Combined Application of Lime and a Nitrification Inhibitor (3,4-Dimethylpyrazole Phosphate) Markedly Decreased Nitrous Oxide Emissions from an Acid Soil

High nitrous oxide (N2O) emissions (2-10% of fertiliser N) were observed previously from acid soils cropped with sugarcane (Saccharum officinarum) in Australia. We assessed the impact of lime, a nitrification inhibitor (NI, as 3,4-dimethylpyrazole phosphate, DMPP), and copper (Cu) on N2O emissions from an acid sugarcane soil in a laboratory experiment using (1) urea (U), (2) U + DMPP, (3) U + CuSO4 center dot 5H(2)O (U + Cu), and (4) U + DMPP + Cu. The treatments were applied to both an un-limed soil (pH 5.1) and a limed soil (pH 6.9) and incubated at 25 degrees C and 55% water holding capacity (WHC) for 28 d, and then increased to 90% WHC for another 8 d to favour denitrification. At 55% WHC, both the addition of the NI (U + DMPP) and the liming of the acid soil significantly decreased cumulative N2O emissions, due to significantly lower net nitrifications. Liming and DMPP decreased N2O emissions by 79% and 90%, respectively. However, where lime and DMPP were applied together, N2O emissions decreased by 94% compared to those in the un-limed (acid) U-treated soil. In contrast, the addition of Cu and the increase in water content to 90% WHC had no significant effect on N2O emissions. Therefore, the combined use of lime and DMPP provides the best option to decrease N2O emissions from the acid soil.

Automated summary

The combined use of lime and nitrification inhibitor (DMPP) was found to be effective in reducing N2O emissions from acid sugarcane soil.