Controlled-Release Urea Boosts Yields and Profits for Rice and Eggplant Production in Hubei, China

China is the world’s largest producer (and consumer) of rice and eggplant. In Hubei province in central China, they are important cash crops. Local farmers tend to use soluble fertilizers including urea and compound fertilizers, with nitrogen (N) frequently being over used, while phosphorus (P) and potassium (K) are usually under applied.

To help deal with the nutrients imbalance and potential problems of excessive N fertilizer use, such as groundwater and surface water contamination, eutrophication, ammonia loss and low N fertilizer use efficiency, the IPNI China program decided to organize a project. Conducted with the Wuhan Botanical Garden of the Chinese Academy of Agricultural Sciences, the aim was to show how polymer-coated controlled-release urea (CRU) could increase the production and profitability of rice and eggplant. The trials applied N 6% lower than the common practice for rice and 17% lower than currently used for eggplant. The amount of P and K was also adjusted according to soil test results.

In-field rice production trials showed that substituting the currently used amounts with the correct rates of either regular urea (RU) or CRU increased grain yield, farm profitability and nutrient recovery. The grain yield for each kg of N fertilizer added, known as the agronomic efficiency, increased from 18kg rice/kg fertilizer for current farmer practices to 29kg rice/kg fertilizer when using CRU. For eggplant, using balanced nutrition and RU increased yields by 8.2 t of fresh fruit/ha and profitability by US$4,000/ha compared with current farmer practices. When using CRU, yields increased by 10.2 t/ ha and profitability by $4,990/ha, while the agronomic efficiency also increased.

The project showed using CRU consistently improved both yield and profitability for rice and eggplant production in Hubei. With less N applied and remaining in the soil at the end of the growing season, using CRU also brought the added benefit of decreasing the potential for nutrients to be lost to the environment.

The use of balanced nutrition and controlled release urea (CRU), or a combination of regular urea (RU) and CRU resulted in the greatest rice yields, net profit, and return on investment compared with the unfertilized control.