Influence of inorganic N on mycorrhizal activity, nodulation, and growth ofLeucaena leucocephalain an oxisol subjected to simulated erosion

The influence of inorganic N on the development of mycorrhizal symbiosis inLeucaena leucocephala(Lam.) de Wit was studied in an Oxisol subjected to simulated erosion. The plants were grown in pots containing soil samples inoculated with the VAM fungusGlomus aqgregatumand amended with 0, 25, 50 or 100 ppm N. The extent of VAM colonization of roots increased with increasing levels of N in both eroded and uneroded soils. However, the level of infection was significantly higher in the eroded soil than in the uneroded one. Mycorrhizal activity monitored in terms of P content of leucaena subleaflets increased significantly in the eroded soil when it was amended with 25 ppm N and became similar to that observed in the uneroded soil. Nodule dry matter production and shoot N concentration increased significantly with N application upto 50 ppm. Above this level of N, nodule dry weight declined while N concentration did not change. Application of 25 ppm N to the eroded soil also significantly increased shoot and root dry weights while no change was observed in the uneroded soil. A further increase in N level did not improve yield. The results illustraste the potential benefits of starter N in the establishment of mycorrhizal and nodulatedLeucaena leucocephalain eroded soils