Mitigation of greenhouse gas intensity by supplementing with Azolla and moderating the dose of nitrogen fertilizer

Abstract

Integrated use of biological-chemical nitrogen application during rice cultivation is the way forward for sustainable rice production. Experiments were performed to evaluate the effects of Azolla (blue green algae) application along with reduced dose of recommended N fertilizer (urea) application on emissions of nitrous oxide (N2O), methane (CH4), global warming potential (GWP) and greenhouse gas intensity (GHGI) in rice. The study consisted of nine treatments on growing three rice cultivars Pusa 1509, Pusa RH-10, and Pusa-44 under recommended fertilizer (120 kg N ha−1 by Urea), reduced fertilizer along with Azolla application (90 kg N ha−1 by urea +50 g m−2 Azolla), and low fertilizer along with Azolla application (60 kg N ha−1 by urea +50 g m−2 Azolla). The lowest cumulative seasonal emissions of N2O, CH4, and GWP were observed in LN1509 (81.55 mg N2O m−2), RN1509 (2.476 g CH4 m−2), and RN1509 (110.0 g CO2 eq. m−2), respectively. Application of Azolla along with the reduced dose of urea did not significantly decrease the yield of rice and the GHGI reduced by 18.41%, 16.88%, and 17.97%, respectively, in Pusa 1509, Pusa RH-10, and Pusa-44 as compared to the recommended fertilizer treatment. The findings of this study suggested that the use of Azolla in rice might help in reducing the application of urea fertilizer by 25% in rice without affecting the rice yields. This will be a win-win situation for the farmer who will be saving on the cost of fertilizer and for the policy makers as well by mitigating the greenhouse gas emissions.