Adubação orgânica e mineral na composição química e produção do milheto (Pennisetum glaucum) no semi-árido.

Abstract

Due to its high drought resistance and adaptation to low fertility soils, fast growth, and good biomass and seed production, pear millet (Pennisetum glaucum) is a promising agricultural alternative of the Brazilian Northeast semiarid region. With the objective to evaluate the effects of organic and mineral fertilization on pearl millet composition and production, an experiment was carried out in a Cromic Luvisoil, on the UFCG/CSTR/PB experimental station “NUPEARIDO”. The plots (total plot area = 13.44m2 , and net plot area = 8m2) were demarcated after weeding the experimental site. Then, macassar bean was sown in four experimental plots and incorporated in the soil as green manure 45 days later. The treatments consisted in control (no fertilization), NPK (25.2g.m-2 of ammonium sulphate, 22.2g.m-2 of simple superphosphate, .3g.m-2 of potassium chloride) or green (12.5 kg.m-2 of fresh macassar bean plant biomass), cattle (3.4kg.m-2) or goat (3.4kg.m-2) manure incorporated in the soil, with four replications totaling 20 plots in the whole experiment. Plant pacing (0.8mx0.4m) was similar in all plots. Data on plant height, internode length, tem diameter, and tiller and leaf number were collected at day 35 after germination. At day 60, millet plants were cut and data on fresh and dry biomass, number of panicles, fresh and dry panicle biomass, and 1000-seed, dry seed, dry cob, and dry caryopsis plus hilum biomass were collected. Also, chemical and bromatological analyses were carried out in samples collected from the millet aboveground biomass. The results showed that bovine and goat manure applied on the soil increased plant height, internode length, stem diameter, tiller and panicle number, fresh and dry aboveground biomass, fresh and dry panicle biomass, 1000-seed and seed biomass, dry cob and caryopses plus hilum biomass. Nitrogen content in millet aboveground biomass was higher in control plants, P content was higher in cattle and goat manure treated plants, and S content was positively affected by NPK and cattle and goat manure. Potasium, Ca and Mg contents in millet plants were practically not affected by treatments, especially B, Cu, Fe, Mn and Zn contents. Forage N, P, K, Ca, Mg, S, B, Cu and Fe accumulation tended to increase with cattle or goat manure application. Cattle or goat manure increased significantly Mn and Zn levels in forage. Bromatological analyses showed significant differences in crude protein and neutral detergent fiber contents, while no significant differences were observed in acid detergent fiber and ash contents. It is concluded that millet presented a high productivity in the semiarid region of Paraíba.