In the South Island there was no significant association of clover with soil test levels or fertiliser history. Comparison of 1996 measurements made on North Island paddocks with 1991 measurements on the same paddocks indicated that establishment effects could have long-term effects on the persistence of tall fescue and cocksfoot. Inclusion of cocksfoot in the seed mix reduced tall fescue persistence. High levels of perennial ryegrass at establishment were also associated with poor tall fescue persistence. These effects appeared to be more important than soil fertility constraints in reducing tall fescue persistence. The presence of other vigorous grasses, such as ryegrass, during establishment may also reduce or delay cocksfoot dominance and thus improve white clover persistence. Keywords: cocksfoot, dryland, pasture persistence, soil fertility, tall fescue
Elite selection of tagasaste (Chamaecytisus palmensis) for droughtprone sites
G.B. DOUGLAS, D.R. WOODFIELD and A.G. FOOTE
Tagasaste (tree lucerne) is a drought-tolerant, shrub/ tree legume which is naturalised in many parts of New Zealand. It is a potentially useful supplementary forage for sheep and cattle, particularly in summer and early autumn. Tagasaste is highly variable for a range of attributes and in the 1980s, 16 lines were identified which had improved production, habit, and frost and disease tolerance. From 1993 to 1996, this germplasm was evaluated for morphological and chemical attributes at two sites in the lower North Island – Onga Onga, central Hawke's Bay (Trial 1) and Bulls, Rangitikei (Trial 2) – to select material for release. Differences in survival and growth of the lines between sites were the major finding. Average plant survival of lines in Trial 1 was higher than in Trial 2 (89 vs 58%), whereas growth of lines in Trial 2 exceeded that in Trial 1, for example for plant height (274 vs 168 cm), plant width (325 vs 168 cm), root collar diameter (91 vs 58 mm) and total plant dry matter (15.6 vs 6.7 kg/plant). The total N content of lines in Trial 2 was 25% higher than in Trial 1 (33 vs 26 g N/kg DM) whilst in vitro digestibility of herbage from all lines at each site was 75%. Two lines, AL2244 and AL2432, which had high survival at both sites, and means for other attributes which were similar to or exceeded the site mean for all lines, were selected to comprise the final release. Seed of these lines is being increased. Keywords: browse shrubs, Chamaecytisus palmensis, drought fodder, dryland legumes, revegetation, selection
Frequent grazing by sheep reduced caucasian clover cover and rhizome mass in ryegrass pasture
R.J. LUCAS, A.J.E. MOORHEAD, W.W. NICHOL, J.R. SEDCOLE and P. JARVIS
The responses of hexaploid caucasian clover (Trifolium ambiguum) to four contrasting grazing regimes were compared with those of white clover (T. repens) in an endophytic (Neotyphodium lolii) hybrid ryegrass pasture on a fertile lowland site. After 2 years, frequent grazing (set stocking) by sheep reduced caucasian clover cover to 10% compared with 25.5% in infrequent grazing (rotational grazing) treatments (mean spelling time 25 days). Similarly, frequent grazing reduced caucasian clover rhizome plus root dry weight (780 kg DM/ha when sampled to 100 mm depth in frequently grazed plots, compared with 3220 kg DM/ha for infrequent). Under frequent grazing treatments, mean white clover cover was 21%, under infrequent hard grazing it was 26% and under lax infrequent grazing it was 14%. The reduction in ryegrass tiller population from 5720/m2 in the infrequently and laxly grazed treatments to 4150/ m2 in the frequently hard grazed pastures indicated the severity of that hard grazed treatment. These results show that in lowland ryegrass pastures on high fertility sites, the stoloniferous growth form of white clover may be superior to the rhizomatous strategy of caucasian clover when grazing by sheep is frequent throughout spring, summer and autumn. Keywords: caucasian clover, cover, grazing frequency, grazing intensity, kura clover, rhizomes, ryegrass, Trifolium ambiguum, Trifolium repens, white clover
Genetic variation for rate of establishment in caucasian clover
K.H. WIDDUP, T.L. KNIGHT and C.J. WATERS
