This study aimed to explore the effects of combining new bio-breeding insect-resistant varieties with dense-planting precision-controlled high-yield technology on maize yield and economic benefits, and to propose the optimal cultivation mode suitable for new bio-breeding insect-resistant varieties, so as to provide the theoretical basis for optimizing the high-yield and high-efficiency cultivation system of spring maize in the Xiliaohe Plain.

Through a field trial in Tongliao, Inner Mongolia from 2023 to 2024, the experiment was conducted in a split-zone design, with cultivation mode as the main zone, setting up two modes of local traditional farmer mode (FP) and dense planting precision regulation mode (DPDI); varieties as the sub-zone, four maize varieties were used, namely, Dongdan 1331 (DD1331), Dongdan 1331K (DD1331K), Youdi 919 (YD919), Youdi 919HZ (YD919HZ). Then, the impact of varietal insect resistance traits on maize yield and economic benefits under different technical models were analyzed.

During a two-year trial, the insect pests in the fields of insect-resistant varieties occurred lightly, with the insect plant rate of 6.80%-9.87%; the fields of conventional varieties occurred moderately or heavily, with the insect plant rate of 22.27%-36.31%. In 2023 (insect plant rate>30%), compared with conventional varieties (DD1331, YD919), the new insect-resistant varieties (DD1331K, YD919HZ) significantly increased thousand kernel weight, thus improving maize yield (0.84%-9.31%) and economic benefits (0.3%-13.3%), whereas in 2024, when the insect plant rate was about 23%, there was no significant difference in the number of thousand kernels and the number of grains between insect-resistant varieties, and there were no significant differences in ear grain number, thousand kernel weight and yield between conventional varieties. With increasing planting density, maize yield reached its maximum at 9.0×10⁴ or 10.5×10⁴ plants/hm², which was significantly higher than that at 6.0×10⁴ plants/hm² density, by 13.54%-19.94% and 7.48%-21.01%, respectively. The two-year average yields of the dense planting precision regulated model were significantly higher than those of the traditional farmers' model, with yield increases ranging from 13.50% to 19.19% in 2023 and from 7.03% to 14.42% in 2024. Compared with the traditional farmers' model, the economic benefits of the dense planting precision regulation model were generally improved by 0.19×10⁴-1.02×10⁴ yuan/hm².

Insect-resistant varieties (DD1331K, YD919HZ) significantly improved yield (up to 9.31%) and economic efficiency (up to 40.3%) in years of severe insect infestation (>30% of insect plants), but did not differ significantly from conventional varieties under low insect pressure. Through optimized density (9.0×10⁴-10.5×10⁴ plants/hm²) and precise management of water and fertilizer, DPDI increased yields by an average of 22.18% in two years and improved economic benefits by 0.57×10⁴ yuan/hm² compared with the conventional mode (FP); the core principle of DPDI was that insect resistant varieties could reduce the threat of pests, decrease yield losses, reduce the use of insecticides, and lower production input costs. By increasing the production capacity of maize populations through reasonable planting density and combining drip irrigation with water and fertilizer integration for precise regulation, the yield and income of maize could be increased. The synergistic application of insect-resistant varieties and DPDI model could achieve technological superposition and further improve the ability of high and stable yield.

The North China Plain is the thermal resource limited area, summer maize grain mechanical harvesting technology were astricted by higher grain moisture content at harvest stage, which affects the quality of mechanical grain harvest. Under delayed harvest conditions, nitrogen application rate affect summer maize grain yield, and superior and inferior grains morphology and weight are not clear. Through the systematic observation of summer maize superior and inferior grains morphology, filling and dehydration process under different nitrogen application levels, clarified the regulation effect of nitrogen, and which provided support for summer maize grain mechanical harvesting technology cultivation to obtain stabilize yield, reduce nitrogen application and improve efficiency in the of region.

Summer maize grain mechanical harvesting hybrid Jingnongke 728 was used as the research materials, the field experiment were conducted in 2020-2021 by a harvest time and nitrogen application rate two-factor randomized block design, harvest time were normal harvest time (NH) and delayed harvest (DH), and six nitrogen application rate were 0 (N₀), 120 (N₁₂₀, 2021), 180 (N₁₈₀), 240 (N₂₄₀), 300 (N₃₀₀), 360 (N₃₆₀) and 450 kg hm^-2 (N₄₅₀, 2020). Summer maize grain yield (GY), superior and inferior grains fresh volume (GFV), fresh weight (GFW), dry weight (GDW), and moisture content (GMC) and their change rates were measured.

Compared to the dry year (2020), the inferior grains maximum grain filling rate (G_max), the increment at G_max (W_max) and initial potential (R₀) of GFV, GFW and GDW were significantly reduced in the rainy year (2021), and the days reached G_max (T_max) were delayed, and the active duration (P) were prolonged, which resulted in GFV, GFW and GDW reduced significantly by 15.4%-50.6%, 25.4%-62.0% and 31.2%-57.3%, respectively, however, there were no significant change in superior grains, and so led GY declined significantly by 3.03×10³-5.44×10³ kg·hm^-2. The inferior grains GDW_Gmax, GDW_Wmax and GDW_R0 in the rainy year were significantly decreased by 55.1%-258.1%, 13.4%-143.0% and 12.0%-126.6%, respectively, and GDW_Tmax were delayed by 4.2-20.7 d compared to superior grains. The superior grains GFV, GFW and GDW were significantly increased by 56.8%-69.6%, 67.0%-80.4% and 54.1%-92.1%, respectively, than inferior grains. Compared with NH, the grains G_max and R₀ at DH treatments were increased, and the P for superior and inferior grains were significantly prolonged, which led the GFV, GFW decreased significantly by 2.1%-8.1% and 12.2%-17.1%, 4.0%-5.2% and 15.7%-19.5, respectively, under the dry year and rainy year, meanwhile GDW increased from 25.1-28.2 g/100 grains to 28.0-34.4 g/100 grains, the GMC decreased from 22.6%-26.0% to 22.6%-26.0% as well, which were declined by 31.3%-40.4% than NH. The GY for DH were increased 0.02×10³-1.67×10³ kg·hm^-2 than NH. There was no significant difference in GFV, GFW and GDW between nitrogen application levels in dry year. While in the rainy year, the GDW_Gmax and GDW_Wmax for N₂₄₀-N₃₆₀ treatment were significantly higher than N₁₈₀, GDW_Tmax were delayed, and GDW_P was prolonged (P<0.05), and the effects were more intense on inferior grains than on superior grains. Under DH treatment, the GFV, GFW and GDW of inferior grains for N₂₄₀–N₃₆₀ were significantly increased by 25.7%-85.3%, 59.4%-83.6% and 17.9%–43.9% than N₁₈₀, respectively. The nitrogen yield increasing effect in rainy year were significantly intense than dry year, as 74.4%-169.5% vs. 51.5%-99.1%. GY of N₂₄₀ was significantly rised by 12.6%-54.5% than N₁₂₀-N₁₈₀.

In the thermal resource limited area of the North China Plain, changed winter wheat into spring wheat in the wheat–maize cropping system, with summer maize delayed harvest for 23-33 days, the inferior grains capacity and weight were significantly increased, and so the grain moisture content were reduced to the grain mechanical harvesting technology standard to realized the annual grain mechanical harvesting. And by optimized nitrogen application rate at 247.2-248.6 kg·hm^-2, the production strategy of stable yield at 7.0×10³-12.0×10³ kg·hm^-2, nitrogen reduction and improve efficiency under different rainfall years were achieved in the region.