•This study compared soil quality indices based on a set of 12 indicators.•Soil quality index was developed using SOC, MBC, TK, Eh, and Mn(II).•Mn(II) was the dominant soil quality factor, ...contributing 34.24 % to the SQI value and represents the redox state of the soil.•This study is beneficial for implementing rice-crayfish practices and management of rice planting areas.
In order to employ appropriate management measures for rice-crayfish farming systems in the Jianghan Plain, it is critical to evaluate how this process affects the soil quality. By taking 76 soil samples from three different crayfish aquaculture periods (≥10 years (Y10), 4-6 years (Y4), and 1–2 years (Y1)) from paddy fields and using traditional rice planting patterns as controls (rice-wheat, rice-grape, and rice monoculture as CK), we surveyed the influence of different years of rice-crayfish development in rice fields on the soil quality using an integrated soil quality index (SQI). The results showed that crayfish aquaculture significantly affected the soil quality of the paddy fields. The SQI assessed the soil organic carbon (SOC), microbial biomass carbon (MBC), total potassium (TK), oxidation-reduction potential (Eh), and Mn(II). The highest SQI values were detected in the Y10 rice-crayfish system, and the lowest in the traditional paddy field. Mn(II) was the dominant soil quality factor, contributing 34.24 % to the SQI value. The relativity analysis also demonstrated that the SQI values were inversely correlated with Mn(II), and this may be used as a characteristic indicator to evaluate the soil quality of rice-crayfish systems in paddy fields. Overall, crayfish aquaculture in rice fields significantly improved the soil quality. The findings of this research showed that the use of a minimum data set (MDS), the SQI, is a potent means for assessing the soil quality of rice-crayfish systems.
The relative severity between chromium (Cr)-mediated ecotoxicity and its bioaccumulation has rarely been compared and evaluated. This study employed pot incubation experiments to simulate the soil ...environment with increased Cr pollution and study their effects on the growth of crops, including pepper, lettuce, wheat, and rice. Results showed that increasing total Cr presented ascendant ecotoxicity in upland soils when pH > 7.5, and significantly reduced the yield of pepper, lettuce and wheat grain by 0.3–100 %, whereas, this effect was weakened even reversed as the pH decreased. Surprisingly, a series of soils with Cr concentration of 22.7–623.5 mg kg-1 did not cause Cr accumulation in four crops over the Chinese permissible limit. The toxicity of Cr was highly associated with extractable Cr, where Cr (VI) made the greater contributions than Cr (III). Conclusively, the ecotoxicity of Cr poses a greater environmental issue as compared to the bioaccumulation of Cr in crops in upland soils, while extractable Cr (VI) makes the predominant contributions to the ecotoxicity of Cr as the total Cr increased. Our study proposes a synchronous consideration involving total Cr and Cr (VI) as the theoretical basis to establish a more reliable soil quality standard for safe production in China.
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•Hexavalent chromium (Cr) was proposed for optimizing Chinese soil quality standard.•Ecotoxicity of Cr posed a greater issue as compared to accumulation of Cr in crops.•Extractable Cr, especially Cr (VI), dominantly determined the ecotoxicity of Cr.•Increasing total Cr reduced crop yield by up to 100.0 % in upland soils on pH > 7.5.•Paddy soil facilitated reduction of Cr (VI) and subsequent adsorption of Cr (III).
Plants release a wide set of secondary metabolites including volatile organic compounds (VOCs). Many of those compounds are considered to function as defense against herbivory, pests, and pathogens. ...However, little knowledge exists about the role of belowground plant VOCs for attracting beneficial soil microorganisms. We developed an olfactometer system to test the attraction of soil bacteria by VOCs emitted by Carex arenaria roots. Moreover, we tested whether infection of C. arenaria with the fungal pathogen Fusarium culmorum modifies the VOCs profile and bacterial attraction. The results revealed that migration of distant bacteria in soil towards roots can be stimulated by plant VOCs. Upon fungal infection, the blend of root VOCs changed and specific bacteria with antifungal properties were attracted. Tests with various pure VOCs indicated that those compounds can diffuse over long distance but with different diffusion abilities. Overall, this work highlights the importance of plant VOCs in belowground long-distance plant-microbe interactions.
•As a weighting method for soil quality evaluations, MRA method was superior to PCA.•Soil quality evaluations should be specific to crop and soil types.•The MDS for navel orange orchards includes ...SOM, silt, pH, AB and AK.•The use of lime, and organic, K, and B fertilizers is important in orchards.
