Nitrogen Mineralization from Citrus Tree Residues under Different Production Conditions
- H. Dou,
- A. K. Alva and
- B. R. Khakural
Under most citrus production conditions, dry leaves and other vegetative parts are returned to the soil under the trees. These materials and fibrous roots decompose on a regular basis. The objective here was to measure annual N contribution to citrus trees from organic residue decomposition. Mineralization of N was measured during 2 yr under citrus trees of two age groups each on Tavares fine sand (hyperthermic, uncoated Typic Quartzipsamment) and Wabasso sand (sandy, siliceous, hyperthermic Alfic Haplaquod). Mineralization of N from tree residues under the canopy accounted for 58 to 84 and 126 to 153 kg N ha−1 yr−1 for the 4- and 20-yr-old trees, respectively, on the Tavares fine sand and 39 to 64 and 121 to 126 kg N ha−1 yr−1 for the 7- and 40-yr-old trees, respectively, on the Wabasso sand. The transformation of potentially mineralizable N (i.e., total N in dry crop residue and fibrous roots under the canopy) into inorganic forms (i.e., percentage mineralization) was greater in Wabasso sand (41–86%) compared with that in Tavares fine sand (17–71%). Significant correlations (r = 0.82 [significant at P = 0.05] and 0.84 [significant at P = 0.01]) were found between measured quantities of mineralized N and potentially mineralizable N. There were also significant correlations between mineralized N and either rainfall or average temperature during each incubation interval. This study demonstrated that the quantity of net N mineralized from organic residues under the tree accounts for a significant portion of annual N requirement.
Copyright © .