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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 + CuSO4.5H2O (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 °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. [ABSTRACT FROM AUTHOR]

Copper is an element necessary for the proper growth and development of plants, but when taken in excess amounts, it can be toxic. Its availability for plant can be reduced by using organic fertilizers or soil liming. The aim of the study was to investigate the effect of increasing doses of copper (100, 200, and 300 mg Cu·kg−1 of soil) application in combination with various organic amendments (cattle manure, chicken manure, and spent mushroom substrate) on the yield of cocksfoot and its content and uptake of this metal, and to determine its coefficient of bioaccumulation and tolerance indices. The toxic effect of copper manifested by significant decrease in the yield of the test plant was after the application of 300 mg·kg−1 of soil. Increasing doses of copper application increased its content and uptake by the test plant, while observing the decreasing bioaccumulation factor. All the soil amendments reduced the toxic effect of copper on cocksfoot. The most effective organic amendment in terms of yield and protective effects against high levels of copper was cattle manure, in the case of which the Org/Cu and Cu/Org tolerance indices were highest. [ABSTRACT FROM AUTHOR]