Affect Soil Health Research Articles

Application of Phosphorus and Zinc affecting soil health after cultivation of Green gram (Vigna radiata L.) Var. MD Vikas in an Inceptisol of Prayagraj

The objective of the present study was to determine the impact of Phosphorus and Zinc on soil nutrient status following green gram crop cultivation. The experiment was analyzed under a Randomized Block Design consisting of nine treatments replicated thrice with three different levels of Phosphorus and Zinc (0% P, 50% P, 100% P, and 0% Zn, 50% Zn, 100% Zn) respectively. The results showed that increasing application of Phosphorus and Zinc enhanced Db (Mg m-3), Pore space (percent), Organic Carbon (percent), Available Nitrogen (kg ha-1), Available Phosphorus (kg ha-1), Available Potassium (kg ha-1), and Available Zinc (mg kg-1). On the other hand, DP (Mg m-3), pH of the soil, EC (dS m-1), and Water retaining capacity (%) decreased It was discovered that Db (Mg m3), Dp (Mg m-3), pH of the soil, and Pore space decrease in depth. Also, reduction in depth increased Water retaining capacity (%), EC (dS m-1), OC (%), Available Nitrogen (kg ha-1), Available Phosphorus (kg ha-1), Available Potassium (kg ha-1), and Available Zinc (mg kg-1)

The effect of the use of a soil improver based on waste brown coal on the enzymatic activity of soil in the cultivation of Paulownia hybrids (Paulownia Siebold & Zuccarini, 1835)

The effect of the use of a soil improver based on waste brown coal on the enzymatic activity of soil in the cultivation of Paulownia hybrids (Paulownia Siebold & Zuccarini, 1835). An important element in controlling the condition of the soil and the plants grown on it are tests of the enzymatic activity of the soil matrix. One of the greatest advantages of using enzyme tests is the ability to make an assessment that also includes other non-measurable factors that affect soil health and condition. The diagnosed changes in soil enzymatic activity are the best parameter for determining the biochemical processes taking place there. This article describes the enzymatic activity of lessive soils on which the Paulownia hybrid variety is cultivated and a soil improver based on waste brown coal is used

Soil Fertility Changes With Climate and Island Age in Galápagos: New Baseline Data for Sustainable Agricultural Management

While the extended absence of human influence has led to matchless natural conditions on the Galápagos archipelago, agricultural activities on the inhabited islands are increasingly affecting soil health and functioning. However, a systematic assessment of the agricultural soils on the Galápagos Islands is still absent. Plate tectonics and hotspot volcanism cause an eastward drift of the archipelago and result in a west-to-east soil age gradient from approx. 1 to 1,000 ka. In addition, precipitation regimes change from arid to humid with elevation on the higher-standing islands. The objective of this study was to investigate differences in soil fertility parameters and Mehlich (III)-extractable nutrient levels along these gradients in order to provide baseline information for sustainable agricultural management. Topsoil samples (0–20 cm) from 125 farms of the islands Isabela, Santa Cruz and San Cristóbal were analyzed. Gravel and sand content, pH, electrical conductivity, cation exchange capacity, base saturation, soil organic C and total N content tended to decrease with increasing island age, while clay content, soil macroaggregate stability, plant-available water and bulk density increased. Mehlich (III)-extractable base cations Ca, K, Mg and Na as well as P, Fe and Zn showed a decreasing tendency from the youngest to the oldest island, while Mn increased with island age. Mehlich (III)-extractable Cu and Na reached their highest levels on the most intensively farmed, intermediate-aged island Santa Cruz, likely related to anthropogenic inputs and irrigation with brackish water, respectively. Changes along the altitudinal climate gradient within the studied islands were most significant for soil pH, base saturation, and Mehlich (III)-extractable Ca and Mn. Our results highlight the importance of site-specific agricultural management to account for the strong heterogeneity in soil parameters among and within the Galápagos archipelago. The data provided herein shall serve as a baseline for targeted future management strategies to avoid soil degradation, restore and maintain soil functioning and, hence, sustain the soils’ provision of ecosystem services in this unique archipelago.

