Differences in height and mass of massaigrass pastures in silvopastoral systems with different arboreal spacings

The success of animal production in silvopastoral systems requires careful planning to maintain a balance among soil, trees, forage and livestock. Forage production can be affected by shading caused by trees, due to a decrease in the incident radiation and spectrum ratio of light. Thus the study aimed to quantify the differences in height and mass of massaigrass pastures (Panicum maximum x Panicum infestum) in silvopastoral systems in different arboreal spacings grazed by adult sheep under intermittent stocking. The experiment was conducted at FCAV, UNESP, Jaboticabal, SP, in three cycles of grazing: February 17 to March 6, March 10 to 27 and July 16 to 31, in 2015. The treatments consisted of two spacing among eucalyptus trees (Eucalyptus urophylla x Eucalyptus grandis), with 6.0m x 1.5m in E6 silvopastoral system and 12.0m x 1.5m in E12, and a treatment that remained treeless (TL).The massaigrass light interception of 95% was used for adult male sheep with 22.5 kg initial BW start grazing where remained until 20cm of pasture height. The experimental design was completely randomized with three treatments (E6, E12 and TL) and six replicates (paddocks). Data were submitted to variance analysis considering the effects of treatments, cycles, and interaction, using proc mixed from SAS, and the level comparisons for cycles were made using orthogonal polynomial contrasts (P <0.05) and Tukey's test for treatments (P <0.05).There was a significant difference among treatments for sward height (SH), total forage mass (TFM), green forage mass (GFM) and green mass:dead mass ratio (G:D) in both pre and post grazing, in all cycles. The lower values were observed for the E6, as a consequence of higher shadow, in relation to other treatments. On the other hand, no difference was observed between TL and E12. In relation to cycles, SH, TFM, and GFM presented a quadratic effect, while dead forage mass (DFM) and G:D presented a linear effect. The reduction of SH and GFM and the increase in DFMin July, can be explained by reduced photoperiod, precipitation and average temperature in the third cycle (winter season in the tropics). Besides the effect of shadow in forage production, the results obtained herein showed that the tree arrangement of E12 does not adversely affect the growth of massaigrass.