Slow establishment of caucasian clover (Trifolium ambiguum L.) is hindering the use of this legume in pasture mixtures. Improved genetic material is one strategy of correcting the problem. Newly harvested seed of hexaploid caucasian clover germplasm covering a range of origins, together with white and red clover and lucerne, were sown in 1 m rows in a Wakanui soil at Lincoln in November 1995. After 21 days, the caucasian clover material as a group had similar numbers of emerged seedlings as white clover and lucerne, but was inferior to red clover. There was wide variation among caucasian clover lines (48–70% seedling emergence), with the cool-season selection from cv. Monaro ranked the highest. Recurrent selection at low temperatures could be used to select material with improved rates of seedling emergence. Red clover and lucerne seedlings produced significantly greater shoot and root dry weight than caucasian and white clover seedlings. Initially, caucasian clover seedlings partitioned 1:1 shoot to root dry weight compared with 3:1 for white clover. After 2 months, caucasian clover seedlings had similar shoot growth but 3 times the root growth of white clover. Between 2 and 5 months, caucasian clover partitioned more to root and rhizome growth, resulting in a 0.3:1 shoot:root ratio compared with 2:1 for white clover. Both clover species had similar total dry weight after 5 months. Unhindered root/ rhizome devel-opment is very important to hasten the establishment phase of caucasian clover. The caucasian clover lines KZ3 and cool-season, both selections from Monaro, developed seedlings with greater shoot and root growth than cv. Monaro. KZ3 continued to produce greater root growth after 5 months, indicating the genetic potential for improvement in seedling growth rate. Different pasture estab-lishment techniques are proposed that take account of the seedling growth characteristics of caucasian clover. Keywords: establishment, genetic variation, growth, seedling emergence, Trifolium ambiguum
Image analysis techniques to characterise white clover root morphology
DEBBIE CARE1, SHIRLEY NICHOLS1 and DEREK WOODFIELD2
The use of low-ionic-strength hydroponic culture and image analysis techniques to discriminate and isolate morphologically distinct, genetically differentiated root types within white clover is described. Advantages of this method include the ability to view the genetic expression of the root systems without the modifying effects of growth in soil, to examine the growth and structure of roots over time, and to store the images for further examination. It is recognised that although the root systems grow in three dimensions, they are constrained to two dimensions by the flatbed scanner. However, the morphological parameters determined by image analysis would not be altered whether this analysis was measured in two or three dimensions. Keywords: image analysis, root morphology, solution culture, Trifolium repens
Influence of pasture allowance on the composition and cheese-yielding potential of milk.
M.J. AULDIST, W. VAN DER POEL, P. LABOYRIE and C.G. PROSSER
Effects of pasture allowance on the yield, composition and cheese-yielding potential of milk were investigated using 48 Friesian cows in crossover experiments during spring (~60 days after calving) and summer (~180 days after calving). All cows were subjected to two nutritional treatments: ad lib. grazing (pasture allowance >45 kg DM/cow/day) and restricted grazing (16–18 kg DM/cow/day). Milk samples were collected from each cow on the final day of each treatment period and analysed for a range of components. Pasture dry matter intakes (DMI) during treatment periods were determined using the n-alkane technique. Increasing pasture allowance resulted in increased DMI. Cows grazing ad lib. had higher milk yields, concentrations of protein (spring only), casein, whey protein (spring only), casein:whey protein ratio (summer only), α-casein, β-casein and urea, but lower concentrations of serum albumin and immunoglobulin, than cows grazing a restricted pasture allowance. Nutritional effects on milk composition were greatest in spring, at which time theoretical Cheddar cheese yields were greater for milk from cows grazing ad lib. than restricted cows. Concentrations of some milk components were correlated with DMI of cows. These results provide evidence that on-farm management practices can affect milk composition and the potential yield of dairy products. Maintaining an adequate pasture allowance for dairy cows is important not only to maximise milk production, but also to optimise the manufacturing potential of milk. Keywords: casein, cheese, milk, pasture allowance, protein
Measuring production of continuously grazed hill pastures
B.P. DEVANTIER, M.G. LAMBERT, I.M. BROOKES and C.L. HAWKINS
Estimates of pasture production are critical for comparing treatment effects in research trials, as inputs to decision support models, and for on-farm use in constructing grazing plans. We compared two techniques for measuring pasture production, over 2 years in 36 paddocks continuously grazed with sheep, on hill country at the Ballantrae Research Station. One technique (Cut method) involved harvesting pasture regrowth after trimming to a standard height. The other (Model method) calculated pasture production as the sum of grazing animal intake (estimated using a spreadsheet-based model with inputs including animal performance and pasture quality) and changes in pasture cover (above-ground biomass). Annual pasture production estimates were reasonably well correlated (R2 = 0.66), but those using the Cut method were 55% greater than using the Model method. Agreement was best