Cover cropping has emerged as a pivotal sustainable agronomic practice aimed at enhancing soil health and sustaining crop productivity. To quantify its effects across diverse agroecosystems, we conducted a meta-analysis of 1877 paired observations from 114 studies (1980–2025) comparing cover cropping with bare fallow during fallow periods in major cereal systems across China. Cover cropping significantly reduced soil bulk density by 6.1% and increased key soil nutrients including total nitrogen (+13.1%), total phosphorus (+15.6%), hydrolysable nitrogen (+9.3%), available phosphorus (+11.1%), available potassium (+12.4%), soil organic matter (+11.7%), and microbial biomass carbon (+41.1%). Leguminous cover crops outperformed non-legumes in enhancing nitrogen availability, reflecting biological nitrogen fixation. Mixed-species cover crop mixtures showed superior benefits over monocultures, likely due to complementary effects on nutrient cycling and soil structure. Soil texture and initial soil organic carbon significantly moderated these outcomes. Furthermore, although overall soil pH remained stable, cover cropping exhibited a clear buffering effect, tending to regulate soil pH toward neutrality. Meta-regression analyses revealed a diminishing positive effect on total nitrogen (TN), available potassium (AK), and microbial biomass carbon (MBC) with an extended duration of cover cropping, suggesting potential saturation effects. These results underscore the context-dependent efficacy of cover cropping as a strategy for soil quality enhancement. Optimizing cover crop implementation should integrate the consideration of inherent soil characteristics, baseline fertility, and species composition to maximize agroecosystem resilience and sustainability.

The nitrogen (N) uptake and utilization in maize (Zea mays L.) plants are accomplished through a series of biochemical reactions and transformations involving the N assimilation enzymes. Nitrate reductase (NR) and glutamine synthetase (GS) exert important functions in the N assimilation and remobilization processes. The mechanisms underlying plant N partitioning and the associated expression patterns of NR and GS genes in maize hybrids with different N utilization efficiencies were still not clear. In this study, the expression of ZmNR and ZmGS genes that are related to N partitioning were analyzed in two maize hybrids (XY335 and HN138). Results showed that XY335 displayed higher grain yield, kernel numbers, shoot N uptake, and physiological N utilization efficiency (NUtE) than those shown in HN138 under low‐N conditions. The higher post‐silking N uptake and N remobilization in vegetative organs in XY335 were associated with the enhanced net photosynthetic rate (Pn), the NR and GS activities in ear‐leaf. Additionally, the expression levels of ZmGS1.3 and ZmGS1.4 were up‐regulated when exposed to low‐N stress, showing higher values in XY335 than those in HN138. Correlation analysis showed that the expression levels of ZmNR, ZmGS1.3, and ZmGS1.4 are correlated with leaf NR and GS activities, N remobilization, and grain yield. Our investigation suggested the critical roles of the N metabolism‐associated genes in the modulation of internal N translocation and plant productivity in maize. Future transgene analysis on ZmNR and ZmGS can provide insights into the molecular mechanisms underlying plant tolerance to low N stress in maize.

Investigating starch properties of different adzuki beans provides an important theoretical basis for its application. A comparative study was conducted to evaluate the starch content, processing, digestion, and structural quality of 12 adzuki bean varieties. The variation ranges of the 12 adzuki bean varieties with specific analyzed parameters, including the amylose/amylopectin (AM/AP) ratio, bean paste rate, water separation rate, solubility, swelling power and resistant starch (RS) content level, were 5.52–39.05%, 44.7–68.2%, 45.56–54.29%, 6.79–12.07%, 11.83–15.39%, and 2.02–14.634%, respectively. The crystallinity varied from 20.92 to 37.38%, belonging to type BC(The starch crystal type is mainly type C, supplemented by type B). In correlation analysis, red and blue represent positive and negative correlation, respectively. Correlation analysis indicated that the termination temperature of adzuki bean starch was positively correlated with AM/AP ratio. Therefore, the higher the melting temperature, the better the freeze–thaw stability. The 12 varieties were divided into Class I, Class II, and Class III by cluster analysis, based on application field. Class I was unsuitable for the diabetics’ diet; Class II was suitable for a stabilizer; and Class III was suitable for bean paste, mixtures, and thickeners. The present study could provide a theoretical basis for their application in the nutritional and nutraceutical field.

