Effects of Phosphorous and Potassium on the Growth and Nodulation of Centrosema spp.

Thakshal Seresinhe, K.K. Pathirana


The effect of phosphorous (80kg P ha^-1; P_80) or potassium (70 Kg K ha^-1; K_70) alone or in combination (P_80 K_70) on growth, nitrogen (N) status and nodulation of Centrosema
macrocarpum and Cemrosema 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 farmer 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 and 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.

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