in spring and summer, and poorest in autumn and winter. Factors contributing to these discrepancies included the contrasting starting conditions for the pasture at the start of each measurement period (shorttrimmed for the Cut method, and patch-grazed for the Model method); the effect of grazing in the Model method maintaining pastures in a more vegetative state; and the greater losses from senescence and decay in the Model method pastures. The potential for errors using the Model method was high where measurement periods were short, as accuracy of measurement of pasture cover can be suspect. The Model method probably better quantified net pasture production in grazed pastures. Keywords: grazing, hill pasture, intake, model, pasture production
Preliminary observations of Osmia coerulescens as a pollinator of herbage seed crops
R.G. PURVES, P.T.P. CLIFFORD and B.J. DONOVAN
The availability of large numbers of pollinators is critical to the efficient seed production of crosspollinated species of herbage legumes. The honey bee is the predominant pollinator of crops in New Zealand. There are risks in being solely dependent on the honey bee for pollination. Honey bee diseases and mites have reduced bee numbers in many parts of the world. The floral morphologies of some species such as tetraploid red clovers and lucerne are unsuited to pollination by honey bees. Other than in some localised areas, alternative pollinators have had little impact on improving pollination of these species in New Zealand. In 1995, Osmia coerulescens L. was introduced into New Zealand to be evaluated as an alternative, managed pollinator for herbage seed crops. Results from the 1997/98 season show that O. coerulescens can be stored at 2–3°C with low mortality until the bees are 9 months old. When stored to 10.5 months of age, reproductive vigour was lost and mortality was high. The potential multiplication rate of this bee is high, especially in the first generation of a season. Managing the bees to emerge during summer rather than spring as occurs naturally had no effect on bee reproduction. The bee also successfully reproduced when retricted to white clover flowers as the only source of pollen and nectar. The wasp parasitoid Melittobia spp. destroyed large numbers of developing bees resulting from the nesting of 2nd-generation bees. Control of Melittobia spp. is discussed. Keywords: management, Melittobia spp., Osmia coerulescens, pollination
Reproductive potential of caucasian clover at four locations within New Zealand
R.G. THOMAS1, K.H. WIDDUP2, K. PANKHURST3 and D. RYAN4
Seedlings of KZ2 caucasian clover (Trifolium ambiguum) were grown at 4 sites within New Zealand (Kerikeri 36°S, Palmerston North 40°S, Lincoln 43°S and Gore 46°S) where they received natural daylight and temperatures during 1997. Northernmost plants produced more vegetative primary crown shoot buds than southernmost. In the first growing season numbers of flowering shoots formed per plant were: K 17.9, P 10.0, L 10.2 and G 5.7. In spring of the second growing season, mean numbers of primary crown flowering shoots per plant at peak flowering in December 1997 were: K 19, P 30, L 55, G 20. Fewer flowering shoots formed at upturned rhizome tips. Daylength was not the major factor controlling flowering, the results instead supporting the hypothesis that low temperatures provided the main flowering stimulus. Lincoln was the best of the four locations overall for flowering shoot production. Fewer flowering shoots at Gore probably resulted from slower growth in cooler conditions. Poorer flowering at Kerikeri in the second season might have resulted from the warmer northern winter or been linked to the overproduction of vegetative buds in the first season. Stronger flowering at Kerikeri during the first season raises the possibility, though, of growing caucasian clover as an annual crop for seed production in Northland if sown early in spring. Keywords: caucasian clover, daylength, flowering, low temperature, seed production, Trifolium ambiguum
Rhizobium issues affecting the contribution of caucasian clover to New Zealand pastoral agriculture
R.M. ELLIOT, H.J. MCINTYRE, B.C. CHALLIS, H.N. PRYOR, W.L. LOWTHER and C.W. RONSON
