Accumulation rate of mixed pastures at different defoliation frequencies

To define strategies of management in mixed pastures is important quantify the forage accumulation rate. The aim of this work was to define the defoliation frequency that optimizes the growth rate of Calopogonium mucunoides cv. Comum when mixed with Brachiaria brizantha cv. Marandu. The experimental design was randomized blocks. Three defoliation frequencies (DF), 90% (90LI), 95% (95LI) and 100% (100LI) of incident light interception and an extra treatment under free growth conditions (FG), with four replications were studied. Evaluations were conducted during two experimental periods (EP) (from 10/02/2014 to 01/20/2015 and from 01/21/2015 to 04/16/2015). Forage accumulation rate was obtained dividing the forage accumulation (difference of the pre-grazing mass of the current cycle and the post-grazing mass of the prior cycle) by regrowth interval between grazing. Responses were studied using PROC MIXED of SAS(R) and means were compared using Student's t test" (10%). Total accumulation rate of grass + legume (TARGL) and only grass (TARG) were affected by DF (P = 0.0222 and 0.0156) and EP (P = 0.0392 and 0.0339), respectively. Those two accumulation rates presented the same response pattern increasing values at the DF of 100LI and FG. Related to EP, higher values of TARGL and TARG were obtained at the first PE compared with the second. Canopies with less defoliation frequency can accumulate more stem, which was only influenced by the DF (P = 0.0009) with higher values obtained at DF 100LI and FG. Leaf accumulation rate of grass (LARG) was affected by the interaction (P = 0.0005). At the first EP, there were no significant differences among the DF and in the latter EP; greater values of LARG were observed for the canopies managed with the DF of 90LI and 95LI. However, the total accumulation rate of legumes (TARL) was affected only by EP (P < 0.0001), obtaining a mean of 5.95 kg DM ha^-1 day^-1 among the DF (P = 0.1390). According to EPs, higher TARL was found in the latter EP compared with the first. Therefore, the DF of 90LI and 95LI optimized the forage accumulation rates in mixed canopies, the largest leaf accumulation.