Abstract

Litter mineralization is a crucial process in providing nutrients through decomposition to plants, which also depends in the biochemical composition of the litter and soil properties as well. Decomposition rate of Erythrina abyssinica and Erythrina brucei in Luvisol was investigated in relation to their nutrient release dynamics such as NH₄⁺-N and NO₃^--N in relation to their initial concentrations of lignin, acid detergent fiber, cellulose and total polyphenol content and their ratios. The dynamic was followed in an incubation pot experiment, complete randomized design in replication. E. abyssinica has an average of 4.05, 9.7 and 2.04% TN, lignin and total polyphenol content respectively. E. brucei has also an average of 3.05, 12.63 and 1.05% content of TN, lignin and total polyphenol respectively. The samples of E. abyssinica and E. brucei were ground and incorporated with Luvisol in pots. To determine the amount of ammonium and nitrate released each treatment and control were sampled and analyzed on weekly basses. The lignin and total polyphenol was significantly positively correlated with the release of NH₄⁺-N, while the NO₃^--N showed significant negative correlations with the release of ammonium. From the experiment, it was observed that the E. abyssinica with lower content of lignin and high in TN has released the nutrients faster whereas E. brucei with high lignin and low total polyphenol content released slowly.  In general, these leguminous trees released NH₄⁺-N and NO₃^--N easily because of their high total nitrogen content and low lignin, ADF, cellulose and total polyphenol content. They attained their half-life within 2-3 weeks. Therefore, E. abyssinica and E. brucei bears fast mineralization as a result they can be used for fast-term correction of crop nutrient demand. However, more detailed researches are needed to synchronize and verify laboratory results with field measurements of their effect on crop production and synchronization of soil nutrient availability and crop demand in different agro ecology and soil types.

Key words: Incubation, lignin, luvisol, total polyphenol, nitrate, ammonium.