Caucasian clover (Trifolium ambiguum) is being commercially released for use in New Zealand agriculture. Seed must be inoculated at sowing, as caucasian clover forms a nitrogen-fixing symbiosis only with specific rhizobia that are not native to New Zealand. These rhizobia have the potentially undesirable property of readily forming nodules on white clover that do not fix nitrogen. Caucasian clover inoculant strains available for use in New Zealand were found to be genetically unstable in the laboratory, and must be frequently monitored for their symbiotic properties. A strain of caucasian clover rhizobia that gives better establishment and growth of caucasian clover under oversowing conditions was identified. This strain maintained a higher level of viability under stress conditions in the laboratory and showed enhanced survival on seed in the environment. Growth of caucasian clover results in large populations of caucasian clover rhizobia in the soil. These formed nodules on white clover in the same field environment, although white clover rhizobia dominated nodule formation. Nevertheless it is possible that present caucasian clover inoculants may over time reduce nitrogen fixation and hence the production and persistence of white clover. Further research is required to develop a caucasian clover strain that does not form ineffective nodules on white clover. Keywords: caucasian clover, inoculation, nodulation, rhizobia, Trifolium ambiguum, Trifolium repens, white clover
Standardisation between livestock classes: the use and misuse of the stock unit system
WARREN J. PARKER
The stock unit (SU) system is used extensively in New Zealand agriculture. These applications include inter- and intra-farm comparisons, rural lending and valuation, and farm system design and analysis. The livestock classes and performance levels to which SU conversion factors are applied has increased significantly since Professor Coop defined the ewe equivalent (EE) system, and now includes deer, goats and other non-conventional livestock species. This has led to a proliferation of SU values and their incorrect application and interpretation, especially in between-farm comparative analysis. Benchmarking provides a more economically rational way of improving the profitability of livestock farms than the use of standards based on SUs. Obtaining agreement on the specifications of animal-pasture-financial models to allow users to derive substitution rates between stock classes according to their farm's resources and management practice is preferred to publishing national standards for SUs. Keywords: comparative analysis, livestock classes, standardisation, stock unit
Survival of endophyte-free perennial ryegrass after autumn spray/ drilling in the Waikato
V.T. VAN VUGHT and E.R. THOM
The persistence of an endophyte-free ryegrass (Lolium perenne L.) pasture established by autumn spray/drilling was studied over two years at the Dairying Research Corporation, Hamilton. Main plots were sprayed with glyphosate at 1.44 kg a.i./ ha (4 l/ha of Roundup G2) in mid March 1996 (S), or mid March and again in mid April (D). White clover (Trifolium repens L.) was removed from half the area of each main plot using herbicide and the remainder was drilled with white clover. All plots were direct drilled with endophyte-free peren-nial ryegrass in late April. Plots were rotationally grazed by dairy cows. Double spraying killed germinating volunteer ryegrass, Poa species and weeds, almost doubling the ryegrass content of D compared with S plots in the first winter/spring, and maintaining an advantage over the first year from drilling. Plants were larger in D than S over the first winter/spring, contributing to about a 10% improvement in their survival, reducing to about 5% by March 1998. Sown-plant densities were 200–250/m2 by April 1998, similar to those found in high-endophyte pastures. Double spraying reduced the clover content of +Cl plots to similar levels as those in -Cl plots, lowering the potential herbage accumulation for D. Double spraying before drilling had a transitory effect on seasonal herbage accumulation, and no effect on overall herbage accumulation. Keywords: dairy pastures, endophyte, persistence, plant competition, ryegrass, tillering, white clover
Tall fescue and chicory for increased summer forage production
M.D. ROLLO, G.W. SHEATH, M.W.A. SLAY, T.L. KNIGHT, T.G. JUDD and N.A. THOMSON
Production of summer forage is an important consideration in environments prone to extremes of heat or moisture stress. Tall fescue (Festuca arundinacea) and chicory (Cichorum intybus) are two forage species with the potential to overcome the production shortfalls of perennial ryegrass (Lolium perenne) in such environments. Trials from three New Zealand regions prone to summer drought (Taranaki, Hawke's Bay and Canterbury) were used to compare production of tall fescue and chicory with production from resident ryegrass. Consistent production advantages from tall fescue and chicory were evident in the two years after establishment. Potential production advantages can disappear in subsequent years when summer moisture levels are very high or very low, or temperatures extremely high. Moderate moisture levels in summer, indicated by moderate ryegrass production, gave the biggest relative summer production advantages to tall fescue. Keywords: chicory, dryland, forage production, ryegrass, tall fescue
The clover root weevil in northern pastures: on-farm observations of its impact on white clover
J.P.J. EERENS, B. WILLOUGHBY, F. KETTLEWELL, S. HARDWICK and S. BAY
