Competição por potássio entre gramíneas e leguminosas consorciadas, em função da capacidade de troca catiônica das raízes

Resumo

The influence of the cation exchange capacity of roots on the chemical composition of legumes and grasses grown together was studied in a greenhouse experiment. A 3x3x3 factorial completely randomized design with three repetitions was used with three grasses, three legumes and three levels of potassium application constituting the treatments. Grasses were Panicum maximum J: acq., Cenchrus ciliaris L. var. ‘Gayndah’, Melinis minutifiora Beauv. and legumes Centrosema pubescens Benth., Calopogonium mucunoides Desv. and perennial soybean Glycine withtii C.V. Cooper. Potassium was applied in solutions of 0, 120 and 240 ppm. Three plants of each legume species were planted with three of each grass in pots containing 2 kg of soil. Forty days after germination the aerial parts of the plants were harvested, legumes and grasses separated and analysis of potassium, calcium and magnesium contents carried out.

The results indicated that capim-gordura, with the highest cation exchange capacity among the grasses, was the least competitive for potassium. Centrosema, with the lowest cation exchange capacity among the legumes, retained the lowest proportion of potassium. In general, increase in doses of potassium applied to the soil increased contents of potassium in the aerial portion of all the species studied. On the other hand, contents of calcium and magnesium decreased.