Greenhouse gases emissions and agronomic productivity as influenced by varying levels of N fertilizer and tank silt in degraded semiarid Alfisol of Southern India

Abstract

The study aimed to assess the effects of combined application of urea nitrogen (N) and tank* silt (TS) on greenhouse gases (GHG) emissions [i.e., carbon dioxide (CO2) and nitrous oxide (N2O)] and agronomic productivity of maize-horsegram system. A factorial [urea (0, 60, 120, and 180 kg N ha−1)] and tank silt (0 and 30 t ha−1) replicated thrice randomized block design was employed for this investigation. Results of the study showed that maize grain yield was significantly influenced by the sole application of both N fertilizer and TS. When both the N fertilizer and TS were combined, the grain yield was significantly (p < 0.01) improved by 5% (4870 kg ha−1) over the highest yield observed under only N. We have noticed a significant (p < 0.01) residual effect of N and TS on horsegram straw yield during all the years of experimentation. With the increase in N-rate, there was an increasing trend in CO2 emission noticed in all the years including the pooled year data. Compared to CO2 emission, N2O emission was greatly influenced by nutrient management and amendment application. Among the seasons, the post-rainy season (Rabi) had a slightly lower emission trend of CO2, during all the years as compared to the rainy season (Kharif). The observed results marked the marginal increasing trend of cumulative CO2 (cCO2) emissions with regard to increasing doses of urea. Tank silt addition slightly favoured a CO2 emissions. The trend of cumulative N2O (cN2O) emission was greatly influenced by the dose of urea following the order of N180 > N120 > N60 > N0. However, N fertilizer application influenced the cCO2 emissions (r = 0.83), and significantly increased the cN2O emission (r = 0.99). Therefore, optimum and timely application of urea combined with TS is recommended as an effective strategy to combat GHG-based emissions (specifically N2O based) in semiarid rainfed regions.