Biomass production of green ganure crops and mineralization of organic nitrogen in coconut basins

Abstract

An investigation on biomass accumulation of green manure crops and mineralization of organic nitrogen in coconut basins was conducted at the College of Horticulture, Vellanikkara during 1993-94. The experiment was aimed at evaluating the performance of various green manures and cover crops grown in coconut basins based on their biomass accumulation, nutrient accretion and nitrogen dynamics in the soil after incorporation. The mineralization pattern of green manure in red and laterite soils was studied in a laboratory incubation study using 15N labelled green manure. The salient results of the investigation are abstracted below. Crotolaria striata which represented the neglected green manures and pueraria phaseoloides which represented the cover crops produces the maximum dry matter in coconut basins. The popular green manure Crotolaria junecea failed to grew and put forth good biomass accumulation under coconut. The highest N content was found to be with Pueraria. Cassia tora was found to be the richest source of P. The maximum K content was reported in Cassia tora and Sesbania aculeata. Pueraria phaseoloides and Crotolaria striata released the maximum quality of nitrogen to the soil. The ammonium-N accumulation was found to be high in the upper layer of 0 to 15 cm soil when compared to the 0 to 30 cm soil layer. Crotolaria striata and Pueraria released the highest amounts of ammonium-N. In the release of nitrate-N, Pueraria was found to be the most efficient closely followed by Crotolaria striata. In the case of total mineral N (ammonium+nitrate) content the highest quantity was extracted with Crotolaria striata followed by Pueraria. In the incubation experiment to study the pattern of mineralization green manure N, the N release in terms of 15NH4 extracted during different periods of incubation was the highest for Crotolaria striata followed by Sesbania aculeata. The mineralization of green manure 15N took place at a lower rate in laterite soil when compared to red soil.