What are the key factors affecting maize yield response to and agronomic efficiency of phosphorus fertilizer in China?

Excessive phosphorus (P) fertilization in intensive agricultural areas in China has caused resource waste and serious environmental problems, resulting in a need to evaluate P use efficiency to develop reasonable, sustainable P use strategies. This study summarizes the yield response to P (YRP) and the agronomic efficiency of P (AEP) in maize (Zea mays L.) in the primary maize-producing regions of China. We collated data from 7025 field experiments performed between 2005 and 2010 in these regions to quantify the effects of different soil properties (soil type, pH, Olsen-P, organic matter, Ava-N, and Ava-K) and management practices (variety and planting system) on the YRP and AEP and to clarify their relative importance to the YRP and AEP. The average P fertilizer application rate, YRP and AEP of maize in China were 92.3 kg ha−1, 16.58 % and 12.69 kg kg−1, respectively. The YRP and AEP of maize in red soil were significantly lower than those in other soil types. In addition, the YRP and AEP of maize increased with increasing soil pH. At soil Olsen-P levels below 15 mg kg−1, the YRP and AEP decreased with increasing soil Olsen-P; however, the YRP and AEP remained relatively stable at higher soil Olsen-P levels. The YRP and AEP of ‘Haiyu 6’ and ‘Xianyu 335’ were higher than those of other maize varieties. Among the different planting systems, spring maize with irrigation achieved the highest YRP and AEP (23.52 % and 14.37 kg kg−1, respectively). In addition, random forest analysis indicated that the maize variety should be prioritized over soil fertility indicators and P application rates when integrated P management strategies are formulated for maize. It was suggested that YRP and AEP can be improved by altering such soil properties and management practices, furthermore, variety is the most important factor affecting YRP and AEP in maize production systems in China.