Objectives Replacing conventional urea with slow- and controlled-release urea (CRU) is an important strategy for balancing high crop yields and N₂O emissions in farmland. however, the relevant research results are not always consistent. We summarized the comprehensive effects of slow- and controlled-release urea on wheat yield and N₂O emissions, as well as the key influencing factors using Meta analysis. The purpose is to provide a theoretical basis for optimizing nitrogen application strategies for wheat across different ecological regions.

Methods Literature, published between 2005 to July 2024, was searched in CNKI and Web of Science Databases using key words such as controlled-release fertilizer, slow-release fertilizer, slow and controlled-release fertilizer, wheat, yield, N₂O, greenhouse gas. A total of 1458 papers were retrieved and screened using the following criteria: 1) inclusion of both CRU and common urea treatments; 2) reporting at least one wheat productivity index or N₂O emission; 3) Field experiments conducted in the mainland of China. Afer screening, 91 papers were selected, and 1311 pairs of data were extracted, including 535 for yield, 249 for nitrogen apparent use efficiency (NUE), 305 for nitrogen agronomic efficiency (NAE), 92 for biomass, 88 for production profit, and 42 for N₂O emission. The effects of CRU were analyzed under different climate, basic soil fertility, nitrogen application rate, and operation proportion.

Results In terms of the gross effect, replacing part of conventional urea with CRU significantly increased wheat yield (by 4.46%), NUE (by 12.20%), NAE (by 17.77%), and production profit (by 12.21%), while significantly reducing total field N₂O emissions (by −26.69%). However, CRU had no significant effect on above ground wheat biomass. Relative significance analysis revealed that nitrogen application rate, top dressing proportion, and soil total N content were the key factors influencing the CRU’s yield-enhancing effects. CRU performed better with higher top dressing proportions, reduced N fertilizer application rates and reduced soil total N content. Moreover, CRU showed higher yield effect when cumulative precipitation during the wheat growing season was <450 mm, planting density was ≤220 plants/m², and when applied to wheat cultivars other than weak gluten types. In addition, the yield increasing effect of CRU was more pronounced in soils with low clay content and organic matter less than 20 g/kg. Under various conditions, CRU significantly reduced total soil N₂O emissions compared to conventional nitrogen fertilizers, with particularly strong reduction when the CRU substitution proportion was >70%, soil organic matter content was >20 g/kg, and soil clay content was relatively high.

Conclusions  Partial replacement of conventional nitrogen fertilizer with CRU significantly increases nitrogen fertilizer utilization efficiency, wheat yield, and production profit while substantially reducing N₂O emissions in wheat fields. The effectiveness of CRU is closely related to climate conditions, wheat cultivar types, application rate and methods, and soil properties. CRU is strongly recommended in areas with low precipitation during the wheat growing season, for medium, mid-strong and strong-gluten wheat cultivars, and in sandy, loam, and clay loam soils. To optimize outcomes, total nitrogen application rates and planting densities should be reduced appropriately, and a high proportion of CRU and top dressing should be used to achieve both high wheat yields and reduced N₂O emissions in wheat fields.