Nitrous oxide production from soybean and maize under the influence of weedicides and zero tillage conservation agriculture

Current experiment envisages evaluating N₂O production from nitrification and denitrification under the influence of weedicides, cropping systems and conservation agriculture (CA). The weed control treatments were conventional hand weeding (no weedicide), pre emergence weedicide pendimethalin and post emergence weedicide imazethapyr for soybean, atrazine for maize. Experiment was laid out in randomized block design with three replicates. Soils were collected from different depths and incubated at different moisture holding capacity (MHC). N₂O production from nitrification varied from 2.77 to 6.04 ng N₂O g^-1 soil d^-1 and from denitrification varied from 0.05 to 1.34 ng N₂O g^-1 soil d^-1. Potential nitrification rate (0.16-0.39 mM NO₃ produced g^-1 soil d^-1) was higher than potential denitrification rate (0.45-0.93 mM NO₃ reduced g^-1 soil d^-1). N₂O production, nitrification, denitrification, and microbial gene abundance were higher in maize than soybean. Both N₂O production and nitrification decreased (p < 0.05) with soil depth, while denitrification increased (p < 0.05) with soil depth. Abundance of eubacteria and ammonia oxidizing bacteria (AOB) were high (p < 0.01) at upper soil layer and declined with depth. Abundance of ammonia oxidizing archaea (AOA) increased (p < 0.05) with soil depth. Study concludes that intensive use of weedicides in CA may stimulate N₂O production.