Tenor of macro nutrients and dry matter productivity of covering crops in function of the potassium doses

With the adoption of the system of direct sowing it is necessary the formation of a straw layer in the surface of the soils. In this sense, some species of grass can be used for that goal, besides; those plants can act in the recycling for the accumulation of nutrients in the aerial part, and its readiness for the subsequent culture. The potassium is one of the most accumulated nutrients for many of those plants. The objective of this work was to quantify the macronutrients tenor and the productivity of dry matter of Penisetum glaucum L. and Panicum miliaceum L. under different potassium doses. A blocks at random design, with the treatments disposed in factorial 3x2, was used, being the factors: covering cultures (P.glaucum and P. miliaceum) and potassium doses (0; 50 and 100 kg ha-1 of K2 O), with four repetitions. The matter dries was evaluated and the tenors of N, P, K, Ca, Mg and S in them, at 50 days after sowing covering cultures. P.glaucum produced larger dry matter content and tenor of N, K and Mg in the aerial part, independently of the K dose applied, while the tenor of P decreased with the application of high dose of K in the soil. The application of K influenced on the tenors of Ca and S in the two covering cultures, nevertheless P.glaucum accumulated higher tenor of those macronutrients in the absence of application of K