peer reviewed | Soil fumigants aim to control soil-borne diseases below levels that affect economic crop production, but their use also reduces the abundance of beneficial microorganisms. Previous studies have shown that adding various types of fertilizers to soil after fumigation can reshape the soil microbial community and regulate crop growth. We fumigated soil with dazomet (DZ) that had been cropped continuously for more than 20 years. After fumigation we applied silicon fertilizer, potassium humate organic fertilizer, Bacillus microbial fertilizer or a mixture of the last two. We studied the effects of different fertilizers treatments on the soil's physicochemical properties, enzyme activities, key soil pathogens and beneficial microbes. We found that fertilizers applied after fumigation promoted soil beneficial microorganisms (such as Fimicutes, Chloroflexi, Bacillus and Actinomadura) restoration; increased Fusarium and Phytophthora pathogen mortality, the content of ammonium nitrogen, sucrase enzyme activity; and increased strawberry fruit yield. A significant increase in strawberry yield was positively correlated with increases in beneficial microorganisms such as Gemmatimonadota, Firmicutes, Bacillus and Flavisolibacter. We concluded that organic fertilizer applied after fumigation significantly increased the number of beneficial microorganisms, improved the physicochemical properties of the soil, increased soil enzyme activities, inhibited the growth of soil pathogens to increase strawberry fruit yield. In summary, organic fertilizer activated soil beneficial microorganisms after soil fumigation, promoted soil health, and increased strawberry fruit yield. © 2021

peer reviewed | Soil-borne diseases have become increasingly problematic for farmers producing crops intensively under protected agriculture. Although soil fumigants are convenient and effective for minimizing the impact of soil-borne disease, they are most often detrimental to beneficial soil microorganisms. Previous research showed that bio-activation of soil using biological control agents present in biofertilizers or organic fertilizers offered promise as a strategy for controlling soil-borne pathogens when the soil was bio-activated after fumigation. Our research sought to determine how bio-activation can selectively inhibit pathogens while promoting the recovery of beneficial microbes. We monitored changes in the soil's physicochemical properties, its microbial community and reductions in soil-borne pathogens. We found that the population density of Fusarium and Phytophthora were significantly reduced and tomato yield was significantly increased when the soil was bio-activated. Soil pH and soil catalase activity were significantly increased, and the soil's microbial community structure was changed, which may have enhanced the soil's ability to reduce Fusarium and Phytophthora. Our results showed that soil microbial diversity and relative abundance of beneficial microorganisms (such as Sphingomonas, Bacillus, Mortierella and Trichoderma) increased shortly after bio-activation of the soil, and were significantly and positively correlated with pathogen suppression. The reduction in pathogens may have been due to a combination of fumigation-fertilizer that reduced pathogens directly, or the indirect effect of an optimized soil microbiome that improved the soil's non-biological factors (such as soil pH, fertility structure), enhanced the soil's functional properties and increased tomato yield.

Growing applications of nanoagrichemicals have resulted in their increasing accumulation in agricultural soils, which could modify soil properties and affect soil health. A greenhouse pot trial was conducted to determine the effects of three metallic nanoagrichemicals on several fundamental chemical properties of a rice paddy soil, including zinc oxide nanoparticles (ZnO NPs) and copper oxide nanoparticles (CuO NPs) at 100 mg/kg, and silicon oxide nanoparticles (SiO₂ NPs) at 500 mg/kg, as well as their bulk and ionic counterparts. The investigated soil amendments displayed significant and distinctive impact on the examined soil chemical properties relevant to agricultural production, including soil pH, redox potential, soil organic carbon (SOC), cation exchange capacity (CEC), and plant available As. For example, all amendments increased the bulk soil pH at day 47 to some extent, but the increase was substantially higher for SiO₃²⁻ (37.7%) than other amendments (5.8%–13.7%). Soil Eh was elevated markedly at day 47 after the addition of soil amendments in both the bulk soil (45.9%–74.4%) and rice rhizosphere soil (20.3%–68.9%). CuO NPs and Cu²⁺ generally exhibited greater impact on soil chemical properties than other agrichemicals. Significantly different responses to soil amendments were observed between bulk and rhizosphere soils, suggesting the essential role of plants in affecting soil properties and their responses to environmental disturbance. Overall, our results confirmed that the tested amendments could have remarkable impacts on the fundamental chemical properties of rice paddy soils.