The role of different organic amendments to improve maize growth in wastewater irrigated soil

Wastewater irrigation in croplands is recognized as one of the major threat, seriously affecting soil health and sustainable agriculture around the globe. Heavy metals presence especially cadmium (Cd) in wastewater irrigated soils is posing serious physiological and morphological disorder in plants due to its highest mobility. Therefore, metals mobility in wastewater irrigated soils can be curtailed through eco-friendly and cost effective organic soil amendments compost (CP), press mud (PM) and moringa leaf extract (ME) at 3% rate that eventually reduces its translocation from polluted soil to plant. This study explored the possible effects of various types of organic soil amendments on Cd phytoavailability in wastewater degraded soil and its subsequent accumulation in maize tissues. Maize plant was grown in Ghazi University as a test plant and Cd accumulation was recorded in its tissues, translocation from root to shoot, chlorophyll contents, plant biomass, yield and soil properties (pH, NPK, OM and Soluble Cd) were also examined. Results revealed that the addition of amendments significantly minimized Cd mobility in soil by 45.8%, 23% and 19.4% when CP, PM and ME were added at 3% over control. Comparing the control soil, Cd uptake effectively reduced via plants shoots by 33.3%, 27.7% and 19.4% when CP, PM and ME. In addition, NPK were significantly increased among all the added treatments in the soil-plant system as well as improved chlorophyll contents relative to non-treated soil. The Current study suggested that among all the amendments, compost at 3% rate performed well and can be considered a suitable approach for maize growth in polluted soil.

Compositional Shift of Bacterial, Archaeal, and Fungal Communities Is Dependent on Trophic Lifestyles in Rice Paddy Soil.

The soil environment determines plants’ health and performance during their life cycle. Therefore, ecological understanding on variations in soil environments, including physical, chemical, and biological properties, is crucial for managing agricultural fields. Here, we present a comprehensive and extensive blueprint of the bacterial, archaeal, and fungal communities in rice paddy soils with differing soil types and chemical properties. We discovered that natural variations of soil nutrients are important factors shaping microbial diversity. The responses of microbial diversity to soil nutrients were related to the distribution of microbial trophic lifestyles (oligotrophy and copiotrophy) in each community. The compositional changes of bacterial and archaeal communities in response to soil nutrients were mainly governed by oligotrophs, whereas copiotrophs were mainly involved in fungal compositional changes. Compositional shift of microbial communities by fertilization is linked to switching of microbial trophic lifestyles. Random forest models demonstrated that depletion of prokaryotic oligotrophs and enrichment of fungal copiotrophs are the dominant responses to fertilization in low-nutrient conditions, whereas enrichment of putative copiotrophs was important in high-nutrient conditions. Network inference also revealed that trophic lifestyle switching appertains to decreases in intra- and inter-kingdom microbial associations, diminished network connectivity, and switching of hub nodes from oligotrophs to copiotrophs. Our work provides ecological insight into how soil nutrient-driven variations in microbial communities affect soil health in modern agricultural systems.

Wheat Straw Incorporation Affecting Soil Carbon and Nitrogen Fractions in Chinese Paddy Soil

Soil organic carbon (SOC) and nitrogen (N) fractions greatly affect soil health and quality. This study explored the effects of wheat straw incorporation on Chinese rice paddy fields with four treatments: (1) a control (CK), (2) a mineral NPK fertilizer (NPK), (3) the moderate wheat straw (3 t ha−1) plus NPK (MSNPK), and (4) the high wheat straw (6 t ha−1) plus NPK (HSNPK). In total, 0–5, 5–10, 10–20, and 20–30 cm soil depths were sampled from paddy soil in China. Compared with the CK, the HSNPK treatment (p < 0.05) increased the C fraction content (from 13.91 to 53.78%), mainly including SOC, microbial biomass C (MBC), water-soluble organic C (WSOC), and labile organic C (LOC) in the soil profile (0–30 cm), and it also (p < 0.05) increased the soil N fraction content (from 10.70 to 55.31%) such as the soil total N (TN) at 0–10 cm depth, microbial biomass N (MBN) at 0–20 cm depth, total water-soluble N (WSTN) at 0–5 and 20–30 cm depths, and total labile N (LTN) at 0–30 cm depth. The primary components of soil LOC and LTN are MBC and MBN. Various soil C and N fractions positively correlated with each other (p < 0.05). The HSNPK treatment promoted the soil MBC, WSOC, and LOC to SOC ratios, and also promoted MBN, WSTN, and LTN to soil TN ratios at a depth of 0–20 cm. To summarize, the application of HSNPK could maintain and improve rice paddy soil quality, which leads to increased rice grain yields.

