Organic fertilizers as partial substitutes for chemical fertilizers improve soil nitrogen (N) retention capacity. However, the relative importance of biotic and abiotic N immobilization at different levels of organic N substitution and the subsequent effects on N utilization in paddy soils are not well elucidated. To address these, a combination of ¹⁵N incubation experiments and pot experiments were conducted to investigate biotic and abiotic N immobilization features and their effects on N fertilizer fate under long-term different fertilization regimes in paddy soils in China. Test soils that had received chemical fertilization (NPK), chemical N was substituted with 30%, 50%, and 70% organic N (70 F + 30 M, 50 F + 50 M, and 30 F + 70 M, respectively), and no fertilization (control) for 36 years. The results revealed that both abiotic and biotic NH₄⁺-N immobilization were enhanced under organic N substitution soils. The highest NH₄⁺-N abiotic and biotic N immobilization was observed under 50 F + 50 M soil, significantly increasing by 195.5% and 51.4%, respectively, compared to the NPK soil. In contrast, only abiotic NO₃⁻-N immobilization increased with rising organic substitution N proportions. N fertilizer utilization efficiency was significantly enhanced in 50 F + 50 M soil (36.7%) compared to the NPK soil (30.3%), which was primarily attributed to the enhanced N pool activity and N immobilization capacity. However, the N fertilizer residue rate was significantly higher in the 30 F + 70 M soil (23.6%) compared to the NPK soil (21.6%), largely attributed to the soil properties improvement. Our results suggest that N immobilization capacity and N fertilizer utilization can be optimized with a 50% organic substitution ratio in our studied soil–crop system.

Habitat management using flowering plants on rice bunds and field ridges surrounding rice paddies can enhance conservation biological control by supporting beneficial predatory insects. However, multi-year field evidence for sesame (Sesamum indicum) when deployed as these bund-side flowering strips, and there is no molecular gut-content confirmation that the key predatory mirid bug Cyrtorhinus lividipennis preys upon rice planthoppers pests under field conditions. Over a two-year field experiment, we compared rice paddies with sesame-planted bunds against control paddies without bunds. We surveyed major piercing-sucking pests (brown planthoppers Nilaparvata lugens, white-backed planthoppers Sogatella furcifera, leafhoppers, and thrips) and their primary predator C. lividipennis throughout different rice phenological growth stages. PCR-based laboratory digestion assays were used to quantify the detectability of N. lugens DNA in the gut of laboratory-reared and field-collected C. lividipennis. Sesame-planted bunds significantly increased natural-enemy abundance (C. lividipennis) and reduced planthoppers, leafhopper, and thrips densities. Treatment effects varied by rice stage, with suppression mainly occurring from booting/heading to grain filling and no significant differences at tillering, and effects at maturity were weak. In the laboratory, N. lugens DNA detection declined from 68.75% at 0 h to 0% at 16 h after feeding. In the field, 37.5% of C. lividipennis from sesame-bund paddies tested positive for N. lugens DNA. These findings provide field and molecular evidence that sesame-planted bunds conserve C. lividipennis and contribute to suppression of piercing-sucking rice pests, supporting their use as an auxiliary habitat-management tactic in rice integrated pest management.

Objective Pests are one of the important factors affecting the yield and quality of maize.Evaluating the resistance level of different maize varieties to major pests has important guiding significance for the selection of insect-resistant varieties. Method In this study，we first observed the population dynamics of different pests for spring maize in Jiangxi Province，and identified the resistance to Ostrinia furnacalis and Rhopalosiphum maidis of 52 maize varieties via aphid quantity ratio method and stem hole number comparasions.Finally，insect-resistant maize varieties suitable for planting in the province were obtained through the investigation of maize yield and ear damage rate. Result we found that Mythimna loreyi，O. furnacalis，Mythimna loreyi，Spodoptera frugiperda，and R. maidis were the main pests of spring maize in Nanchang City，Jiangxi Province.Among them，the populations of corn aphid and Asian corn borer are relatively large.According to the ratio of aphid number，there were 17 high aphid-resistant varieties，5 aphid-resistant varieties，5 medium aphid-resistant varieties，6 susceptible varieties and 17 high susceptible varieties in 52 popularized varieties..According to the number of holes in the stem，there were 12 varieties with high resistance to Asian corn borer，14 varieties with resistance to Asian corn borer，12 varieties with moderate resistance，5 varieties with sensitivity and 9 varieties with high sensitivity.While the aphid resistance of some popularized maize varieties was poor，their resistance to borers was strong，while the resistance to borers was poor，their resistance to aphids was strong.However，there were three varieties（Jingke968，Shuangtian726，and Wanxiantian6188）showed highly resistance to both R. maidis and O. furnacalis.The yield of 52 varieties for 10 plants fluctuated from 0.90 kg to 4.24 kg.Wanxiantian6188，Daimuda，Weitian999，Meiyushuangtiannuo502，Jingke968 had a higher yield than other varieties.Most of the maize varieties had more than 50% of ear damage rate，except Shangmandi，Guitiannuo 108，Taitan，Baimuda and Guinuo 530. Conclusion The 52 maize varieties popularized in Jiangxi Province have different degrees of resistance to pests，and their yields under natural infection are also quite different.We found that Wanxiantian 6188 and Jingke 968 had strong resistance to aphid and O. furnacalis and higher yield in the natural insect-sensitive state.Therefore，it was recommended to plant Wanxiantian 6188 and Jingke 968 for spring maize in Jiangxi Province.These resistant varieties screened in this study provided materials and theoretical basis for breeding and popularizing maize insect-resistant varieties.