Doses de fósforo, épocas de coleta e o crescimento e diagnose nutricional nos capins braquiária e colonião

Abstract

Two experiments were carried out in nutrient solution, one with ‘signal’ grass (Brachiaria decumbens Stapf.) and another with ‘colonião’ grass (Panicum maximum Jacq. cv. Colonião) during spring and summer seasons. The experiments consisted of a 3 X 10 factorial, in a randomized complete block design, with three P rates (3.1, 15.5 and 31.0 mg L-1) and 10 harvest dates, with four replications. The results showed a significant (P<0.05) interaction between P rates and harvest dates with respect to dry matter yield and plant P concentration for the two grasses. Sedlings of ‘signal’ grass concentrated P in leaf tissue and P rates did not change plant dry matter or acid phosphatase activity in leaves. Nineteen days after transplanting, ‘signal’ grass yield was linearly related to P rates. Both plant dry matter and P concentration in young leaves of ‘colonião’ grass were related to increased P availability. A negative correlation was found between shoot yield and acid phosphatase activity for the two grasses.