Objectives In response to the unclear regulation of the components of maize grain nutritional quality during the grain filling period by soil fertility, the accumulation of maize grain nutrients, yield and its response to soil fertility level were studied to provide a theoretical basis for high-yield, efficient, and green cultivation of maize.

Methods Based on a tillage method positioning experiment started in 2018, the soil nutrient contents of various tillage method treatment plots (a total of 9 treatments, 27 plots) were analyzed in 2020−2021, the comprehensive fertility value was calculated, and the soils of all plots under treatment were clustered into high, medium, and low groups. At 20, 40, 60 days after maize anthesis (physiological maturity), the total starch, crude protein, and crude fat contents in the kernels were analyzed, and the maize yield and yield components were investigated at maturity. The impact of different soil fertility levels on the nutritional quality components and yield of maize kernels after anthesis (during the grain filling process) was analyzed.

Results Straw incorporation with subsoiling and straw incorporation with deep tillage were at a high soil fertility level in two years. In 2020, the tillage methods under low soil fertility level included no-tillage, deep spin in strip cultivation, shallow rotary tillage, and the tillage methods under medium soil fertility level were subsoiling, deep tillage, straw incorporation with no-tillage, straw incorporation with strip cultivation. In 2021, the tillage method at the low soil fertility level was only shallow rotary tillage, and the rest of the tillage methods were at the medium soil fertility level. The differences of crude protein and crude fat content in grains was the largest at 40 to 60 days after anthesis, the difference of total starch content was the largest at 20 days after anthesis, and the difference of total soluble sugar content was the largest at 20 to 40 days after anthesis. Compared with low soil fertility, under high soil fertility, the decrease in grain crude protein content and the increase in grain crude fat at 40 to 60 days after anthesis in two years significantly increased by 29.85%−34.64% and significantly decreased by 28.07%−54.01%, respectively. The increment of grain total starch contents at 20 days after anthesis significantly increased by 5.98%−8.95%, and the decrease in grain total soluble sugar content at 20 to 40 days days after anthesis significantly increased by 14.63%−25.34% in two years. The enhancement of soil fertility could significantly alter the nutrient content of maize kernels at physiological maturity. Compared with low soil fertility, the total starch content of grains at physiological maturity increased by 1.44%–2.43%, the crude fat content of grains increased by 3.81%–4.10%, the total soluble sugar content of grains decreased by 12.48%–18.55%, and the 100-grain weight significantly increased by 1.87%–2.97% under high soil fertility. Increasing soil fertility significantly increased maize yield by affecting hundred-grain weight, with a yield increase of 6.55%−9.39% under high soil fertility compared to low soil fertility.

Conclusions The application of suitable cultivation methods can significantly improve soil fertility levels, with the best effects achieved by straw incorporation with subsoiling and straw incorporation with deep tillage. Improvement of soil fertility can affect the accumulation and conversion of various nutrients during the maize kernel filling stage, thereby regulating the content of various nutrient content components at physiological maturity. Compared to low soil fertility, high soil fertility enhances the accumulation of total starch and crude fat in maize kernels during the grain filling stage, thereby increasing the content of crude fat and total starch in kernels at physiological maturity, and also significantly increasing the hundred-grain weight and yield of maize.