Earthworms and arbuscular mycorrhizal fungi (AMF) act synergistically in the rhizosphere and may increase host plant tolerance to Cd. However, mechanisms by which earthworm-AMF-plant partnerships counteract Cd phytotoxicity are unknown. Thus, we evaluated individual and interactive effects of these soil organisms on photosynthesis, antioxidant capacity, and essential nutrient uptake by Solanum nigrum, as well as on soil quality following Cd exposure (0–120 mg kg⁻¹). Decreases in biomass and photosynthetic activity, as well as nutrient imbalances were observed in Cd-stressed plants; however, the addition of AMF and earthworms reversed these effects. Cd exposure increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, whereas inoculation with Rhizophagus intraradices decreased those. Soil enzymatic activity decreased by 15–60% with increasing Cd concentrations. However, Cd-mediated toxicity was partially reversed by soil organisms. Earthworms and AMF ameliorated soil quality based on soil enzyme activity. At 120 mg kg⁻¹ Cd, the urease, catalase, and acid phosphatase activities were 1.6-, 1.4-, and 1.2-fold higher, respectively, in soils co-incubated with earthworms and AMF than in uninoculated soil. Cd inhibited shoot Fe and Ca phytoaccumulation, whereas AMF and earthworms normalized the status of essential elements in plants. Cd detoxification by earthworm-AMF-S. nigrum symbiosis was manifested by increases in plant biomass accumulation (22–117%), chlorophyll content (17–63%), antioxidant levels (SOD 10–18%, POD 9–25%, total polyphenols 17–22%, flavonoids 15–29%, and glutathione 7–61%). It also ameliorated the photosynthetic capacity, and macro- and micronutrient statuses of plants; markedly reduced the levels of malondialdehyde (20–27%), superoxide anion (29–36%), and hydrogen peroxide (19–30%); and upregulated the transcription level of FeSOD. Thus, the combined action of earthworms and AMF feasibly enhances metal tolerance of hyperaccumulating plants and improves the quality of polluted soil.

Evidence of microplastic (MP) pollution in Antarctic terrestrial environments reinforces concerns about its potential impacts on soil, which plays a major role in ecological processes at ice-free areas. We investigated the effects of two common MP types on soil physicochemical properties and microbial responses of a marine terrace from Fildes Peninsula (King George Island, Antarctica). Soils were treated with polyethylene (PE) fragments and polyacrylonitrile (PAN) fibers at environmentally relevant doses (from 0.001% to 1% w w−1), in addition to a control treatment (0% w w−1), for 22 days in a pot incubation experiment under natural field conditions. The short-term impacts of MPs on soil physical, chemical and microbial attributes seem interrelated and were affected by both MP dose and type. The highest PAN fiber dose (0.1%) increased macro and total porosity, but decreased soil bulk density compared to control, whereas PE fragments treatments did not affect soil porosity. Soil respiration increased with increasing doses of PAN fibers reflecting impacts on physical properties. Both types of MPs increased microbial activity (fluorescein diacetate hydrolysis), decreased the cation exchange capacity but, especially PE fragments, increased Na+ saturation. The highest dose of PAN fibers and PE fragments increased total nitrogen and total organic carbon, respectively, and both decreased the soil pH. We discussed potential causes for our findings in this initial assessment and addressed the need for further research considering the complexity of environmental factors to better understand the cumulative impacts of MP pollution in Antarctic soil environments.

In situ remediation technology applied aims to not only decrease cadmium (Cd) and arsenic (As) uptake by rice but also improve soil health and rice quality in contaminated paddy soils. Here the effects of a combined amendment, consisting of limestone, iron powder, silicon fertilizer, and calcium-magnesium-phosphate fertilizer, with three application rates (0, 450, and 900 g m⁻²) on soil health, rice root system, and brown rice quality were compared in moderately versus highly Cd and As co-contaminated paddy fields. After the amendment application, soil pH, cation exchange capacity, four kinds of soil enzyme activities increased (sucrase, urease, acid phosphatase, and catalase), and concentrations of leached Cd/As decreased, as measured by the DTPA (diethylene triamine pentaacetic acid) and TCLP (toxicity characteristic leaching procedure). Changes in the above soil indicators promoted soil health. In both fields, the dithionite-citrate-bicarbonate (DCB)-Fe and DCB-Mn concentration in iron plaque increased and root length became longer. Changes in the above root system indicators reduced the root system's absorption of Cd and As but increased that of nutrients. Under 900 g m⁻² treatment, the Cd concentration in brown rice of two sites decreased by 55.8% and 28.9%, likewise inorganic As (iAs) decreased by 50.0% and 21.1%, whereas essential amino acids increased by 20.4% and 20.0%, respectively. Furthermore, the Cd and iAs concentrations in brown rice were <0.2 mg kg⁻¹ (maximum contaminant level of Cd and iAs in the Chinese National Food Safety Standards GB2762-2017 for brown rice) under the 900 g m⁻² in the moderately contaminated field. These results suggest the combined amendment can improve soil health and brown rice quality in the moderately and highly Cd- and As-co-contaminated paddy soils, offering potential eco-friendly and efficient remediation material for applications in such polluted paddy soils.