The clover root weevil (CRW) (Sitona lepidus) has had, over the last two years, a major impact on pastoral farming in the greater Waikato area. Research into CRW biology, damage profile and financial impact is continuing and far from complete. A survey of farms in the affected areas in 1997/98 yielded a large volume of on-farm observations. A survey of the impact of CRW on clover on a single farm produced data that estimated the cost of CRW to this farming operation. These anecdotal findings are combined with initial results from a glasshouse experiment. Damage by CRW tended to be less on lighter (ash and pumice) soils than on heavier, more water-retentive (peat and clay) soils. Drought reduced CRW egg survival and the ratio of first instar larvae to number of eggs hatched. Damage was greater under hard than lax defoliation regimes and increased with increasing rates of mineral nitrogen application. Red clover appeared to be less affected by CRW than white clover. The general picture suggested that the level of stress placed on the clover plant played a major role in the impact of CRW on those clover plants: the higher the stress levels the greater the impact of CRW. Keywords: clover root weevil, farm survey, pasture pest, Sitona lepidus, Trifolium repens, white clover
Thinopyrum intermedium (Host) Barkw. & Dewey – a review, and evaluation of intermediate and pubescent wheatgrass for dryland agriculture in New Zealand
B.J. WILLS1, G.B. DOUGLAS2, J. McKENZIE3, K.D. TRAINOR1 and A.G. FOOTE2
Intermediate and pubescent wheatgrasses (Thinopyrum intermedium) are potentially useful as dryland forage grasses in New Zealand. The recent literature on their international and local use in pasture and cropping situations is reviewed. Under semi-arid conditions at Bendigo Station over a 13-year period, cv. Luna wheatgrass has spread several metres from the original drill lines and it provides very high ground cover. In terms of dryland soil resource conservation this contrasts with adjacent cocksfoot and, to a lesser extent, lucerne plots which have wide-spaced plants interspersed with litter and much bare ground. In a mixed drilling containing wheatgrass, hairy dorycnium, birdsfoot trefoil and sheep's burnet, the first two species now dominate. At Takapau, central Hawke's Bay, annual yields from intermediate and pubescent wheatgrasses produced over 80% of the yield of 10 New Zealand cultivars in spring, summer and autumn, and 65% in the winter. Of the wheatgrasses, cv. Topar intermediate wheatgrass and a pubescent wheatgrass (unnamed line) were the lowest yielding, whereas cv. Oahe and cv. Mandan produced the highest yields. Cv. Greenleaf pubescent wheatgrass had higher foliar nitrogen content than all other species, but in vitro organic matter digestibility was less than 700 g OM/kg DM. Although the wheatgrasses had satisfactory herbage yield and nutritional value, better alternative species are available for pastoral farming in central Hawke's Bay. On Belfield in the Hakataramea Valley, cv. Rush has been the most vigorous wheatgrass for establishment and it seems to handle cold winds and frost well. Hay made from a wheatgrass/ lucerne mix is considered better than that from the individual species as this can increase production by 40–50%, depending on soil and climatic conditions. Usually only one cut per year is taken from the mixed pasture. Crop maintenance includes the application of 200 kg/ha of sulphur super extra every 3–4 years and the pH is maintained at about 5.9–6.4 by liming. A significant advantage is that no stock health, pest or plant disease problems have been noted as yet with any of the wheatgrass varieties available in New Zealand. Keywords: dryland agriculture, New Zealand, Thinopyrum, wheatgrass
Winter beef weight gain on Italian grass seed crops in South Canterbury
M.D. CRAIGHEAD, J.A. HAYWARD and W.B. BURGESS
Italian grass seed crops grown in South Canterbury were used as intensively grazed winter greenfeed for weaner Angus or Angus cross steers in 1994– 1996. The aim was to achieve good liveweight gain between April and October and in the process control the excess bulk on the crop. thereby spreading the economic risk associated with relying on the crops income coming from seed. Over this period, liveweight gains of 0.9, 0.9 and 1.0 kg/head/ day were achieved. Cattle were sold in early October to coincide with spikelet initiation, the optimum time to close the crop for seed. This enabled us to supply cattle on contract to a market prepared to pay a bonus for animals at the right weight and age. The crop was sown earlier than normal to build up a bank of feed ahead of the steers. Steers were shifted twice daily and backfenced to allow regrowth and the use of nitrogen fertiliser. Pasture quality and supply was closely monitored to optimise intake. Seed yields were maintained at about 1200 kg/ha during the three years. Keywords: Angus steers, grass seed production, Italian ryegrass, liveweight gain, nitrogen fertiliser, pasture growth, pasture quality, pasture utilisation