Suitable chemical fertilizer reduction mitigates the water footprint of maize production: evidence from Northeast China.

Long-term excessive use of chemical fertilizer has led to water environmental degradation. Reducing chemical fertilizer use in crop production has become a consensus, and the effects of chemical fertilizer reduction on yield, water consumption and water environment urgently need to be explored. A field experiment including four fertilization treatments: normal fertilizer application (NFA), 15%, 30% and 45% fertilizer reduction (FR) was conducted and the water footprint (WF) was used as an indicator to explore how the chemical fertilizer reduction affected the maize WF. The results showed that the blue, green and total WFs of maize in the 45% FR and NFA treatments were larger than those in the 30% FR and 15% FR treatments in 2018 and 2019. The grey WFs of maize in the NFA treatment were the highest in 2018 and 2019, exhibiting a trend that the grey WFs in the NFA treatment >15% FR treatment >30% FR treatment >45% FR treatment in 2018 and those in the NFA treatment >45% FR treatment >30% FR treatment >15% FR treatment in 2019. The optimal treatment was the 15-30% FR compared with the current fertilization, in which the total WF of maize can be minimized and the maize yield can be maximized at the same time. Precipitation had a wide-ranging impact on the yield and WF of maize, especially the amount, intensity and interval of rainfall, which had an evident impact on the grey WF. This study is expected to provide a data foundation for reducing chemical fertilizer and improving water and fertilizer use efficiency in maize production.