Seed yield and quality responses of oilseed crops to simulated nitrogen deposition: A meta‐analysis of field studies.

Oilseed crops are widely planted and are closely associated with human nutrition and health. Globally, increased nitrogen (N) deposition has a significant impact on agricultural production; however, in‐depth knowledge of oilseed crop yields and quality is still lacking. Here, we performed a global meta‐analysis from 128 published papers with 462 paired observations to evaluate the response of oilseed crop yields, yield composition, protein, and oil content to simulated N deposition. The meta‐analysis showed that simulated N deposition significantly increased oilseed crop yields in a dose‐dependent and duration‐dependent manner. The yield compositions were also changed by N deposition, where pod numbers per plant (PNP) and seed weights per pod were significantly increased. Interestingly, our analysis identified PNP as the key factor determining the oilseed crop yield response to simulated N deposition. Additionally, the form of N deposition had no striking influence on either yields or yield components, whereas differences in the sensitivity in rape responses reflected differences in crop species. In terms of oilseed crop quality, although simulated N deposition increased the seed protein content in a dose‐dependent manner, there was a significant negative impact on the seed oil content. Furthermore, this negative correlation between seed oil content and biomass under simulated N deposition implies adverse effects caused by a dilution effect. Overall, our results suggest discrete responses of oilseed crop yield, seed protein and oil content to simulated N deposition. This study has ecological and biological implications for oilseed crop yield and quality responses facing global N deposition. [ABSTRACT FROM AUTHOR]