Cadmium (Cd), as the most prevalent heavy metal contaminant poses serious risks to plants, humans, and the environment. The ubiquity of this toxic metal is continuously increasing due to the rapid discharge of industrial and mining effluents and the excessive use of chemical fertilizers. Nanoparticles (NPs) have emerged as a novel strategy to alleviate Cd toxicity. Zinc oxide nanoparticles (ZnO-NPs) have become the most important NPs used to mitigate the toxicity of abiotic stresses and improve crop productivity. The plants quickly absorb Cd, which subsequently disrupts plant physiological and biochemical processes and increases the production of reactive oxygen species (ROS), which causes the oxidation of cellular structures and significant growth losses. Besides this, Cd toxicity also disrupts leaf osmotic pressure, nutrient uptake, membrane stability, chlorophyll synthesis, and enzyme activities, leading to a serious reduction in growth and biomass productivity. Though plants possess an excellent defense mechanism to counteract Cd toxicity, this is not enough to counter higher concentrations of Cd toxicity. Applying Zn-NPs has proven to have significant potential in mitigating the toxic effects of Cd. ZnO-NPs improve chlorophyll synthesis, photosynthetic efficiency, membrane stability, nutrient uptake, and gene expression, which can help to counter toxic effects of Cd stress. Additionally, ZnO-NPs also help to reduce Cd absorption and accumulation in plants, and the complex relationship between ZnO-NPs, osmolytes, hormones, and secondary metabolites plays an important role in Cd tolerance. Thus, this review concentrates on exploring the diverse mechanisms by which ZnO nanoparticles can alleviate Cd toxicity in plants. In the end, this review has identified various research gaps that need addressing to ensure the promising future of ZnO-NPs in mitigating Cd toxicity. The findings of this review contribute to gaining a deeper understanding of the role of ZnO-NPs in combating Cd toxicity to promote safer and sustainable crop production by remediating Cd-polluted soils. This also allows for the development of eco-friendly approaches to remediate Cd-polluted soils to improve soil fertility and environmental quality.

The soil microbial community is not only driven by plant composition but is also disturbed by the soil environment. Intercropping affects the soil microenvironment through plant interaction, but the understanding of the relationship between soil microbial community and environment in intercropping is still weak. In this study, milk vetch intercropping with rapeseed was used to explore the interaction between soil microorganisms and environment. The results showed that the soil moisture content of intercropping was higher than that of monoculture during the reproductive period of rapeseed growth (flowering and podding stages). The contents of soil total nitrogen and alkali-hydrolyzable nitrogen in intercropping were higher than those in monoculture. The dominant soil microbial communities in intercropping were the same as in monoculture and included Chloroflexi, Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Gemmatimonates and Bacteroidetes. However, intercropping increased the Shannon index and decreased the Simpson’s index of the soil microbial community. The changes in the soil microbial community were mainly related to soil temperature, moisture, pH, total nitrogen, alkali-hydrolyzable nitrogen and available potassium. Moreover, there was a negative correlation between soil moisture and microorganisms and a positive correlation between nitrogen and microorganisms. Thus, milk vetch–rapeseed intercropping could not only improve soil nitrogen content, but also change soil microbial community diversity. In dryland red soil, the effect of milk vetch–rapeseed intercropping on soil moisture and nitrogen was the key factor contributing to the changes in the soil microbial community. When planting rapeseed in the future, we could consider the application of intercropping with milk vetch, which can contribute to regulating the soil nitrogen pool and improving microbial diversity.

Crop rotation has widely contributed to increasing farmland biodiversity as well as to improving soil carbon pools and microbial diversity. However, there is a weak understanding of the suitability of winter crop rotation intensification in double rice fields, especially rotation with various winter crops. For this task, a long-term field experiment based on one from 2012 was conducted with five winter crop systems for double rice: winter fallow (T0), winter milk vetch (T1), winter rape (T2), winter garlic (T3), winter rotation intensification with potato, milk vetch, and rape (T4). Parameters such as crop yield, soil carbon, nitrogen, and soil microorganism were measured. It was found that compared to winter fallow, winter milk vetch, rape, garlic, and crop rotation intensification practices increased the late rice yield by 2.5%, 2.3%, 4.5%, and 3.7%, respectively; winter garlic and crop rotation intensification also increased the early rice yield by 4.6% and 3.5%, respectively. This is associated with the promotion of rice tillering. At the same time, for winter crop rotation, compared to winter fallow, the soil organic carbon increased by 21%. With the input of diversified crop residues, winter crops were effective in soil carbon sequestration, improving soil microbial structure, and increasing soil microbial diversity. The Shannon diversity index of winter crops ranged from 9.75 to 9.91, while winter fallow was 9.38. The Simpson's diversity index of winter crops ranged from 0.997 to 0.998, while winter fallow was 0.996. In conclusion, winter crop practices, especially winter crop rotation intensification, can enhance soil health and sustainability in double rice fields through its positive feedback on crop yield, soil carbon sequestration, and microorganisms.

