Combined impact of reduced N fertilizer and green manure on wheat yield, nitrogen use efficiency and nitrous oxide (N2O) emissions reduction in Jharkhand, eastern India

Context

Increasing global demand for wheat necessitates heightened the nitrogen (N) input. However, this amplifies nitrous oxide (N₂O) emissions, impairing global climate change.

Objectives

To address this dual challenge of meeting crop demands while curbing N₂O emissions, a two-years (2022–2023) field study was carried out in Central University of Jharkhand, Brambe, Ranchi, Jharkhand, India. The study aimed to examine the impact of varying fertilizer during the wheat growing seasons on N₂O emissions, global warming potential (GWP) and nitrogen use efficiency (NUE).

Methods

Seven experimental treatments were set up in a randomized block design i.e., WF0, Control (no fertilizer), WF1 (N at recommended dose (RD), 150kgha⁻¹), WF2 (30 % reduce N at RD, 105kgha⁻¹), WF3 (Diammonium phosphate at RD), WF4 (Ammonium sulphate at RD), WF5 (Sesbania aculeata green manure, 5 t ha⁻¹ + 50 % reduce N, 75kgha⁻¹) and WF6 (Crotalaria juncea green manure, 5 t ha⁻¹ + 50 % reduce N, 75kgha⁻¹). The static chamber technique was used for collecting N₂O gas samples and concentration were analyzed through gas chromatography methods. Additionally, soil mineral nitrogen, enzyme activity, NUE and yield related parameters were analyzed.

Results

The results showed that the cumulative emissions of N₂O in WF3 increased significantly (p < 0.05) by 7.24 %, while those in WF5 and WF6 decreased by 39.90 % and 26.09 % respectively, compared to WF1. WF5 treatment significantly decreased GWP and greenhouse gas intensity of N₂O by 40 % and 59.71 % respectively, compared to WF1. In contrast, WF5 treatment significantly (p < 0.05) inhibited the nitrate reductase activity (NRA) and urease activity (UA). Along with reduced N₂O emissions, treatment WF5 also increased the NUE and wheat yield, by 61.98 % and 13.71 %, respectively, over the WF1 treatment. The correlation analysis found positive correlations between soil nitrate, ammonia, water filled pore spaces, NRA and UA, while NUE showed negative correlations with N₂O emissions.

Conclusions

Therefore, fertilization regimes, such as application of green manure i.e., Sesbania aculeata with 50 % reduction in fertilizer rate (75 kg N ha^–1) compared to the normal rate (150 kg N ha^–1), could be recommended as fertilization strategies to mitigate N₂O emissions and ensuring global food security.

Significance

The study outcomes provide indispensable insights for optimizing climate resilient agricultural strategies at regional and global scale. The data acquired from these regional analyses not only enrich national databases but also serve as pivotal inputs for refining the precision of the global emission budget.