Soil-borne diseases have become increasingly problematic for farmers producing crops intensively under protected agriculture. Although soil fumigants are convenient and effective for minimizing the impact of soil-borne disease, they are most often detrimental to beneficial soil microorganisms. Previous research showed that bio-activation of soil using biological control agents present in biofertilizers or organic fertilizers offered promise as a strategy for controlling soil-borne pathogens when the soil was bio-activated after fumigation. Our research sought to determine how bio-activation can selectively inhibit pathogens while promoting the recovery of beneficial microbes. We monitored changes in the soil’s physicochemical properties, its microbial community and reductions in soil-borne pathogens. We found that the population density of Fusarium and Phytophthora were significantly reduced and tomato yield was significantly increased when the soil was bio-activated. Soil pH and soil catalase activity were significantly increased, and the soil’s microbial community structure was changed, which may have enhanced the soil’s ability to reduce Fusarium and Phytophthora. Our results showed that soil microbial diversity and relative abundance of beneficial microorganisms (such as Sphingomonas, Bacillus, Mortierella and Trichoderma) increased shortly after bio-activation of the soil, and were significantly and positively correlated with pathogen suppression. The reduction in pathogens may have been due to a combination of fumigation-fertilizer that reduced pathogens directly, or the indirect effect of an optimized soil microbiome that improved the soil’s non-biological factors (such as soil pH, fertility structure), enhanced the soil’s functional properties and increased tomato yield.

Microplastics (MPs) as emerging persistent pollutants have been a growing global concern. Although MPs are extensively studied in aquatic systems, their presence and fate in agricultural systems are not fully understood. In the agricultural soils, major causes of MPs pollution include application of biosolids and compost, wastewater irrigation, mulching film, polymer-based fertilizers and pesticides, and atmospheric deposition. The fate and dispersion of MPs in the soil environment are mainly associated with the soil characteristics, cultivation practices, and diversity of soil biota. Although there is emerging pollution of MPs in the soil environment, no standardized detection and quantification techniques are available. This study comprehensively reviews the sources, fate, and dispersion of MPs in the soil environment, discusses the interactions and effects of MPs on soil biota, and highlights the recent advancements in detection and quantification methods of MPs. The prospects for future research include biomagnification potency, cytotoxic effects on human/animals, nonlinear behavior in the soil environment, standardized analytical methods, best management practices, and global policies in the agricultural industry for the sake of sustainable development.

The rapid global plastic production of 348 million tonnes in 2018 has led to widespread environmental pollution, especially in terrestrial ecosystems. This study examines microplastics in agricultural soils, coming alarmingly. Particles ≤5 mm, which are defined as microplastics, have detrimental effects on the earth’s environment. Because of its ecological importance, soil acts as an important microplastic sink, affecting soil and plant health and microbial activity. A variety of factors contribute to microplastic pollution in agricultural soils, including plastic mulching, manure, agricultural products (silage nets, twine), sewage sludge, weathering, and other indirect processes. These microplastics migrate, threatening soil integrity and biodiversity. Soil microplastics are analyzed for size, volume fraction, and polymer. Common materials include polyethylene, polypropylene, polyamide, polystyrene, polyvinyl chloride, and polyesters. Techniques, including optical microscopy and spectroscopy, extract and analyze microplastics. This comprehensive review calls for increased concern about the ecological effects of microplastics in agricultural soils. It emphasizes the importance of managing plastics to solve environmental challenges. The integrated environmental assessment highlights the complex relationship between microplastics and soil ecosystems, providing insights into potential risks and suggesting strategies to combat this looming environmental threat.