Abstract
Controlled release urea (CRU) is considered to enhance crop yields while alleviating negative environmental problems caused by the hazardous gas emissions that are associated with high concentrations of ammonium (NH4+) and nitrate (NO3−) in black soils. Short-term effects of sulfur-coated urea (SCU) and polyurethane-coated urea (PCU), compared with conventional urea, on NO3− and NH4+ in black soils were studied through the buried bag experiment conducted in an artificial climate chamber. We also investigated nitrogen (N) release kinetics of CRU and correlations between the cumulative N release rate and concentrations of NO3− and NH4+. CRU can reduce concentrations of NO3− and NH4+, and PCU was more effective in maintaining lower soil NO3−/NH4+ ratios than SCU and U. Parabolic equation could describe the kinetics of NO3− and NH4+ treated with PCU. The Elovich equation could describe the kinetics of NO3− and NH4+ treated with SCU. The binary linear regression model was established to predict N release from PCU because of significant correlations between the cumulative N release rate and concentrations of NO3− and NH4+. These results provided a methodology and data support for characterizing and predicting the N release from PCU in black soils.
Highlights
Mollisols are known in other soil classification systems as “black soils” in China
The accumulation of NO3 − in the soil treated with polyurethane-coated urea (PCU) was significantly lower than that of U and sulfur-coated urea (SCU), which may be due to the fact that N release could be controlled by the polymer coating according to the crop demand
PCU was more effective in maintaining lower soil NO3 − /NH4 + ratios, indicating that nitrification was slower with PCU treatment, which meant PCU was more suitable for crop growth than SCU and U
Summary
There are four main major regions of Mollisols on a world-wide basis. Black soils in northeast China are universally known for their good natural fertility and are good for food production [2,3]. In the 10–15 years, the northeast region is expected to increase China’s grain production by 50% [4,5]. Their physical and chemical properties are far superior when compared with other soils [3,6]. An important synthetic fertilizer, is widely used all over the world as the main source of plant nutrition [11,12,13]. Conventional urea increases nitrogen (N) content, its efficiency is low because N is only partially absorbed and utilized by plants [13,14]
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