Structural characteristics of elephant grass fertilized with organic composted waste from production and slaughter of small ruminants

This study aimed to evaluate the morphophysiological characteristics of irrigated Pennisetum purpureum cv. Cameroon subjected to doses of an organic compost from waste generated by production and slaughter of small ruminants. The experiment was carried out in a grassland, during four growth cycles of 60 days. The area is located in the Embrapa Caprinos e Ovinos unit, in Sobral - CE, Brazil. Treatments consisted of organic compost doses (0, 13.3, 26.6, 39.9, 53.2 and 79.8 Mg ha-1) plus a mineral fertilization (nitrogen and potassium) at doses equivalent to 720 and 900 kg ha-1 year-1, respectively. The experimental design was arranged in completely randomized blocks, totaling four blocks with seven treatments each, in a split plot scheme with repeated readings over time. The plots corresponded to seven doses of an organic compost and an additional treatment (mineral fertilizer), and subplots to four growth cycles. The variables analyzed were total herbage biomass (THB), canopy height (CH), tiller population density (TPD) and water use efficiency for green leaf biomass production (WUEGLB) and green stem biomass (WUEGSB). In the first cycle, TPD decreased linearly with increasing doses of the compost, with 47 tillers m2 at the dose of 79.8 Mg ha-1, while THB and WUEGLB variables behaved quadratically, with a maximum point of 23.53 Mg DM ha-1 cycle-1, and 16.33 kg DM mm-1 for the doses of 66.52 and 62.94 Mg ha-1 of the organic compost. We concluded plant structural characteristics and water use efficiency were responsive to applications of the organic compost, and we recommend the dose of 67.7 Mg ha-1.