Biomass, production, decomposition of and N release from root nodules in two Casuarina equisetifolia plantations in Sonbhadra, India.
Two Casuarina equisetifolia plantation stands of age 5 and 8 yr, located in dry tropical climate of the Vindhyan plateau have been studied in order to evaluate biomass of root nodules, their productivity and N release from them. Active and inactive nodule biomass showed an inverse relation with time. Peak nodule biomass ranged from 86.5 to 155.2 kg/ha in September-October and production varied from 92.9 to 170 kg/ha in 8-yr-old and 5-yr-old stands, resp. Relative decomposition rates for ash-free mass loss and N release were higher in the first 3 months (warm-rainy and transitional to winter) and decreased subsequently in the severe winter and summer seasons. N release was 7% more in the 8-yr-old than in the 5-yr-old stand. Patterns of mass loss and N release were similar in both stands but decomposition constant (k) was lower in the 8-yr-old stand. Multiple regression analyses showed that nodule, soil temp. and especially nodule C:N ratio were strongly correlated with nodule decomposition.