In order to solve the problem of poor uniformity of wheat strip sowing, this paper designs a positive-negative pressure wheat wide-seedling-strip-seeding precision seed metering device, which adopts the roller structure with the principle of combined positive-negative pressure. Through theoretical analysis and relevant data, the structure of the seed metering device and the structure of the positive-negative pressure air chamber were designed. The internal flow field conditions were simulated by Fluent software under different structural parameters. The design of the seed holes was completed by analyzing the pressure cloud diagram and the flow velocity vector diagram, and the optimal combination of parameters was obtained and the influence law of negative pressure on the flow field was obtained. The effect of rotational speed on the flow field was studied by EDEM-Fluent coupling technique. In this paper, a three-factor and three-level response surface test was conducted on a JPS-12 test bench with Liangxin-99 wheat as the research object. The experiment was conducted with the rotational speed of seed metering device, the negative pressure of seed suction and the seeding height as factors, and the qualified index, the reseeding index and the miss-seeding index as evaluation indicators. Through the test, the optimal structure and working parameters of the seed metering device were determined as follows: the diameter of the seed hole was 2 mm, and the number of seed holes per row was 28, negative pressure was −3.5 kPa, rotational speed of seed metering device was 19 r/min, and seeding height was 180 mm. Validation test was carried out on the optimized seed metering device: the qualified index was 80.62%, the reseeding index was 9.22%, and the miss-seeding index was 10.16%, which reached the parameter indicator in JB/T 10293-2013 Technical conditions of single seed (precision) seeder and met the agronomic requirements for wheat wide-seedling-strip-seeding. Keywords: wheat, precision, seed metering device, wheat wide-seedling-strip-seeding, positive-negative pressure, fluent, EDEM-Fluent coupling, response surface test DOI: 10.25165/j.ijabe.20221506.7261 Citation: Zhao X S, Bai W J, Li J C, Yu H L, Zhao D W, Yin B Z. Study on positive-negative pressure seed metering device for wide-seedling-strip-seeding. Int J Agric & Biol Eng, 2022; 15(6): 124–133.

Soil physical properties, nutrients, and crop yield with two-year tillage rotations under a winter wheat-summer maize double cropping system

Increasing maize planting density is considered as a potential strategy for enhancing grain yield in Northeast China; however, its yield-enhancing effects and underlying regulatory mechanisms remain inadequately characterized. Based on 508 paired observations from 42 publications, this meta-analysis quantified the effects of increased planting density on yield components and elucidated the regulatory roles of environmental and agronomic factors. Results demonstrated that increased density intensified plant competition, raising grains per ear by 43.7% and 100-kernel weight by 6.7%. The optimal regional planting density was determined to be 89,622.6 plants ha⁻¹, achieving a peak yield of 12,143 kg ha⁻¹—significantly exceeding current conventional densities (49,000–65,000 plants ha⁻¹) and highlighting substantial yield potential. Although nitrogen (N) management did not alter peak yield levels, it significantly increased the optimal density threshold (reaching 99,600 plants ha⁻¹ under high N). Among environmental factors, mean annual precipitation (MAP) was the primary constraint: yield responses to increased density were negligible in arid regions (20 g kg⁻¹) and optimal bulk density (BD) (1.25–1.40 g cm⁻³) synergistically enhanced optimal density and peak yield. This study confirms the substantial, yet context-dependent, yield potential of increasing planting density in Northeast China, providing a science-based framework for region-specific optimization.