LAUSR

Abstract Understanding the responses of the leaf area index (LAI) and photosynthetic rate to phosphorus (P) fertilization is important for optimizing P management and obtaining high grain yield for summer maize. A field experiment with six rates of P application (0, 12.5, 25, 50, 100, 200 kg ha−1) was conducted in a maize field in 2014 and 2015. P application significantly increased the soil Olsen-P concentration, and the critical level of soil Olsen-P concentration for maximal shoot P concentration was 20.5 mg kg−1. As the shoot P concentration increased to 2.01 g kg−1 in 2014 and 2.40 g kg−1 in 2015, the LAI and net photosynthetic rate got maximum but then plateaued at higher shoot P concentration. The highest grain yield (11.6 Mg ha−1) was attained when the critical LAI and net photosynthetic rate was 4.85 m2 m−2 and 28.5 μmol CO2 m−2 s−1, respectively. The length of barren ear tips was reduced by optimizing the P application rate then increased grain yield. By properly managing P fertilization, maize growers can maximize the LAI and net photosynthetic rate and thereby attain high grain yields without applying excessive P.