Produção de forragem e remoção de nutrientes por dois híbridos de sorgo forrageiro, cultivados em Rio Largo - AL

Abstract

The nutritional status, concentration and accumulation of nutrients in the aerial biomass of forage sorghums BRS658 and Volumax were evaluated at the Engineering and Agricultural Sciences Campus of the Federal University of Alagoas, located in Rio Largo, in three cycles (first cut, and first and second regrowth). The study was installed in soil with good fertility, without exchangeable aluminum in the 0 to 40 cm profile. The experimental design was randomized blocks, with six replications. The chemical fertilizer used in sowing was equivalent to 70 kg of phosphorus, with 200 kg of N and 200 kg of K being applied in top dressing. In the first and second regrowth, only N and K were applied, also in doses of 200 kg per hectare, for both nutrients. In the first regrowth there was additional supervision, and in the second regrowth the supervision was complete, with rain and integrity totaling around 500 mm of water in each regrowth. During the panicle emission phase, leaves were collected in the three central rows to evaluate the nutritional status of the plants. When the sorghum plants had an average dry matter content close to 330 g kg-1, the sorghums were cut approximately 10 cm above the ground, subsequently determining the accumulation of dry matter and nutrients in the aboveground biomass. In the three cycles, plants contain adequate leaf concentration of macro and micronutrients, due to soil fertility and chemical fertilizers. In the three cycles, the concentration of crude protein in the aerial biomass varied from 79.68 to 81.88 g per kg of dry matter,sufficient for good ruminal fermentation. The agricultural practices adopted allowed high forage productivity, totaling around 42.0 t of dry matter per hectare in the three cycles. In intensive forage production systems, similar to the present study, nutrient removal is high, so we obtained average removal values of 541, 91 and 593 kg of N, P and K, respectively, per hectare, in the three cuts.

Keywords: Forage farming, Dairy farming, Nutritional efficiency, Protein.