Humate-Coated Urea as a Tool to Decrease Nitrogen Losses in Soil
Processes of N transformation in soil as affected by application of the three kinds of urea fertilizers,conventional urea(U),humate-coated urea(U-HA),and urea treated with the urease inhibitor NBPT(U-UI),are examined in a model laboratory experiment.Effects of urea fertilizers on soil chemical(content of water-extractable N-NH4 and N-NO3),and microbiological properties(rate of actual and potential N2O emission,basal and substrate-induced respiration,microbial biomass C,emission of ethylene)are focused to answer the following questions:(i)whether humate-coated urea has the ability to decrease N losses in soil;and(ii)how it affects soil biological activity comparable to synthetic urease inhibitor.The results showed that U-HA demonstrated advantages comparable to U in its ability to decrease N losses in soil:it increased N-NH4 content by 35%,reduced nitrate content by 9%,and decreased N2O emissions by 50%.U-HA promoted basal soil respiration by 10%and the specific activity of the soil microbial community by 7%,providing the highest metabolic quotient qCO2.Comparably to NBPT-treated U,U-HA mainly shows intermediate results between U-UI and conventional U.Considering the low cost of raw humates,U-HA can be regarded as a promising tool to decrease N losses in soils.
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