Manure properties, soil conditions and managerial factors regulate greenhouse vegetable yield with organic fertilizer application across China

Organic fertilizer increases pumpkin production by improving soil fertility

Compared with long-term and continuous application of large amounts of chemical fertilizers, fertilizers with microbial organic nutrient sources can improve soil environment, increase soil fertility and increase crop yield. In view of the current low soil fertility and poor soil environment leading to low crop yield and instability in the arid regions of northwest China, the effects of organic fertilizer with microbial nutrient sources on soil nutrients and pumpkin yield were studied in 2022 and 2023 in this region. The fertilizer application level was used as control factor, with four treatments of low level (L), medium level (M), high level (H), and a conventional fertilizer control (CK). The results showed that the high application level of organic fertilizer was more beneficial to the growth of pumpkin, and the stem diameter, vine length, and leaf area of pumpkin under H treatment were the highest from 2022 to 2023. Compared to CK, the average soil bulk density was significantly decreased by 8.27-18.51% (P< 0.05); the soil organic carbon, available phosphorus, available potassium, and nitrate nitrogen under H treatment were increased by an average of 32.37%, 21.85%, 18.70%, and 36.97%, respectively. Under different organic fertilizer treatments, the pumpkin yield under M treatment was the highest, reaching 30926.18 kg·ha-1, followed by H treatment. compared to CK, M and H treatments increased the yield by 25.26% and 7.01%, respectively, and improved water use efficiency by 14.18% and 2.21%, respectively. Redundancy analysis (RDA) of soil nutrients, pumpkin growth dynamics and yield in 2022 and 2023 showed that soil organic carbon, available phosphorus, available potassium, nitrate nitrogen, and water use efficiency were significantly positively correlated with pumpkin yield (P<0.01). In conclusion, H and M treatments can improve soil fertility promote pumpkin growth and development, and ultimately increase pumpkin yield. In summary, medium organic fertilizer level (M=5700 kg·ha-1) is recommended as the fertilization scheme for local pumpkin cultivation.

Determining optimal range of reduction rates for nitrogen fertilization based on responses of vegetable yield and nitrogen losses to reduced nitrogen fertilizer application

Vegetable production is commonly accompanied by high nitrogen fertilizer rates but low nitrogen use efficiency in China. Reduced fertilization has been frequently recommended in existing studies as an efficient measurement to avoid large amount of nutrient loss and subsequent nonpoint source pollution. However, the reported responses of vegetable yield and nitrogen losses to reduced fertilization rates varied in a large range, which has resulted into large uncertainties in the potential benefits of those recommended reduction rates. Thus, we constructed the relationship between responses of nitrogen losses and vegetable yield to reduced nitrogen fertilization rates to determine the optimal range of reduction rates for nitrogen fertilization in a proportional form based on data reported in literatures across China's mainland, and evaluated the roles of greenhouse, managing options, and vegetable species on the responses. The relationships were constructed separately for 4 subregions: Northern arid and semiarid, loess plateau regions (NSL), Temperate monsoon zone (TMZ), Southeast monsoon zone (SMZ), Southwest zone (SWZ). The optimal nitrogen fertilizer reduction range for the TMZ, SMZ and SWZ were 51 % to 67 %, 40 % to 66 % and 54 % to 80 %, respectively and no reduction for NSL. Vegetable yields were not be sacrificed when fertilizations were reduced within the optimal ranges. Greenhouse and managing options showed no significant effect on the responses of both vegetable yield and nitrogen losses by the optimal reduction range but vegetable species played a relatively important role on the responses of vegetable yield. This indicated that the optimal reduction rates can be effective on reducing nitrogen loss in both open-field and greenhouse conditions across China's mainland without extra managing options. Therefore, the optimal reduction rates can still serve as a good starting point for making regional plans of nitrogen reduction that help balancing the chasing of high vegetable yield and low nitrogen loss.

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.

Organic fertilizer facilitates the soil microplastic surface degradation and enriches the diversity of bacterial biofilm

The land-use of organic fertilizers is considered as an important sustainable method for resource utilization, which may have an impact on the microplastic behaviors in the soil. Here, a 240-d dark culture experiment was conducted to reveal the degradation and biofilm characteristics of degradable and refractory granule microplastics in soil and soil-fertilizer systems. The results indicated that microplastics generally exhibited a weak weight loss as well as a specific etiolation on the surface after the culture, especially polyvinyl-chloride and polyhydroxyalkanoates (PHA). Increase in carbon-oxygen functional groups and the changes of oxygen/carbon ratios were noticed, which implied that oxidation and degradation occurred on the surface of microplastics during the cultural process. The changes were more intense on the degradable PHA, and the fertilized-soil treatment than those of the refractory microplastics and the pure soil. Moreover, the addition of organic fertilizers enriched the community diversity of bacterial biofilm on multiple microplastic surfaces. In this regard, the animal fertilizers provided a stronger effect than the plant fertilizers. Overall, the soil, fertilizer and microplastic types affected the community structure and diversity of bacterial biofilm. The outcomes of this study would provide a theoretical basis for the utilization of organic matters for agricultural soil applications.

Long-term cattle manure addition enhances soil-available phosphorus fractions in subtropical open-field rotated vegetable systems

INTRODUCTION

Evaluation of the changes in phosphorus (P) fractions (various P forms) and their availability at different soil layers is critical for enhancing P resource use efficiency, mitigating subsequent environmental pollution, and establishing a suitable manure application strategy. However, changes in P fractions at different soil layers in response to cattle manure (M), as well as a combined cattle manure and chemical fertilizer application (M+F), remain unclear in open-field vegetable systems. If the amount of annual P input remains the same, identifying which treatment would cause a higher phosphate fertilizer use efficiency (PUE) and vegetable yield while simultaneously reducing the P surplus is especially warranted.

METHODS

Based on a long-term manure experiment that started in 2008, we used a modified P fractionation scheme to analyze P fractions at two soil layers for three treatments (M, M+F, and control without fertilizer application) in an open-field cabbage (Brassica oleracea) and lettuce (Lactuca sativa) system, and assessed the PUE and accumulated P surplus.

RESULTS

The concentrations of the soil P fractions were higher in the 0-20-cm soil layer compared to the 20-40-cm layer, except for organic P (Po) and residual-P. M application significantly increased the inorganic P (Pi) (by 8.92%-72.26%) and the Po content (by 5.01%-61.23%) at the two soil layers. Compared with the control and M+F treatments, M significantly increased residual-P, Resin-P, and NaHCO3-Pi at both soil layers (by 31.9%-32.95%, 68.40%-72.60%, and 48.22%-61.04%), whereas NaOH-Pi and HCl-Pi at 0-20 cm were positively correlated with available P. Soil moderately labile-P was the predominant P component in the two soil layers (accounting for 59%-70%). With the same annual P input amount, M+CF created the highest vegetable yield (117.86 t ha-1), and PUE (37.88%) and M created the highest accumulated P surplus (128.80 kg ha^-1yr^-1).

DISCUSSION

Collectively, a combined manure-chemical fertilizer application has great potential to yield a long-term positive outcome both in terms of vegetable productivity and environmental health in open-field vegetable systems. This highlights the methods' benefits as a sustainable practice in subtropical vegetable systems. Specific attention should be given to a P balance to avoid excessive P input if a rational strategy for manure application is to be attained. This is especially the case for stem vegetables that require manure application and decreases the environmental risk of P loss in vegetable systems.