Effects of phohorus, potassium and molybdenum in guinee-grass mixed with siratro

Abstract

This field experiment studied the effect of levels of P, K, and Mo in a mixed guineagrass plus siratro pasture. The experimental design was in Complete Randomized Block with two replications and the treatments were combined in a incomplete factorial using a modified central composite design. At seeding time it was used a diferential fertilization, applying only 20 kg of P₂0₅/ha in the rows of the grass and, in the rows of the legume the P, K and Mo fertilizations were according to the level combinations. The grass was also studied as single culture, fertilized with levels of N. In the mixture, the grass, the legume and the grass + legume yields were increased with the application of about 120 kg of P₂0₅/ha and 70 kg K/ha, being the response to Mo different for each component and equal to the application of 196, 274, and 225 g of molybdemum per ha. No limiting siratro productions occurred when the soil K was arround 60 ppm and the forrage K concentrations were 1,40% in the dry matter (65°C) which correspondend to an applicaction of 50 kg K₂O/ha harvest. Considering a four year mean the dry matter yield of the mixture was equivalent to a fertilization of 120 kg N/ha in the grass alone.