Optimizing Controlled‐Release Nitrogen Fertilizer Through Long‐Term Straw Return to Enhance Photosynthesis, Nutrient Use, and Yield in Spring Maize

ABSTRACT Straw return (SR) is a key strategy in China for recycling crop residues, improving soil fertility, and enhancing sustainable land management. Controlled‐release nitrogen fertilizer (CRN) offers an effective means to optimize nutrient use efficiency and minimize environmental losses. However, the combined influence of SR and CRN on maize ( Zea mays L.) productivity and resource‐use efficiency under intensive cropping systems remains insufficiently understood. A 2‐year split‐plot field experiment was conducted with SR and traditional planting (TP) as main plots, and five CRN rates (0, 100, 150, 200, and 250 kg ha −1 ) as subplots. Compared with TP, SR combined with CRN significantly ( p < 0.05) increased soil total nitrogen and organic carbon by 21% and 9.41%, respectively, and enhanced physiological traits, including relative chlorophyll content (SPAD, 49.36%), leaf area index (LAI, 25.41%), and dry matter accumulation (21.0%). At 200 kg ha −1 CRN, photosynthesis improved markedly, with a higher net photosynthetic rate (Pn) by 7.20%, SPAD by 3.89%, maximum photosynthetic capacity ( Fv/Fm ) by 5.16%, and photochemical quenching (qP) by 10.78% compared to TP. Grain yield recorded higher at 200 and 250 kg ha −1 CRN, and among the tested rates, 200 kg ha −1 achieved the best overall performance in yield. Overall, integrating SR with moderate CRN application improved soil fertility, promoted physiological performance, and increased maize yield while reducing nitrogen input. These results highlight the potential of combining SR with CRN fertilization to sustain land productivity and mitigate degradation risks in maize‐based agroecosystems.