Elucidating the impact of three metallic nanoagrichemicals and their bulk and ionic counterparts on the chemical properties of bulk and rhizosphere soils in rice paddies

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.

Quantifying soil organic carbon’s critical role in cereal productivity losses under annualized crop rotations

Understanding the impact of soil degradation on crop productivity is essential for decision-makers to predict agronomic, economic, and environmental outcomes of agricultural operations. Soil organic carbon (SOC) is influenced by the cropping system and affects soil health through its effect on other soil physical, chemical, and biological properties. Data from a 56-year long-term experiment in Uruguay’s Pampa region were analyzed to quantify the effects of soil degradation on wheat (Triticum aestivum L.), and barley (Hordeum vulgare) yields. A significant degree of soil degradation was generated by six rotations with variable annual crop and pasture proportions (0%, 33%, 50%, and 66% of non harvest pasture). Yield records (n = 368) and annual values of 14 explanatory variables containing soil, climatic, and management indicators were evaluated using random forest regressions. Rotation-induced SOC variation ranged from 1.2% to 2.6%, and robust relationships between SOC, soil physical, chemical, and biological properties were established. Over time, yields increased in crop pasture systems but plateaued for the annualized crop rotation (0% pasture). Yield improvements due to agronomic technology advances partly mask soil degradation effects. SOC losses lead to a reduction in yield, even when the SOC level was above 2%. Thus, no critical level of SOC could be determined. SOC interacted with climate indicators to impact yield. This analysis confirms the central role of SOC in yield outcomes beyond nutrient availability, and its potential to represent a wide range of soil functions. Our findings indicate that crop rotations with a higher percentage annual vs. perennial crops negatively impact SOC, associated soil properties, and yield potential.

Lignin reinforced, water resistant, and biodegradable cassava starch/PBAT sandwich composite pieces

Abstract Following the stipulation to replace nondegradable plastics with biodegradable materials in China, cost-effective and water-resistant packaging materials have become increasingly necessary. In this work, lignin reinforced thermoplastic cassava starch (TPS) pieces were prepared by filling glycerol and lignin powder into starch via a melt blending process and then being pressed into thin pieces. A mechanical properties test showed that following the addition of 3 wt% lignin, the tensile strength of the TPS piece was improved to 16.15 MPa from 3.71 MPa of the original TPS piece. The porous structures of the lignin powder tie the TPS macromolecular chains, induce higher crystallization, and thus provide higher tensile strength and lower elongation at break. After sandwiching two pieces of poly (butylene adipateco-terephthalate) (PBAT)/peanut shell powder composite thin film to each side of the TPS piece, the PBAT/TPS/PBAT sandwich gains excellent water resistance properties. However, as soon as the sandwich piece is cut into smaller ones, they absorb water quickly, implying such pieces can be biodegraded rapidly. These characteristics make it especially suitable for use in the preparation of cabinet waste bags, which are generally stirred into organic fertilizer with the cabinet waste. Slow degradation may negatively affect soil health and farm production.

Road to successful floriculture through soil micronutrient mapping of different zones of India

The present scenario for natural resource conservation demands for crop diversification and efficient management of natural resources, viz. water, nutrient, soil. The horticultural crops are always looked upon for diversification and within horticultural crops; fruits and vegetables are given prime importance for nutritional value and high outputs. Floricultural crops have emerged as potent livelihood crops for small and marginal farmers, employment for youth with low inputs, crop diversification and natural resource management. The improper use of inputs, viz. fertilizer and water in floral crops limits their production and can adversely affect soil health. So floriculturists should work on this least attended area and recommend appropriate fertilizers to flower growers for good quality production. In comparison to other crops, the nutrient requirement of floral crops is more due to which they scavenge more nutrients from soil so large amount of these nutrients are needed to replenish the soil to maintain balance. The critical limits of micronutrients for different agronomic crops have been developed and same are used for floricultural crops too but as requirement of these crops is higher so critical limits for floral crops need to be developed. Keeping in view all above, an attempt has been made to map micronutrient status of major flower producing states that could be used in management of micronutrient requirement of different floral crops. This will further help in development of policies pertaining to sound micronutrient management packages and precision fertilization in floriculture.

