Controlled‐release urea improved cotton productivity and nitrogen use efficiency in China: A meta‐analysis

The use of controlled‐release urea (CRU) is recommended to improve crop productivity without compromising environmental quality, but the overall effects on cotton (Gossypium hirsutum L.) growth are not well studied. A meta‐analysis was conducted to evaluate the effectiveness and potential role of CRU in improving cotton productivity in China. The results indicated that CRU increased cotton yield by 9.8% and nitrogen use efficiency (NUE) by 19.4% relative to urea at equal N rates, although the increase in yield was not statistically significant. Cotton yield increases were greater in sandy‐textured soil than in loam or clay soil, and in experiments sustained for more than 2 yr than in experiments sustained for 1 yr. In addition, the increase in NUE with CRU was enhanced at medium (170 < N ≤ 220 kg N ha−1) and high N rates (>220 kg N ha−1), at high CRU blending ratios (≥70%) and in soils with pH >7.5. These results demonstrate that CRU should be more widely used for cotton production in China, especially in sandy‐textured soil with increased N application. Core Ideas Controlled‐release urea has the potential to improve cotton yield and nitrogen use efficiency. Yield increase with controlled‐release urea was greater in sandy soil with a longer conducted season. A decreased N rate is possible with controlled‐release urea to maintain cotton yield and reduce fertilizer use.