Defoliation patterns and tillering dynamics in Italian ryegrass under different herbage allowances
This work was carried out in order to generate information on the tillering process and to contribute for the understanding of the defoliation process on Italian ryegrass (Lolium multiflorum Lam.) grazed by lambs under different herbage allowances: 6, 8 and 12 kg of dry matter per 100 kg of animal live weight per day. The grazing method was intermittent. The experimental design was completely randomized following a repeated measure arrangement, with three treatments and two area replications. The intensity of defoliation is greater at 6 and 9% herbage allowances. The defoliation interval is higher at 12% herbage allowance, intermediate at 9% and lower at 6%. The rates of tiller emergence, survival and death, stability index the tiller population are similar for the different herbage allowances and differ according to the phenological stage of ryegrass. Structural changes caused by canopy management with low herbage allowance and/or due to the advance in developmental stage of ryegrass alter defoliation strategies, with more intense and frequent grazing.
Energy flows and organic reserves of forage plants
This review addressed the existing energy flows in the pasture ecosystem, as well as the use of organic reserves by forage grasses. The radiant energy is absorbed by the leaves and transformed into chemical energy by which the assimilated carbon is fixed. During the process of assimilation and fixation of C, photochemical, and biochemical processes are carried out, which are influenced by light. Several environmental factors can influence the ability of plants to respond to stimuli. In this sense, energy flows within the pasture system are in constant movement to maintain the forage plant. The direction of energy flow varies with the growth environment of the forage plant, since in addition to affecting the structural characteristics, the environmental factors exert control over the root system. In theory, organic reserves located in roots and stems play a crucial role in the growth of grazed plants, especially in the first days after defoliation. Therefore, it is important to encourage research involving the reserve organs and their accumulation patterns so that the results can assist in the development of sustainable grazing systems.
Características morfogênicas de azevém anual (Lolium multiflorum Lam.) sob pastejo em sistemas intensivos de utilização
The experiment was carried out to characterize the morphogenic response of Lolium multiflorum cv. "Comum" in intensive utilization systems using nitrogen (N) fertilizer range from 90 to 180kg.ha-1 of N, in mixture or not with Arrowleaf Clover. The experiment was conducted in an area of the Department of Animal Science of the Universidade Federal de Santa Maria, Brazil, from July 20th to September 23th, 2002. Beef heifers were used in continuous grazing with variable stocking rate using put and take technique for the adjustment of the stocking rate to a herbage allowance of 10% of the live weight. To evaluate the dynamics growth of the species, the marked tillers techniquewas used. The experimental design was complete randomized with 63 repetitions. The following treatments were used: italian ryegrass + oat + 180kg.ha-1 of N (N180); italian ryegrass + oat + 90kg.ha-1 of N + supplementation (N90+S); italian ryegrass + oat + 120kg.ha-1 of N + arrowleaf clover (N120+AC). The animals of the treatment N90+S were supplemented with ground sorghum grain at 1% of the live weight. The leaves appearance rate (LAR), leaves elongation rate (LER) and leaves lifespan (LL) were evaluated. Treatments receiving the highest N level (N180 and N120+AC) had in the first period higher LER. The treatment N90+S showed similar result (4,95 mm.tiller-1.day-1) only in the second period. In an average of two periods, there was not a significant difference between treatments. The treatment N120+AC had larger LL and lower LAR in the first period than the others, and it didn't differ of these in the last period. In conclusion, intensive systems of utilization of sward with levels from 90 to 180kg.ha-1 of N, in mixture or not with Arrowleaf Clover in grazing conditions, didn't affect the morphogenic characteristic of ryegrass.