Under the condition of straw returning to the field, appropriate nitrogen fertilizer application is one of the key factors used to improve crop yield and ensure environmental safety. Therefore, an experiment with different rates of nitrogen fertilization was conducted with a randomized block design in Harbin, China. The straw was deeply plowed back into the field after harvest in the autumn. The nitrogen application rates were 0, 75, 150, 180, 225, and 300 kg·ha⁻¹. The purpose of this study is to clarify the appropriate amount of nitrogen fertilizer under the condition of straw returning to the field and to provide technical support for high-yield and high-efficiency maize in cold regions. The results indicated that the yield of maize first increased and then stabilized as the amount of nitrogen fertilizer increased, while the economic benefits first increased and then decreased. When the nitrogen application rate exceeds 225 kg·ha⁻¹ or is lower than 150 kg·ha⁻¹, the economic benefits significantly decrease. When high-nitrogen fertilizer rates of 225 kg·ha⁻¹ and 300 kg·ha⁻¹ were applied, the residual nitrate nitrogen in the soil was increased by 2.1 times and 2.3 times, respectively, compared to before sowing. With the increase in the nitrogen application rate, the nitrogen fertilizer utilization efficiency and agronomic efficiency decreased, and the apparent nitrogen loss and nitrogen surplus significantly increased. Comprehensively considering the maize yield, benefits, and environmental risk factors the suitable nitrogen application rate was in a range of 170.2 kg·ha⁻¹ to 178.2 kg·ha⁻¹ in the first year and 150.0 kg·ha⁻¹ to 171.3 kg·ha⁻¹ in the second year. This work provides a theoretical basis and technical support for the rational application of nitrogen fertilizer and high-yield and high-efficiency spring maize under the condition of straw returning to the field.

With global economic development and rising living standards, expectations regarding the quality of staple rice have become increasingly multifaceted. This shift has imposed more stringent demands on high-quality rice breeding and field management and has stimulated research into the mechanisms underlying changes in rice quality. This article explores how assessments of rice quality have evolved from a primary emphasis on appearance, eating and processing quality to include stronger requirements for nutritional value and safety. In rice production systems, quality outcomes are influenced by interactions among genetic traits, ecological factors and field management practices. Through genetic improvement, biological breeding techniques and precise field management, improvements in appearance, eating and nutritional qualities can be achieved. Although climate change is an uncontrollable external factor affecting rice quality, constructing multi-factor dynamic simulation models that target key genes has been proposed as a strategy to enhance stress resistance and guide rice breeding. Rice safety and quality depend on the rational use of pesticides in terms of timing and dosage, which can help mitigate disease and insect resistance while reducing the risks associated with pesticide residues and toxins. Furthermore, the application of artificial intelligence technologies in biological breeding and field management can shorten breeding cycles, improve disease and pest outbreak prediction and support the timely formulation of treatment prescriptions.