Effects of biochar and N-stabilizers on greenhouse gas emissions from a subtropical pasture field applied with organic and inorganic nitrogen fertilizers.

ABSTRACT

Pasturelands contribute significantly to the global CO2, CH4 and N2O emissions. These gas emissions are influenced by the amount and type of N-fertilizers applied and local climate. Recent studies showed potential of biochar and N-stabilizer compounds in minimizing CO2, CH4 and N2O emissions by regulating N-release from N-fertilizers. The present study was aimed at determining and comparing the effects of biochar and N-(n-butyl) thiophosphoric triamide + dicyandiamide (N-stabilizer) on CO2, N2O and CH4 emissions from a pasture fertilized with cattle manure or urea. The study was conducted during 2015 and 2016 in an established bermudagrass (Cynodon dactylon L. Pers.). Treatments consisted of combination of N-sources (manure, and urea) and two mitigation technologies [pine hardwood biochar (BC) and N-stabilizer] along with control. Emissions of GHGs were measured from each plot using static chamber systems. Both BC and N-stabilizer applications with manure applied to the hay field significantly decreased N2O emissions by 42% and 45%, respectively, in the year-2, and emission factors compared to manure only treatment. Addition of N-stabilizer to urea had significantly decreased N2O emissions compared to urea alone, while BC had statistically insignificant effect although numerically lowered N2O emissions in both the years. Application of manure to the soil resulted in significantly higher CO2 emissions in both years and CH4 emissions in 2016 compared to unfertilized soil. Urea application had significant effect on CO2 emissions in 2016, while no effect on CH4 emissions compared to control. Application of either biochar or N-stabilizer did not significantly affect CO2 and CH4 emissions.