Phosphorus accumulation characteristics and suitable phosphorus application rate of maize under full straw returning

Objectives The effects of phosphorus (P) accumulation characteristics and maize yield under long-term full straw return to the field were investigated. We aim to provide a theoretical basis for the appropriate rate of P fertilizer application under the condition of full straw returning.

Methods The experiment was conducted in Gongzhuling City and Chaoyangpo Town of Jilin Province from 2017 to 2019, using a two-factor design. The main factor was P level (P₂O₅) at 0 kg/hm² (P0), 45 kg/hm² (P45), 90 kg/hm² (P90), 135 kg/hm² (P135), and 180 kg/hm² (P180), respectively. The secondary factor was maize cultivar Fumin 985 and Xiangyu 211. Yield and its composition, and P absorption of different parts at flowering and maturity stages were determined.

Results Location, year, and P application levels significantly affected maize yield, panicle number, panicle grain number, and 100-grain weight. Further, the interaction of location, year, and phosphorus application affected maize yield, panicle number, panicle grain number, and 100-grain weight (P<0.01) . P90 had the highest yield, panicle number and 100-grain weight, which were increased by 14.4%, 6.15%, and 5.78% compared with P0. P accumulation ratio before anthesis increased at both sites from 2017 to 2019, compared with P0. P90 and Chaoyangpo recorded the highest P accumulation ratio. Under P90, P accumulation was increased by 24.5% and 15.5% in 2018 and 2019 than P0. Maize P absorption, especially the accumulation of straw, was relatively stable and less affected by P levels. However, P accumulation in maize grains increased at first and then decreased. Compared with P0, P absorption in grains at Gongzhuling under P90 and P135 increased by 22.3% and 14.6% (P<0.05) in 2017, respectively. From 2017 to 2019, the P absorption of grains in P90 at Chaoyangpo significantly increased by 7.03% to 12.5% (P<0.05). When the P application level was 90 kg/hm², translocation rate and quantity and contribution rate to grain reached the highest level. According to the quadratic equation of one variable, the maximum yield of Gongzhuling and Chaoyangpo were 12161 kg/hm² and 12435 kg/hm², respectively, and the optimal economic fertilizer application rate was 77.2 kg/hm² and 71.9 kg/hm², respectively. The optimal economic P application rate was 74.6 kg/hm² in the two experimental sites .

Conclusions When P₂O₅ application level was less than 90 kg/hm², increasing P application positively affected the P accumulation ratio before anthesis, P absorption in grain , translocation rate and quantity, and contribution rate to grain. Full straw return to the field could achieve a yield of 12 t/hm² at P₂O₅ application rate of 71.9 to 77.2 kg/hm².