ISSN 2375-1134
African Journal of Agriculture ISSN 2375-1134 Vol. 9 (4), pp. 001-007, April, 2022. © International Scholars Journals
Full Length Research Paper
Decomposition and nitrogen release by green manure legume residues in different soil types
Jude J. O. Odhiambo
University of Venda, Department of Soil Science, Private Bag X5050, Thohoyandou, 0950, South Africa. E-mail: [email protected]. Tel: +27 15 962 8431. Fax: +27 15 962 4749/8598.
Accepted 19 November, 2021
Abstract
A laboratory incubation experiment was conducted over a 16-week period to determine decomposition and N release by three green manure legume species, Mucuna (Mucuna pruriens), Lablab (Lablab purpureus cv. Rongai) and Sunhemp (Crotalaria juncea), in three soil types from South Africa. The amount of N mineralized from the residues was determined at 2, 4, 8 and 16 weeks from the onset of incubation. Nitrogen release pattern of the three legume residues followed a similar pattern in all the three soils, with sunhemp treated soil having the highest amount of mineral N after 16 weeks of incubation in all the three soils, followed by lablab and then mucuna. The amount of mineral N ranged from 121 to170, 96 to 134 and 92 to 108 mg kg-1 in the sunhemp, lablab and mucuna treated soils, respectively. The cumulative amounts of N from the legume residues mineralized recovered as mineral N in soil after 16 weeks of incubation ranged from 21 - 41% (92 - 121 mg kg-1), 30 - 68% (108 - 170 mg kg-1) and 26 - 60% (93 - 147 mg kg-1) of the initial added N contained in the residues in the soils with 62, 20 and 12% clay contents, respectively. Less than 50% of the initial added N was mineralized in the high clay content soil. Mineralization rate constant, k, was significantly correlated to the residue N content, net mineralized N, C/N ratio and Lignin/N ratio. Results from this study indicated that all the three legumes could contribute significant amounts of N for uptake by plants, with sunhemp tending to release N at a faster rate, followed by lablab and then mucuna. High clay content in soil slowed down N mineralization.
Key words: Green manure legumes, incubation, decomposition, N release, soil type.