Soil quality evaluations based on crop yields can provide clear guidance for managing agricultural production. Navel oranges are widely cultivated around the world. However, systematic soil quality evaluations for navel orange orchards have not been reported. This study uses two weighting methods, principle component analysis (PCA) and multiple regression analysis (MRA), to evaluate the soil quality of navel orange orchards in central subtropical China. The PCA weighting method is widely used for evaluating soil quality. In contrast, the MRA weighting method, which is linked closely with crop yield, is rarely used. A variety of soil samples, representing the spatial homogeneity in 114 navel orange orchards of Xinfeng County, Jiangxi province, were collected and analyzed for 17 frequently used chemical and physical properties. Result showed that the sensitivity and accuracy of the MRA weighting method were superior to those of the PCA weighting method. Thus, the MRA weighting method was recommended for future soil quality assessments. The soil indicators retained in the minimum data set (MDS) included SOM, silt, pH, AB and AK. The MDS indicators changed with the crop and soil types. Therefore, future soil quality evaluations should be specific to the crop and soil types. Overall, the soil quality of the studied navel orange orchards was low or moderate. Thus, more efforts should be directed towards adding lime and organic, potassium (K) and boron (B) fertilizer in navel orange production management.
ABSTRACT Brazilian soil scientists have increased the use of the term “soil quality” in their scientific publications in the last decade. However, it remains unclear if those publications only ...mention “soil quality” in a broad context, or the studies are focused on soil quality assessments, integrating soil chemical, physical and biological indicators. The objective of this systematic review was to carry out a critical analysis of the conception in using the term “soil quality” in recent publications derived from studies performed in Brazil. For this purpose, the terms (“soil health” or “soil quality” or “qualidade do solo”) and (“Brazil*” or “Brasil*”) were searched in databases of Web of Science, Scopus, and Scielo from 2014 to 2021. Initially, 1,284 peer-reviewed papers were found, subsequently selected according to the criteria established in two filters: (i) First filter - studies carried out in Brazil, which mentioned at least one of the terms of interest (“soil health” or “soil quality” or “qualidade do solo”) and that evaluated soil biological, physical or chemical indicators, assessing at least one of them; (ii) Second filter - studies in which all three groups of soil indicators were assessed and integrated, and presented a specific discussion about soil quality. According to the results, 36 % of the papers met the first criteria (n = 464), and only 2 % (n = 30) attended the second filter. The terms “soil health” or “soil quality” or “qualidade do solo” were mentioned 7 and 37 times per paper for those papers selected in the first and second filter, respectively. We evidenced in our study that the term soil quality in agricultural science papers has been predominantly used in a broad context, mostly to refer to the suitable soil conditions for plant growth. Thus, we concluded that even if the use of soil quality term is increasing in Brazilian literature, there are still very few researchers working specifically with soil quality assessments, in its full conception (i.e., integrating chemical, physical and biological indicators). Therefore, there is a promising research field to be explored to promote scientific advances in the soil quality area (e.g., new concepts, assessment frameworks, on-farm monitoring protocols), as well as disseminate the soil quality assessment among the Brazilian farmers, environmentalists, and other stakeholders.
Microorganisms associated with roots are thought to be part of the so-called extended plant phenotypes with roles in the acquisition of nutrients, production of growth hormones, and defense against ...diseases. Since the crops selectively enrich most rhizosphere microbes out of the bulk soil, we hypothesized that changes in the composition of bulk soil communities caused by agricultural management affect the extended plant phenotype. In the current study, we performed shotgun metagenome sequencing of the rhizosphere microbiome of the peanut (Arachis hypogaea) and metatranscriptome analysis of the roots of peanut plants grown in the soil with different management histories, peanut monocropping and crop rotation. We found that the past planting record had a significant effect on the assembly of the microbial community in the peanut rhizosphere, indicating a soil memory effect. Monocropping resulted in a reduction of the rhizosphere microbial diversity, an enrichment of several rare species, and a reduced representation of traits related to plant performance, such as nutrients metabolism and phytohormone biosynthesis. Furthermore, peanut plants in monocropped soil exhibited a significant reduction in growth coinciding with a down-regulation of genes related to hormone production, mainly auxin and cytokinin, and up-regulation of genes related to the abscisic acid, salicylic acid, jasmonic acid, and ethylene pathways. These findings suggest that land use history affects crop rhizosphere microbiomes and plant physiology.
