Phosphorus and Potassium Release Pattern from Leucaena Leaves in Three Environments of Haiti

Abstract

In tropical ecosystems trees have the potential to supply nutrients essential to crops. Leucaena [Leucaena leucocephala (Lam) De Wit] leaf decomposition experiments were established at three sites in Haiti representing diverse soil types to assess the potential of leucaena leaves to supply P and K to crops and to determine their pattern of release. Mesh bags containing 17.4 g of air-dried leucaena leaves were placed in plots receiving 100 kg ha⁻¹ of N as ammonium sulfate and leucaena prunings as mulch with and without 60 kg ha⁻¹ of P and 40 kg ha⁻¹ of K fertilizers for each crop. One bag from each plot was retrieved periodically over a period of 32 weeks for ash free dry matter, P and K determination. In the three locations applications of P–K inorganic fertilizer had no significant effects on leucaena leaf ash free dry matter remaining, P and K concentration nor content of leaves. Cumulative leucaena leaf P content release after 32 weeks of decay for the three sites averaged 4.9 kg ha⁻¹. Cumulative leucaena leaf K content release for the three sites was about 35.4 kg ha⁻¹. The rate of K release was higher in very humid climate than in semi-humid climate. The pattern of leucaena leaf ash free dry matter remaining, residual P and K content followed a double exponential model of decomposition for the three locations. Leucaena leaves applied at the three sites showed potential to supply P and K to crops. Plant material quality, time of decomposition and tree age should be investigated in future studies.