Mineralization Dynamics of Nitrogen and Phosphorus in Areca Catechu L.-Based Traditional Agroforestry System

Areca catechu L.-based agroforestry system is practiced by local farmers in which a variety of crops are cultivated along with trees to maximize harvest security. Most farmers do not use inorganic fertilizers to improve crop yields, mainly because they cannot afford to purchase these fertilizers, and for this reason cycling of nutrients through the decomposition of plant residues becomes an important phenomenon in this type of agroforestry system. In this context, a study was carried out to estimate in situ nitrogen (N) and phosphorus (P) mineralization as influenced by soil type and management system. Net N and P mineralization rates were studied on the basis of final concentrations of ammonia, nitrate, and P in soil using a buried-bag technique for one cropping cycle to examine temporal and depth variations across the three different sites (Harmutty, Nirjuli, and Doimukh). A significant variation in N mineralization was recorded among the three sites. Seasonal changes in N and P mineralization were also observed. The Harmutty site had highest rates of N mineralization during the rainy season and immobilization during spring. Phosphorus mineralization rate was higher during autumn at Doimukh and during winter in Harmutty and Nirjuli sites, whereas greater immobilization was recorded during the rainy season. The Harmutty site recorded a greater ammonification rate during September and immobilization during November and March months, the Nirjuli site recorded maximum ammonification during January and immobilization during November and March, and the Doimukh site had greater immobilization during March and ammonification during January. Nutrient dynamics may prove productive if managed properly in synchronization with mineralization that could result in fairly good crop productivity.