This research focuses on two science-based soil quality assessments, i.e., visual soil assessment (VSA) and analytical (lab-based) soil quality (SQ) assessment. The VSA, especially when conducted by ...farmers, offers a cost-effective approach to studying soil in extended study areas. However, little is known about the applicability of VSA in areas subjected to different degradation processes. Our study takes place in the lowland, midland, and highland agro-ecological zones (AEZs) of the Shafe and Sile-Elgo catchments, in the Southern Main Ethiopian Rift Valley. It aims to contribute to the state-of-art knowledge on VSA by evaluating its reproducibility when conducted by farmers and extensionists and its correlation to analytical SQ indicator scores, and to generate insight into SQ of the cropland in the various AEZs of two selected catchments. To that aim, 36 cropland fields were selected, half of these fields receiving soil and water conservation (SWC) practices, while no SWC was applied to the others. In each field, the VSA was conducted by farmers and experts, followed by laboratory analyses and calculation of an SQ index. Our finding reveals that overall VSA scores assigned by both groups were very strongly correlated (r=0.909–0.975, p<0.001) and reproducible at any level of stratification in the highly diverse, tropical study area covered in this research. However, the VSA indicator soil texture turned out to be non-reproducible. Both VSA and analytical SQ indicator scores are significantly (p<0.05) higher in fields receiving SWC practices and integrating both methods provided a clear contrast between fields that have good and poor SQ conditions in different AEZs of the catchments. The VSA method is less capable of capturing problems related to toxicities or low nutrient and water availability as a consequence of acidity, salinity and sodicity. Therefore, when the VSA method is applied to monitor SQ status of fields subjected to diverse degradation processes, it would be better to include specific indicators of pH and EC.
•Visual soil assessment proves applicable in environmentally diverse catchments.•Visual and analytical soil quality assessments are distinctive for management.•Visual techniques offer a more comprehensive assessment of soil compaction.•Integrated assessments can evaluate soil quality for a wider range of threats.
•Biochar studies were assessed relating to experiment and crop types, biochar and soil condition.•Despite most studies in developed countries soils are less impaired than in developing ...countries.•Wood and municipal wastes were major biochar sources compared to crop residues and manures.•Averaged across many scientific studies, biochar increases crop yields ∼20% with about 10tha−1.•Strong collaboration is required globally to advance the research and adoption of biochar.
Multiple nutrient deficiencies related to severe soil fertility depletion have emerged as the major constraint to the sustainability of agriculture on a global scale. Use of biochar and biochar-compost mixtures from different alternative organic sources have been proposed as an option for improving soil fertility, restoring degraded land, and mitigating the emissions of greenhouse gasses associated with agriculture. We review the findings of 634 publications in the last decade on biochar and biochar-compost mixtures as soil amendments in order to identify the potential gaps in our understanding of the role of these amendments in agriculture. We found that: i) the majority of published studies have been carried out in developed countries where soils are less impaired in terms of food production capacity than in many developing countries; ii) studies on biochar produced in small kilns are more common than biochars produced at commercial scale in developed countries, whereas biochars produced using traditional techniques are more commonly used than biochars produced in modern pyrolysis units in developing countries; iii) laboratory and greenhouse studies are more common than field studies; and iv) wood and municipal wastes were the major feedstock for the preparation of biochar compared to crop residues and manures. Although, biochar-compost application proved to be more generally effective in improving soil properties and crop yields (field crops and horticulture crops) than biochar alone, along with desired soil properties, could be a feasible alternative to remediate the degraded soils and improve their productivity potential in the long-term. Overall, a lack of long-term, well-designed field studies on the efficacy of biochar and biochar-compost mixtures on different soil types and agro-climatic zones are limiting our current understanding of biochar's potential to enhance crop production and mitigate climate change. We further suggest that greater collaboration between researchers, biochar producers, and policy makers is required to advance the research and uptake of this important technology at a global scale.
Global crop yields are limited by water and nutrient availability. Soil mulching (with plastic or straw) reduces evaporation, modifies soil temperature and thereby affects crop yields. Reported ...effects of mulching are sometimes contradictory, likely due to differences in climatic conditions, soil characteristics, crop species, and also water and nitrogen (N) input levels. Here we report on a meta-analysis of the effects of mulching on wheat and maize, using 1310 yield observations from 74 studies conducted in 19 countries. Our results indicate that mulching significantly increased yields, WUE (yield per unit water) and NUE (yield per unit N) by up to 60%, compared with no-mulching. Effects were larger for maize than wheat, and larger for plastic mulching than straw mulching. Interestingly, plastic mulching performed better at relatively low temperature while straw mulching showed the opposite trend. Effects of mulching also tended to decrease with increasing water input. Mulching effects were not related to soil organic matter content. In conclusion, soil mulching can significantly increase maize and wheat yields, WUE and NUE, and thereby may contribute to closing the yield gap between attainable and actual yields, especially in dryland and low nutrient input agriculture. The management of soil mulching requires site-specific knowledge.
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