[Effects of Application of Different Organic Materials on Phosphorus Accumulation and Transformation in Vegetable Fields].

Presently, the improvement of soil organic matter is the basis to ensure food security, but the accumulation and transformation characteristics of soil phosphorus (P) as affected by organic matter remain unclear. The accumulation, transformation, and migration characteristics of soil P in different soil layers of vegetable fields were researched under the application of organic materials. Six treatments were set up in the experiment:control (no fertilization), traditional fertilizer application by farmers, biochar, chicken manure, food waste, and straw application. Available phosphorus (Olsen-P), water-soluble phosphorus (CaCl2-P) content, soil phosphorus forms, soil organic matter (SOM), and pH were determined during the pepper harvest period. In the 0-5 cm and 5-10 cm soil layers, the available phosphorus content of traditional fertilization of farmers was higher, and the available phosphorus content of the four organic materials was in the order of straw > biochar > chicken manure > food waste. Compared to that with food waste, the straw and biochar treatments increased soil available phosphorus by 59.6%-67.3% and 29.1%-36.9%, respectively. The straw treatment could easily enhance the soil labile P pool, and soil labile P in the 0-5 cm soil layer increased by 47.3% and 35.1% compared with that under the chicken manure and food waste treatments, respectively. With the increase in soil depth, the proportion of available phosphorus in the chicken manure treatment decreased the least, and available phosphorus of the 20-30 cm soil layer accounted for 55.9% of the topsoil layer but only accounted for 16.0%-34.0% under treatment with the other three materials. Compared with that under the traditional fertilization of farmers, the pH significantly increased by 0.18-0.36 units after the application of organic fertilizer, and the pH of the chicken manure and food waste treatments was significantly higher than that of biochar and straw (P < 0.05). SOM content under the biochar treatment significantly increased by 7.7%-17.6% compared to that under the other three organic materials. Among the four organic materials, the straw treatment boosted the labile P pool the most, which was conducive to the rapid increase in plant-available P. Phosphorus was most likely to migrate downward under the chicken manure treatment. In the field management based on soil fertility enhancement, the application of biochar could not only improve soil pH and SOM but also avoid excessive accumulation of phosphorus in the surface layer, which decreases environmental risks.

Optimizing the manure substitution rate based on phosphorus fertilizer to enhance soil phosphorus turnover and root uptake in pepper (Capsicum).

Introduction: In contemporary agriculture, the substitution of manure for chemical fertilizer based on phosphorus (P) input in vegetable production has led to a significant reduction in P fertilizer application rates, while, the effect of manure substitution rates on soil P transformation and uptake by root remain unclear. Methods: This research conducts a pot experiment with varying manure substitution rates (0%, 10%, 20%, 30%, 40%, 50%, 75% and 100%) based on P nutrient content to elucidate the mechanisms through which manure substitution affects P uptake in pepper. Results and discussion: The result showed that shoot and root biomass of pepper gradually increased as manure substitution rate from 10% to 40%, and then gradually decreased with further increases in the substitution rate. Soil alkaline phosphatase activity and arbuscular mycorrhizal (AM) colonization gradually increased with manure substitution rates improvement. Specifically, when the substitution rate reached 30%-40%, the alkaline phosphatase activity increased by 24.5%-33.8% compared to the fertilizer treatment. In contrast, phytase activity and the relative expression of phosphate transporter protein genes in the root system was declined after peaking at 30% manure substitution. Additionally, soil available P remained moderate under 30%-40% substitution rate, which was reduced by 8.6%-10.2% compared to that in chemical fertilizer treatment, while microbial biomass P was comparable. In the current study, soil labile P similar to or even higher than that in chemical fertilizer treatment when the substitution rate was ≤40%. Correlation heatmaps demonstrated a significant and positive relationship between soil available P and factors related to labile P and moderately labile P. Conclusion: This finding suggested that substituting 30%-40% of chemical P with manure can effectively enhance root length, AM colonization, soil enzyme activity, soil labile P, and consequently improve P uptake in pepper. These findings provide valuable insights for future organic agricultural practices that prioritize P supply, aiming to standardize organic P management in farmland and achieve high crop yields and maintain soil health.