Crop establishment and nitrogen management affect greenhouse gas emission and biological activity in tropical rice production

Abstract

The comprehensive impacts of different nitrogen management and crop establishment on greenhouse(GHG) fluxes are not well documented. GHG emissions from rice paddies under different nitrogen man-agement and crop establishment merit attention because nitrogen fertilizer is indiscriminately used forthe intensification of rice cultivation. Field trials were conducted to assess methane (CH4), nitrous oxide(N2O) and carbon dioxide (CO2) emissions, labile C pools, microbial population and enzymatic activitiesin rice soil under different crop establishment and nitrogen (N) management practices. The crop estab-lishment methods included aerobic rice (AR) that involved dry direct seeding under non puddled andnon-flooded situation and puddled transplanted rice (PTR) under flooded condition. Nitrogen manage-ment practices were control, 100 kg N ha−1as prilled urea (PU) and applied conventionally, 100 kg N ha−1as neem coated urea (NCU), applied conventionally, 100 kg N ha−1as PU, applied on the basis of cus-tomized leaf colour chart (CLCC) recommendation, 100 kg N ha−1as NCU, applied on the basis of CLCCrecommendation, 100 kg N ha−1as PU and farm yard manure (FYM) in 1:1 ratio, applied conventionally.Cumulative seasonal CH4emission was 73–75% less in AR as compared to PTR. But seasonal N2O and CO2emissions from soils were significantly higher in AR. Global warming potential of AR was comparativelyless than PTR but yield loss in AR caused greenhouse gas intensity (GHGI) of AR to be at par with that ofPTR. Inclusion of FYM along with PU reduced N2O emission and maintained significantly higher (P ≤ 0.05)microbial biomass carbon concentration, nitrifiers, Azotobacter and Azospirillum population and dehydro-genase, -glucosidase and urease activities in soils of AR and PTR. Real time N application according toleaf colour chart and use of slow release N fertilizers can reduce N2O emission, minimize yield loss andlower GHGI of AR.