Uncovering the potentials of long-term straw return and nitrogen supply on subtropical maize (Zea mays L.) photosynthesis and grain yield

Abstract

ContextCrop straw is a significant byproduct of agricultural production and a rich source of nutrients, but it is carelessly disposed of, potentially harming the environment and wasting valuable resources. In China, returning straw to the soil as a means of disposing of agricultural waste is a crucial management technique that not only makes use of agricultural waste but also enhances soil quality and grain yield. ObjectiveA five-year (2018–2022) field experiment was designed to study the effect of straw treatment methods and optimal nitrogen (N) application rate on the photosynthesis process and grain yield of maize. MethodsThe different straw methods (straw return (SR) and traditional practice (TP) — no straw return) were assigned to main plots while the N levels such as N100 (100 kg ha−1), N150 (150 kg ha−1), N200 (200 kg ha−1), N250 (250 kg ha−1), and N300 (300 kg ha−1) were allotted to sub-plots. ResultsThe results showed the photosynthesis rate (Pn), intercellular carbon dioxide concentration, stomatal conductance, transpiration rate, relative chlorophyll content (SPAD), leaf area index (LAI), dry matter (DM), soil nitrogen content, maize grain nitrogen accumulation, and grain yield were increased with an increase in N levels. Similarly, SR also showed a promotion effect on the aforementioned parameters compared with TP. After five years, SR with an optimum N level (250 kg ha−1) increased the SPAD values (2%) and Pn (8%) which resulted in higher LAI (27%) compared with TPN300. As a result, more DM (15%) was formed and finally increased the grain yield (7%). It was revealed that the SPAD, Pn, LAI, DM, and grain yield were maximum at a higher 300 kg N ha−1 level but it was found statistically similar with 250 kg N ha−1. So in this study, SR with 250 kg N ha−1 is optimum for better photosynthetic efficiency, dry matter production, and grain yield. The correlation analysis also showed a positive correlation (i) of SPAD values with Pn (ii) LAI with SPAD values and Pn, (iii) DM with SPAD values, Pn, and LAI, and (iv) grain yield with DM under SR compared with TP. Conclusion and implicationIn summary, SRN250 resulted in better chlorophyll content and photosynthesis process that yielded more photosynthetic area for higher DM production and subsequently higher maize grain yield. The SR reduced the amount of N fertilizer and improved the grain yield and it is the best approach to improve grain yield and minimize agricultural waste production. Long-term trials are needed to understand the effects of straw incorporation and nitrogen application in different regions and locations.