Effects of composted swine manure on nutrient content in grains of Panicum miliaceum L.

Abstract

The aim of this work was to evaluate the effect of different doses of composted swine manure on protein and macronutrient contents of proso millet grains and in nutrient export by the crop. The experiment was carried out in the years 2013 and 2014 in a randomized block design, with four replications and five treatments, composed of four doses of composted swine manure (0, 4.0, 8.0 and 12.0 Mg ha1) and one dose of mineral fertilization (NPK 100-60-40 kg ha1). Compost and mineral fertilizers were applied manually in each plot after the sowing of the crop, according to the established doses. After the harvesting, grain samples were taken to determine protein, N, P, K, Ca, Mg and S contents, as well as the amount of macronutrients exported by the crop. The data were submitted to analysis of variance. The means of the variables related to the compost doses were compared to the control plot (absence of fertilization) and to the mineral fertilization plot using the Tukey’ test (P≤0.05), and the effects of CSM doses were assessed by regression analysis, adopting as selection criteria the model and the magnitude of the regression coefficients at 5% of significance. The export of nutrients from the field by P. miliaceum grains at the dose of 4.0 Mg ha-1 of compost was equal to the mineral fertilization recommended for the crop, justifying the use of swine manure as a substitute for mineral fertilization. The use of compost provides protein content in P. miliaceum grains similar to the use of mineral fertilizer.