Denitrification in agricultural soils: Summarizing published data and estimating global annual rates

Information taken from 336 measurements of denitrification in agricultural soils was summarized to assess the influence on denitrification of several factors related to soil, climate, agricultural management and the measurement techniques. The data set is summarized by calculating means and medians and balanced median values (with correction for unbalanced features) for all factor classes in the data set, and by developing a summary model to calculate global denitrification rates for a 0.5 by 0.5 degree resolution. Our results suggest that agricultural fields with high nitrogen application rates and poor soil drainage show higher denitrification values than those with lower nitrogen application rate and good soil drainage. The data also indicate that conditions in wetland rice systems are more prone to denitrification than those in upland cropping and grassland systems. Large uncertainties in the results are caused by differences between the measurement techniques and lack of long-term measurements covering the range of environmental and management conditions found in global agricultural fields.