Combining Organic Fertilizer With Controlled-Release Urea to Reduce Nitrogen Leaching and Promote Wheat Yields

Soil deterioration, low nitrogen use efficiency (NUE), and environmental risks caused by excessive chemical N fertilizer use are key factors restricting sustainable agriculture. It is extremely critical to develop effective N management strategies that consider both environmental and agronomic benefits. From 2017 to 2019, a field experiment was conducted to assess the effects of combinations of organic fertilizers (OF, provided at 30, 50, and 70% of the total applied N) and controlled-release urea (CU) on the NUE, N leaching and wheat yield compared with the effects of urea and CU. The results suggested that OF released N slowly in the early stage and showed a significant residual effect, while CU released N quickly in the first 2 months. The OF substitutes with 30-50% CU increased wheat yield by 4.2-9.2%, while the 70%OF+30%CU treatment showed no significant difference relative to the urea treatment. The average maximum apparent NUE recovery (50.4%) was achieved under the 50%OF+50%CU treatment, but the partial factor productivity was not affected by the N type. As the OF application rate increased, the total carbon content increased, and the total N value decreased. The $$ -N and $$ -N concentrations in the OF+CU treatments were lower before the jointing stage but higher from the grain-filling to mature stages than those in the urea treatment. $$ -N and $$ -N were mainly concentrated in the 0-60-cm layer soil by OF substitution, and N leaching to the 60-100-cm soil layer was significantly reduced. Hence, the results suggest that the combination of 30-50% OF with CU synchronizes absorption with availability due to a period of increased N availability in soils and proved to be the best strategy for simultaneously increasing wheat production and reducing N leaching.