Exogenous carbon addition is widely regarded as an effective soil management strategy for rapidly increasing soil organic carbon, improving soil structure and function. However, a systematic comparison of the effects of diverse organic amendments on key soil attributes and processes is needed to inform their targeted application. We evaluated the impacts of seven organic amendments (biochar, organic fertilizer, corn straw, soybean straw, rapeseed straw, green manure, and carbon material) on a purple soil (Luvic Xerosols) in a pot experiment. The results showed that organic fertilizer and carbon material performed best in enhancing soil nutrient availability and promoting soil organic carbon content. Straw amendments promoted the formation of macro-aggregates. Green manure and straws enhanced carbon transformation-related β-glucosidase and cellobiohydrolase activities. Random Forest and structural equation modeling indicated that the organic amendments enhanced maize carbon sequestration capacity and biomass by improving aggregate stability and regulating the fungal community and by increasing nutrients and enhancing active carbon fractions. Green manure and organic fertilizer demonstrated the most significant agronomic effects. These findings provide guidelines for targeted organic amendment selection in purple soil regions.

Thirty-one nodulating rhizobium strains were collected from root nodules of spring and winter type faba bean cultivars grown in micro ecoarea, i.e. the same field in Chengdu plain, China. The symbiotic efficiency and phylogeny of these strains were studied. Effectively nitrogen fixing strains were isolated from both winter type and spring type cultivars. Based on phylogenetic analysis of 16S rRNA gene and concatenated sequence of atpD, glnII and recA genes, the isolates were assigned as Rhizobium anhuiense and a potential new Rhizobium species. The isolates were diverse on symbiosis related gene level, carrying five, four and three variants of nifH, nodC and nodD, respectively. Strains carrying similar gene combinations were trapped by both winter and spring cultivars, disagreeing with the specificity of symbiotic genotypes to reported earlier faba bean ecotypes.

Optimization of nitrogen (N) fertilizer application is essential to achieve higher crop yields at lower environmental costs. This study investigated the impacts of N application rates (0, 180, and 360 kg N ha⁻¹) on maize productivity, N use efficiency (NUE), NO₃⁻-N leaching, cumulative N₂O emissions, and N surplus in maize growing in the purple soil of Southwest China through a 2-year field study. The critical N rate balancing yield optimization with reduced NO₃⁻-N leaching and N₂O emissions was identified. The results showed that grain yield initially increased linearly and then stabilized with increasing N rates, while NUE significantly decreased. NO₃⁻-N leaching, N₂O emissions, and N surplus exhibited quadratic increase. Regression analysis indicated that 158–163 kg N ha⁻¹ achieved optimal yield while maintaining acceptable NO₃⁻-N leaching and N₂O emissions compared to 360 kg N ha⁻¹. This range also enhanced NUE and minimized soil N residue.

The fruits of kiwifruit are well known for their abundant nutritional value and health benefits, but kiwifruit vines are susceptible to environmental factors such as drought or waterlogging. Optimum substrate moisture content (SMC) can decrease cultivation costs and improve the quality of seedlings in soilless cultivation. To quantify the water requirements of kiwifruit seedlings, a greenhouse study was conducted to investigate the growth, antioxidant defense, and photosynthetic parameters of seedlings of Actinidia valvata Dunn at six levels of SMC (20%, 40%, 60%, 80%, 100%, and 120%). Results showed that shoot and root dry matter accumulation increased gradually with the increase in SMC from 20% to 100% and was lower at 120% SMC than at 100% SMC. Electrolyte leakage and malondialdehyde content were the lowest at 80% and 100% SMC. Antioxidant enzyme activities, including superoxide dismutase, peroxidase, and catalase, chlorophyll content, net photosynthetic rate, maximal quantum yield of PSII photochemistry, photosynthetic electron transfer rate, and actual quantum yield were the highest at 80% and 100% SMC, but there was no significant difference in these parameters between the two treatments (80% and 100% SMC). However, the shoot and root dry weights of seedlings at 100% SMC were 13.20% and 33.02% higher than those at 80% SMC, respectively. In summary, 100% SMC provided optimal water supply for the photosynthetic efficiency and dry matter accumulation of shoots and roots. The results are expected to be useful for the mass production of high-quality kiwifruit seedlings in greenhouse or nursery containers, with the potential to save water.

Phosphate fertilizer is essential for crop production but poses environmental risks in agriculture. The agronomic and environmental thresholds for phosphorus application in Southwest China’s purple soils (Luvic Xerosols) remain poorly defined. We combined soil phosphorus fractionation, root phenotyping, and microbial community analysis (16S rRNA and ITS amplicon sequencing) to explore soil–microbe–plant interactions in a 12-year field experiment with five P application rates (0, 37.5, 75, 112.5 and 150 kg P₂O₅ ha⁻¹ yr⁻¹). Results showed that beyond 75 kg ha⁻¹, the medium-soluble phosphorus pool increased significantly while stable phosphorus decreased. Fungal diversity was more sensitive to high phosphorus than bacterial diversity. Maize yield plateaued at 75–150 kg ha⁻¹, mainly due to increased grain weight and optimized root architecture. An environmental risk threshold was identified at 83.54 kg ha⁻¹ and an optimal yield threshold at 84.65 kg ha⁻¹, enabling high yield with low environmental risk via microbially mediated phosphorus activation. Therefore, this research reveals that the phosphorus input threshold can provide a basis for reducing phosphorus application, regulating phosphorus components, and maintaining microbial diversity and network complexity in purple soil dryland farming systems, thereby ensuring maize yield.