Corn (Zea mays L.)–soybean (Glycine max (L.) Merr.) intercropping is one of the main traditional intercropping systems used. We hypothesized that sweet corn–soybean intercropping with reduced nitrogen application could improve the crops’ fresh grain yield and nitrogen acquisition. We clarified whether sweet corn intercropped with soybean has the advantages of improved crop yield and carbon and nitrogen accumulation and assessed interspecific competition in the intercropping systems. A four-year (2017–2020) field experiment was conducted with three nitrogen application levels (0, 150, and 300 kg∙ha⁻¹) and three planting patterns (monocropped sweet corn, monocropped soybean, sweet corn–soybean intercropping) at Jiangxi Agricultural University, Nanchang, China. The LER (land equivalent ratio), AG (aggressivity), and CR (competitive ratio) were calculated using the fresh grain yield and nitrogen and carbon accumulation of sweet corn and soybean. The LER values were greater than 1.0 in most of the intercropped patterns, except for the value based on the crops’ fresh grain yield without nitrogen application in 2020. Sweet corn had greater values of CR and AG than soybean in the intercropping system. Compared with common nitrogen application (300 kg∙ha⁻¹), reduced nitrogen application (150 kg∙ha⁻¹) did not significantly reduce the LER or the average CR and AG values. Under reduced nitrogen application, the values of LER, CR, and AG, based on the crops’ fresh grain yield and nitrogen acquisition, were not significantly different between the four years. In conclusion, based on the LER, CR, and AG, sweet corn–soybean intercropping had the advantage of crop yield and nitrogen acquisition, and sweet corn was the superior competitor. Sweet corn–soybean intercropping with nitrogen application (150 kg N ha⁻¹) showed good inter-annual stability of crop productivity and competitiveness of the sweet corn.

Drought due to climate change will be more frequent and severe and expected to cause a loss of agricultural productivity in the next 30 years. Drought affects soil water availability, leading to several effects: reduction of crop growth, increases shoot/root ratio, decreases the uptake of nutrients by roots and translocation from roots to shoots, and availability of nutrients (N, P, S, Ca, Mg) in soil. The plant community regulates the composition and quantity of rhizodeposition, however, due to the impact of drought on plants functioning, allocation and fate of assimilated carbon (C) in the plant-soil-microorganisms system is changed.  Especially strong effects of drought on the functioning of soil microbial communities are seen in the crop monocultures, whereas the introduction of intercropping, especially with legumes, can potentially mitigate the drought impact. Thus, the present study aimed i) to trace the fate of rhizodeposits in the maize-soybean intercropping and compare with that in monoculture under drought vs optimal moisture conditions, ii) to reveal the differences in the rhizodeposits-C utilization by microorganisms under pulse water regime (wet to drought vs drought to rewetting).The greenhouse experiment was conducted in June-August 2021. The soils were taken from the 10-old abandoned agricultural land in Witzenhausen, sieved through 4 mm, and 3 kg were placed into the incubation pots (15x15x20 cm). Maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) were grown as monoculture (4 plants per pot) or intercropping (2+2 plants) until the vegetative stage (6-8 leaves), soil moisture was kept at 60% of WHC. Further, plants were divided into four treatments (each had four replicates), and each was labeled with K15NO3 and followed by 13C-CO2 (one day later). The treatments were: i) constant wet (60% of WHC), ii) constant drought (30% of WHC), iii) wet to drought (labeling was done under 60% of WHC and soil dried till 30% of WHC and further kept for 14d), and iv) drought to wet (labeling was done under 30% of WHC and soil was slowly rewetted to 60% of WHC and further kept for 14d). Subsamples of soils and plants aboveground biomass were done 4 times: i) 1 day after 13C-labeling, ii) after soil reached drought (30% of WHC) or 60% of WHC after rewetting, iii) in the middle of a drought or rewetting stage and iv) at the end of the experiment. Constant moisture and unlabelled treatments were sampled at the same time points; total and 13C/15N were analyzed in plant biomass, dissolved organic matter (DOM), microbial biomass, and soil; NO3- and NH4+ contents were measured in DOM extracts; additionally, activities of C, N, and phosphorus acquisition enzymes were measured. Thus, results from this experiment will shed light on the fate of rhizodeposits depending on the drought conditions and pulse water regime. The comparison of monoculture with intercropping will reveal how the presence of soybean can improve the nutrition of maize regarding N uptake, and whether microorganisms can be less affected by drought under intercropping.