Crescimento e composição química das braquiárias brizantha e decumbens, usadas como plantas forrageiras ou de cobertura de solo, na região de Coruripe -AL

Abstract

Brachiaria (Urochloa spp.) has been widely used in livestock and Brazilian agriculture, as forage and soil cover plants. Thus, the objective of the present study was to evaluate the dry matter accumulation rates and bromatological quality of brachiarias brizantha and decumbens in the edaphoclimatic environment of Coruripe. The soil used was a dystrophic Red-Yellow Latosol, of medium texture, with base saturation of 47% in the layer from 0 to 20 cm, medium phosphorus and high potassium content. Brachiaria sowing was carried out in April, in a randomized block experimental design, with five replications. The chemical fertilizers carried out were in doses equivalent to 150 kg, 50 kg, 150 kg of N, P and K per hectare. Evaluations of production and bromatological quality of brachiaria were carried out 45 and 60 days after plant emergence (D.A.E). For dry matter accumulation rates, the assessments were at 30, 45, 60, 75, 90 and 105 D.A.E. The brachiaria brizantha and decumbens had a high growth rate, but in the evaluations carried out at 45 and 60 D.A.E, the brachiaria decumbens had an accumulation of dry matter in the entire aerial part around 25% greater than the brachiaria brizantha. Regarding the concentration of nutrients in the entire aerial biomass, the brachiarias had the same concentration of crude protein, phosphorus and magnesium. For calcium, the levels in the aerial part of Brachiaria brizantha were higher than those of Brachiaria decumbens, with the opposite occurring in terms of sulfur concentration. When evaluated as soil cover plants and nutrient recyclers, brachiarias brizantha and decumbens had high productivity in the edaphoclimatic environment of Coruripe. At 105 A.D.E. the accumulation of dry matter by Brachiaria brizantha was 22.75 t per hectare, exceeding the accumulation of Brachiaria decumbens by 126.4%, since the production of Brachiaria decumbens was 18.00 t of dry matter per hectare. The average accumulations of nitrogen and phosphorus were respectively 267 and 73 kg ha-1 for brachiaria brizantha, and 228 and 44 kg ha-1 for brachiaria decumbens. There was no difference between brachiarias in terms of potassium, calcium, magnesium and sulfur accumulation. Potassium was the nutrient that accumulated the most in the aerial part: 604 kg ha-1, therefore exceeding the average accumulation of nitrogen by 357 kg per hectare. The average values of calcium, magnesium and sulfur accumulation were 58, 44 and 34 kg ha-1, respectively. Under the edaphoclimatic conditions of the present study, both Brachiaria brizantha and Brachiaria decumbens were excellent forage plants, and had a large accumulation of dry matter, can be used as soil mulch, and recycle nutrients, especially potassium, in direct seeding systems . Keywords: Forage, Direct Seeding, Cover Plants, Dry Matter.