Herbage Productivity and Botanical Composition of Hill Pasture as a Function of Clipping and Site Features
Complex topography and varied soil of hill-land pastures create microsite conditions that support an array of floristic associations and herbage production patterns. This complicates management for forage and livestock production because the seasonal distribution and quantity of forage vary. Our objective was to determine herbage production and floristic composition of a hill pasture as a function of site characteristics and canopy management. An existing 3-ha hill pasture watershed was oversown with white clover (Trifolium repens L.) and orchard-grass (Dactylis glomerata L.) and fertilized with reactive phosphate (PO 4 ) rock (PR). Replicated plots on each of four sites were clipped once (stockpiled), twice (hay harvest), or three times (long rotation) annually. Site had a significant impact on cumulative herbage production, whereas the influence of clipping was mixed. The least (1.9 Mg ha -1 ) amount of herbage production in a given season occurred on a northeast (NE)-facing site and the greatest (4.6 Mg ha -1 ) in a natural drainage area (ND) traversing the pasture. Herbage production increased by about 80% with overseeding and PR, but the relative ranking of production among sites stayed the same. Botanical composition was also strongly influenced by site, with velvetgrass (Holcus lanatus L.) predominating in ND and red fescue (Festuca rubra L.) occurring primarily on the NE site. The stockpiled treatments became dominated by grasses and weeds 4 yr after treatments were imposed, regardless of site, and were similar to the least productive site (NE-facing) in the pasture. Our results suggest that application of amendments to the more productive portions of a site are likely to have greater return.
Grazing effects on the nutritive value of dominant species in steppe grasslands of northern China
BackgroundForage nutritive value plays an important role in livestock nutrition and maintaining sustainable grassland ecosystems, and grazing management can affect the quality of forage. In this study, we investigated the effects of different grazing intensities on the nutritive values of Leymus chinensis (Trin.) Tzvelev, Artemisia spp. and Carex duriuscula C. A. Mey in the steppes of China during the growing seasons from 2011 to 2013. Five grazing management treatments were implemented: (1) rest grazing in spring, heavy grazing in summer and moderate grazing in autumn (RHM), (2) rest grazing in spring, moderate grazing in summer and heavy grazing in autumn (RMH), (3) heavy grazing though all seasons (HHH), (4) heavy grazing in spring and summer and moderate grazing in autumn (HHM) and (5) continuous moderate grazing in all seasons (MMM).ResultsThere were significant effects of year, season, treatment, and year × season and year × treatment interactions only on the crude protein of L. chinensis (P < 0.05). The crude protein concentrations of L. chinensis in the plots of constant high grazing pressure (HHH) and reduced grazing pressure in the last grazing stage (HHM) were higher than with deferred grazing (RMH and RHM, P < 0.05) in spring from 2011 to 2012. For Artemisia spp. and C. duriuscula, the crude protein concentration in HHH was higher than that in RMH (P < 0.05) in the summer of 2011. There were no significant differences (P > 0.05) for ether extract, neutral detergent fiber, acid detergent fiber and Ca concentration for any of the grasses in spring and summer from 2011 to 2013 under the different grazing management treatments.ConclusionsThe nutritive value of L. chinensis was more responsive to grazing disturbance than Artemisia spp. and C. duriuscula, and heavy grazing maintained a relatively high crude protein content in all species. Seasonal and interannual seasonal differences in grazing management combinations were two of the most important factors in determining the variability of forage nutritive value, including crude protein, ether extract, neutral detergent fiber, acid detergent fiber and calcium, for L. chinensis, Artemisia spp. and C. duriuscula. We suggest that moderate grazing should be adopted to ensure the quality and yield of forage and promote the sustainable development of animal husbandry.
Influence of arbuscular mycorrhizal infection on competition between holcus lanatus and dactylis glomerata.
1 Holcus lanatus and Dactylis glomerata were grown in monocultures and mixtures to determine the influence of mycorrhizal fungi on intraand interspecific competition. 2 In monoculture, shoot biomass per plant of both species was increased over all densities by mycorrhizal infection. Increased tiller and leaf numbers per plant for H. lanatus, but not for D. glomerata, suggested that enhanced biomass was a result of greater tiller and leaf production in Holcus, but to increased tiller weight in Dactylis. Increased competition reduced shoot biomass, tiller number and leaf number in both species. 3 Although the response was variable, mycorrhizal infection generally enhanced shoot biomass of both species in mixed cultures. Tiller production in D. glomerata was generally unaffected by infection but reductions in leaf number were observed in mycorrhizal stands. In contrast to its effects on monocultures, infection had no effect on tiller production when H. lanatus was in mixture. 4 Relative yield totals (R YT) calculated for grasses grown in mixture suggest that, overall, mycorrhizal infection resulted in a reduction of resource complementarity, i.e. it increased the level of competition for the same resources. This was reflected in the relative yields which showed that the shoot biomass for each species in mixture was lower than that expected from growth in monoculture. 5 Aggressivity indices suggested that H. lanatus was more aggressive than D. glomerata when present in equal or greater numbers. Mycorrhizal infection altered the degree of aggressivity in favour of the already more aggressive plant within the combination, although, at very low densities, D. glomerata was more aggressive than H. lanatus when mycorrhizal.