Methane emission from rice-wheat cropping system in the Indo-Gangetic plain in relation to irrigation, farmyard manure and dicyandiamide application

Methane (CH4) is one of the important greenhouse gases accounting for 15% of the total enhanced greenhouse effect. Rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system is the most dominating cropping system in the Indo-Gangetic plains (IGPs) of India occupying 10.5 million ha of productive land could be a major source of atmospheric CH4. Effect of irrigation, urea, farmyard manure (FYM), and dicyandiamide (DCD) on emission of CH4 from an alluvial soil (Ustochrept) in rice-wheat cropping system was studied using the closed chamber technique. Total emission of CH4 from the rice-wheat systems ranged from 16.2 kg ha(-1) in the control treatment to 36.5 kg ha-1 in urea plus FYM treatment with an average emission of 20.8 kg CH4 ha(-1). Continuously saturated soil in rice gave higher CH4 emission compared to intermittent wetting and drying soil condition but the yields were lowered. Application of DCD with urea reduced emission of CH4 in rice-wheat system to 70%, while substituting 50% of inorganic N with FYM increased emission to 172% compared to application of entire amount of N through urea. In wheat negative fluxes of CH4 up to 0.1 kg ha(-1) per day was recorded. There was no difference in CH4 flux in wheat between the various irrigation treatments. In the most common fertilizer practice in IGPs the emission of CH4 is 21.2 kg ha(-1). Intermittent wetting and drying of soil in rice has a potential to reduce the emission. (C) 2003 Elsevier Science B.V. All rights reserved.