Effects of Plant Residue Decomposition on Soil N Availability, Microbial Biomass and β-Glucosidase Activity During Soil Fertility Improvement in Ghana

With limited use of inorganic fertilizers on smallholder farms, plant residues could be viable alternatives for soil fertility improvement. This study was conducted to determine how residue quality and decomposition of nine plant species influence soil N availability, microbial biomass, and beta-glucosidase activity during soil fertility improvement. Significant differences in N concentration were found among the species, ranging from 12.2 g kg(-1) in Zea mays to 39.2 g kg(-1) in Baphia nitida. The C/N ratio was the highest in Z. mays (34.4), whereas lignin and polyphenol concentrations were the greatest in Acacia auriculiformis. The highest decomposition rate (0.251% per day) occurred in Tithonia diversifolia, and the lowest in A. auriculiformis, Albizia zygia, B. nitida, and Z. mays, with the half-lives of 28-56 d. Between 80% and 89% of N, P, K, Ca, and Mg were released from T. diversifolia in 7 d, compared with over 70% retention in A. auriculiformis, B. nitida, and Z. mays. The decomposition and nutrient release half-lives of Gliricidia sepium, Leucaena leucocephala, Azadirachta indica, and Senna spectabilis were less than 14 d. Soil mineral N, microbial biomass, and beta-glucosidase activity increased under all treatments, with T. diversifolia having the greatest effect. While N mineralization occurred in all of the species throughout the experiment, an initial N immobilization was recorded in the A. zygia, B. nitida, A. auriculiformis, and Z. mays treatments for up to 14 d. Decomposition and nutrient release rates, mineral N, soil microbial biomass, and beta-glucosidase activity were dependent on residue quality, and P and lignin levels, the lignin/N ratio, and the (lignin + polyphenol)/N ratio had the most significant effects (P <= 0.05).