Cucumber downy mildew (CDM) is a destructive plant disease caused by the air-borne oomycete pathogen Pseudoperonospora cubensis. CDM causes severe yield reduction of cucumber and significant economic losses. Biocontrol is a promising method to control CDM with the advantage of being beneficial to sustainable agricultural development. However, until now, no reviews of biocontrol of CDM have been reported. The objective of this review is to more comprehensively understand the biocontrol of CDM. In this review, the biological characteristics of P. cubensis are introduced, and strategies for screening biocontrol agents to suppress CDM are recommended. Then the current biocontrol agents, including fungi such as Trichoderma and biocontrol bacteria such as Bacillus, which possess the ability to control CDM, and their control characteristics and ability against CDM are also summarized. The potential mechanisms by which these biocontrol agents prevent CDM are discussed. Finally, several suggestions for future research on the biocontrol of CDM are provided.

Three damaging soybean diseases, Sclerotinia stem rot caused by a fungus Sclerotinia sclerotiorum (Lid.) de Bary, Phytophthora root rot caused by a fungus Phytophthora sojae, and soybean cyst nematode (Heterodera glycines Ichinohe), are destructive to soybean growth and yield and cause huge economic losses. Biocontrol is an effective way to control soybean diseases with the advantage of being environmentally friendly and sustainable. To date, few reviews have reported the control of these three soybean diseases through biocontrol measures. In this review, the biological characteristics of the three pathogens and the incidence features of the three soybean diseases were first introduced. Then, biocontrol agents containing fungi and bacteria capable of controlling the three diseases, as well as their control abilities, were emphasized, followed by their mechanisms of biocontrol action. Bacillus and Streptomyces were found to possess the ability to control all three soybean diseases under greenhouse or field conditions. Finally, suggestions about screening new biocontrol species and deeply studied biocontrol molecular mechanisms are provided for further research on the biocontrol of soybean diseases.

Humic acids (HAs) incorporated into urea fertilizers are highly effective at increasing yield and decreasing fertilizer-derived nitrogen (N) loss from soil, but reports of the optimal proportion in fertilizers remain widely inconsistent. In this study, we examined the effects of urea enhanced with 0.2–5.0% HAs (UHAs) on the yield, biomass production, N uptake, and N residue in fluvo-aquic soil in winter wheat cultivated over two growing seasons from 2018 to 2020 in the North China Plain. UHAs application significantly enhanced wheat grain yield, aboveground dry biomass, total and fertilizer-derived N uptake by wheat, and residue in soil, while reducing the loss of fertilizer-derived N. Additionally, UHAs treatments increased fertilizer-N residues in soil, especially in the top 30 cm soil layer, which increased with the proportion of added HAs. These positive effects were attributed to a higher spike number under UHAs treatments compared to conventional urea. Clustering analysis of the different treatments showed that 0.2% HAs were more similar to conventional urea, while 0.5% had similar effects to HAs at higher proportions. UHAs application significantly enhanced wheat grain yield, mainly via increasing spike number, and optimized the fertilizer-N fate. Among UHAs treatments, 0.5% HAs showed the highest increase in economic benefit.

Studies of soil DNA-based and RNA-based bacterial communities under contrasting long-term fertilization regimes can provide valuable insights into how agricultural management affects soil microbial structure and functional diversity. In this study, soil bacterial communities subjected to six fertility treatments in an alkaline soil over 27 years were investigated by 454 pyrosequencing based on 16S rDNA and 16S rRNA. Long-term fertilization showed significant influences on the diversity of the soil DNA-based bacteria, as well as on their RNA-based members. The top five phyla (Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, and Planctomycetes) were found in both the DNA- and RNA-based samples. However, the relative abundances of these phyla at both DNA and RNA levels were showed significantly different. Analysis results showed that the diversity of the 16S rRNA samples was consistently lower than that of the rDNA samples, however, 16S rRNA samples had higher relative abundance. PICRUSt analysis indicated that glycan biosynthesis and metabolism were detected mainly in the DNA samples, while metabolism and degradation of xenobiotics and the metabolism of amino acids, terpenoids and polyketides were relatively higher in the RNA samples. Bacilli were significantly more abundant in all the OM-fertilized soils. Redundancy analysis indicated that the relative abundances of both DNA- and RNA-based bacterial groups were correlated with soil total organic carbon content, nitrogen content, Olsen-P, and soil pH. Moreover, the RNA-based Bacilli were positively correlated with available phosphorus (Olsen-P).

Land application of livestock manure may reduce the use of mineral fertilizers and alleviate the environmental degradation associated with mineral fertilizers application. However, how to optimize utilization of livestock manure value is not well understood and documentation regarding the nitrogen (N) and phosphorus (P) fertilizer replacement values (NFRV and PFRV, respectively) needs further scrutiny. Therefore, three representative livestock manures, i.e., pig, chicken, and cattle manure, were applied at different usages to assess their N and P availability in comparison to reference mineral fertilizers over summer maize growing seasons. The results show that the average NFRVs of pig, chicken, and cattle manures were 41.7–58.4%, 27.5–44.4%, and −3.6–36.1%, respectively, when based on different references (grain yield, total dry matter yield, grain N uptake, total N uptake), at different N application levels. The NFRV increased with the elevated N application rate for cattle manure treatment. In the P trials, livestock manure had a higher PFRV at a low P application level, and the average PFRVs of pig, chicken, and cattle manures were 80.3–164.8%, 77.9–143.7%, and 94.1–168.0%, respectively, at different P application levels. We conclude that livestock manure produced the lowest NFRV and highest PFRV at a low fertilizer application rate; pig manure had the highest N availability; and cattle manure had the highest P availability.