Impact of Tree Leaf Application on Microbial Biomass and Productivity in Tropical Dryland Rice Microcosm

Abstract

The present study shows the positive impact of application of tree leaves on soil microbial biomass and rice productivity. Chopped leaves of three nitrogen (N) rich tropical tree species, Dalbergia sissoo, Cassia fistula and Azadirachta indica alone and in combination with low quality wheat straw and chemical fertilizer alone were incorporated in soil to evaluate their effects on soil microbial biomass and biological productivity of rice crop under dryland conditions. D. sissoo, C. fistula and A. indica leaves had low lignin + polyphenol/N ratio (LIG + PPL/N, 4.5–12.4) as compared to combined treatments. Among tree leaf treatments, D. sissoo showed higher increase in mean microbial biomass C (195%) and N (242%) over control. In combination treatments, D. sissoo + wheat straw showed maximum microbial biomass C and N (242 and 25 μg g−1). The microbial biomass C and N remain low in fertilizer and wheat straw treatments. D. sissoo, C. fistula and A. indica leaf treatments showed about two times greater soil available-N as compared to control. In N rich species leaf treatments, total net productivity (TNP) was 68–161% greater than control whereas in combination and fertilizer treatments the increases were 23–48 and 14%, respectively. Among all treatments, application of D. sissoo, C. fistula and A. indica tree leaf alone showed substantially higher productivity than others. The addition of tree leaves caused comparable level of productivity, especially ANP, than in fertilizer alone treatment. Thus, direct application of N-rich tree species leaves that have low LIG + PPL/N ratio may serve as a short-term option for rapid enhancement of rice productivity and soil fertility.