The nitrogen supply capacity and application methods of straw-chemical mixed fertilizer in the sweet corn variety ‘Zhetian 19’

The global production of crop straw has been steadily increasing as the demand for crops continues to grow, with current output reaching approximately 4 billion tons annually. Crop straw is a nutrient-rich resource, but if not properly managed, it can pose environmental risks. Effective utilization of straw remains a significant challenge in agricultural production. To address environmental issues such as pollution from straw burning, soil degradation, low crop germination rates, and the increase in soil-borne diseases, this study adopts the "organic-inorganic granular fertilizer" method. By converting straw into granulated fertilizer and returning it to the field, this approach not only repurposes agricultural waste but also enhances soil quality and crop yields. A three-year field experiment (2020–2022) was conducted to investigate the effects of various application rates of SCMF (Straw Chemical Mixed Fertilizer) and optimal fertilization methods on the photosynthetic process, yield, soil nutrients, and sugar content of sweet corn. In 2020, SCMF and urea were applied to plots according to different fertilization methods and rates: S0, SUT0.5, SUT, SUB0.5, SUB, CK0, and CK. In 2021, based on the optimal fertilization rate identified in 2020, different fertilization methods were tested: SUT, SUB0.5UT0.5, SUB, CK0, and CK.In 2022, under the optimal fertilization method, SCMF application rates were adjusted according to a 10 % variation in nitrogen fertilizer content: S1.2UB, S1.1UB, SUB, S0.9UB, S0, CK0, and CK.Considering the chlorophyll content, leaf area index, dry matter accumulation, yield, soil nutrient status, and sugar concentration in sweet corn from 2020 to 2022, the SUB treatment demonstrated superior performance. Compared to CK (247.2 kg N ha⁻¹), the SUB treatment (229.2 kg N ha⁻¹) enhanced both the yield and quality of sweet corn, while SCMF applications led to an increase in sugar content. In 2022, the SUB treatment resulted in a 9.5 % increase in chlorophyll content, and the leaf area index at 10 days after planting (DAP) was the highest observed. This increase in leaf area index contributed to a higher accumulation of dry matter (6.3 %) and ultimately led to an 8.7 % increase in sweet corn yield and a 9.7 % increase in soluble sugar content. The findings suggest that the SUB fertilization rate and method are optimal for achieving higher chlorophyll content, leaf area index, yield, and soluble sugar concentration in sweet corn. Additionally, soil nutrient analyses indicated that SCMF applications improved soil pH, total nitrogen, and organic matter content.Therefore, the SUB treatment resulted in increased chlorophyll content and leaf area index, enhancing photosynthetic efficiency and providing a larger area for dry matter accumulation and yield. The application of SUB reduced nitrogen fertilizer input by 20 % while increasing sweet corn yield, contributing to higher agricultural productivity and offering an innovative strategy for the efficient management of crop straw residues. Further research is required to investigate the dynamics of straw decomposition products in enriching soil nutrients, their absorption rate by sweet corn, and their influence on soil enzyme activity and microbial community structure.