Unravelling the Mechanisms of Improving Wheat Growth, Yield, and Grain Quality Under Long-Term Corn Straw Return plus N Fertilizer Mode

In modern agricultural production, straw return (SR) plus nitrogen (N) fertilizer (SR-N) input has been considered a better practical mode to improve soil fertility and crop yield. Here, we investigate the underlying mechanisms of long-term SR-N application on wheat growth, yield, and quality. Wheat seeds were cultivated in 11-year-old plots treated with different N fertilizer levels under corn SR and non-straw return (NSR) conditions. Five levels of N fertilizer were set: N0 (0), N1 (90 kg ha(-1)), N2 (180 kg ha(-1)), N3 (270 kg ha(-1)), and N4 (360 kg ha(-1)). The wheat plants in SR-N2 exhibited the best growth status, the highest yield, and yield components. Physiological indicators exhibited that wheat plants in SR-N2 also had the maximum chlorophyll, soluble sugars, and protein contents, the highest antioxidant enzyme activities, and the lowest malondialdehyde (MDA) content. Wheat grains in SR-N2 had the highest protein content, which might be attributed to the highest glutamine synthetase activity during filling stage. qRT-PCR analysis showed that six genes related to N uptake and assimilation were significantly upregulated in SR-N2 treatment. Taken together, SR-N2 might be the effective mode that decrease the N fertilizer usage but maintain the maximize crop yield and grain quality by reducing oxidative stress and upregulating the expression of N metabolism-related genes.

Automated summary

The study suggests that long-term straw return combined with nitrogen fertilizer application has a positive impact on wheat yield and quality, especially at the N2 level where wheat plants exhibit optimal growth status, highest yield and yield components, lowest oxidative stress, and highest protein content.