Cover crop, Centrosema spp., N-fixation, phosphorous, potassium

Abstract

The effect of phosphorous (80kg P ha^-1; P_80) or potassium (70 Kg K ha^-1; K_70) alone or in combination (P_80K_70) an growth, nitrogen (N) status and nodulation of Centrosema macrocarpum and Centrosema acutifolium were investigated in a pot experiment. Species wise C. macrocarpum as compared to C.acutifolium not only gave higher shoot, root and total plant dry matter (DM) yield, but also had a DM yield response to fertilizer applications consistently. Although the former compared to the latter species was lower in plant N concentration due to a dilution effect as a result of higher dry matter yield, the total plant N yield was also higher. N status of C.macrocarpum also improved more than that of C.acutifolium in response to fertilizer applications. With all fertilizer levels, C.macrocarpum had higher nodule numbers with significantly higher overall harvest mean. Comparing the different fertilizer effects, P_80 was clearly and consistently superior to K_70 in all parameters tested except in N concentration which was diluted due to the higher dry matter yield with P_80. Comparing between P_80 nd P_80K_70, the latter was
higher only in total DM yield while P_80 was superior in total plant N concentration and nodule numbers indicating the significance of P over K. It can be concluded that C.macrocarpum was the better species and considering the economic aspects as well, P_80 seems to be the best fertilizer.