N availability, soil microbial biomass and β-glucosidase activity as influenced by the decomposition of nine plant residues during soil fertility improvement in Ghana

This study wasconducted to determine how the litter quality and decomposition of nine species (Acacia auriculiformis, Albizia zygia, Azadiractha indica,Baphia nitida, Gliricidia sepium, Leucaena leucocephala, Tithonia diversifolia, Senna spectabilis and Zea mays) influence soil N availability, microbial biomass and β-glucosidase activity during soil fertility improvement. The results on plant residue chemistry showed significant differences among species with N concentration ranging from 12.2 g kg−1 in Z. mays to 39.2 g kg−1 in B. nitida.C/N ratio was greatest in Z. mays (34.4) while lignin and polyphenol concentrations were greatest in A. auriculiformis. The highest decomposition rate (0.251% day−1) occurred in T. diversifolia and least in A. auriculiformis, A. zygia, B. nitida and Z. mays with half-lives of between 28 – 56 days. Similar to the results on decomposition, between 80 to 89% of N, P, K, Ca and Mg were released from T. diversifolia within 7 days compared with more than 70% retention in A. auriculiformis, B. nitida and Z. mays. Moreover, the half-lives of decomposition and nutrient release of G. sepium, L. leucocephala, A. indica and S. spectabiliswere within 14 days. Mineral N, soil microbial biomass and β-glucosidase activities increased in all treatments with T. diversifolia recording the greatest effect. While N mineralization occurred in all species throughout the experiment, an initial N immobilization was recorded in A. zygia, B. nitida, A. auriculiformis and Z. mays treatments for up to 14 days. Further, the results showed the decomposition, nutrient release rates, mineral N, soil microbial biomass and β-glucosidase activities were dependent on litter quality. Phosphorus, lignin, lignin/N ratio and (lignin + polyphenol)/N ratio were most influential based on significant (p = 0.05) results