Effect of Climate Change on Soil Health and Implications on Food Security: A Review

Climate change and soil health are intertwined complex processes that affect each other. The aim of this review was to find out the impact of climate change on soil health, its implication on food security and human welfare across the globe. The study found out that soil health is affected by land use practices and several anthropogenic activities carried out on landscapes; climate change and variability. Soil health also contributes to soil water retention, crop productivity, households’ food and income security culminating into a large contribution towards achieving sustainable development goals across the globe. Soil components affect climate and climate affects soil health and human wellbeing. The review article concluded that climate change and soil health are complex and intertwined multidisciplinary processes that require multidisciplinary approaches for better understanding and improvement of crop production. Appropriate climate smart agricultural practices are recommended to enhance soil health and mitigate and adapt to the changing climate for the improved farmers’ income, food security and human wellbeing across the globe.

A chronosequence of soil health under tallgrass prairie reconstruction

Soil health changes induced by prairie reconstruction (cultivated fields to tallgrass prairie) were assessed in Central Missouri within sites representing a chronosequence of 0, 2, 3, 4, 6, 9, 10, 11, 12, and 13-yr post-reconstruction. In addition, a nearby remnant native prairie, two long-term reconstructed prairies (~25 and ~57-yr post-reconstruction), and a biofuel prairie 9-yr post-reconstruction were evaluated for comparative purposes. From 0 to 8-yr, prairie reconstruction increased soil aggregation, total soil organic carbon (SOC), total nitrogen (TN), active C and N (permanganate oxidizable C and total protein), and mineralizable C and N (soil respiration and potentially mineralizable nitrogen), becoming more similar to levels in the remnant prairie. Further, four enzymes involved in the cycling of C (β-glucosidase), N (β-glucosaminidase), P (acid phosphatase), and S (arylsulfatase) demonstrated amplified activities within samples collected to a depth of 15-cm. Over time, the ratios of active C to SOC and active N to TN declined, reflecting the conversion of active C/N pools into more stable C/N pools due to continued organic inputs and increased microbial activity. In contrast, from 8- to 13-yr post-reconstruction, the number of these same soil health indicators declined, which may be attributed to historical land use, the improvement of prairie reconstruction and management strategies, and ecological processes related to succession. Overall, prairie reconstruction holds great potential for soil health restoration in degraded agricultural landscapes, and further study is needed to understand how historical land use and prairie reconstruction practices affect soil health and ecological resilience.

Land Uses, Altitude and Texture Effects on Soil Parameters. A Comparative Study in Two Districts of Nagaland, Northeast India

Northeast (NE) India is a typical tropical ecosystem with a luxuriant forest vegetation cover, but nowadays forests are under stress due to exploitation and land use changes, which are known to affect soil health and productivity. However, due to a scarcity of data, the influence of land uses and altitude on soil properties of this peculiar ecosystem is poorly quantified. This study presents the changes in soil properties in two districts of Nagaland (Mon and Zunheboto) in relation to land uses (forest, plantation, jhum and fallow jhum), altitude (<500 m, 500–1000 m, >1000 m) and soil texture (coarse, medium, fine). For this, a random soil sampling was performed in both the districts. Results indicated that soil organic carbon (SOC) stocks and available potassium (K) were significantly influenced by land uses in the Mon district, while in Zunheboto a significant difference was observed in available phosphorus (P) content. SOC stocks showed an increasing trend with elevation in both districts. The influence of altitude on P was significant and the maximum concentration was at lower elevations (<500 m). In Mon, soil texture significantly affected SOC stocks and the available N and P content. The variability in soil properties due to land uses, altitudinal gradients and textural classes can be better managed with the help of management options, which are still needed for this ecosystem.

Agricultural Soil Management Practices Differentially Shape the Bacterial and Fungal Microbiome of Sorghum bicolor.

Soils play important roles in biological productivity. While past work suggests that microbes affect soil health and respond to agricultural practices, it is not well known how soil management shapes crop host microbiomes. To elucidate the impact of management on microbial composition and function in the sorghum microbiome, we performed 16S rRNA gene and ITS2 amplicon sequencing and metatranscriptomics on soil and root samples collected from a site in California's San Joaquin Valley that is under long-term cultivation with 1) standard (ST) or no tilling (NT) and 2) cover-cropping (CC) or leaving the field fallow (NO). Our results revealed that microbial diversity, composition, and function change across tillage and cover type, with a heightened response in fungal communities, versus bacterial. Surprisingly, ST harbored greater microbial alpha diversity than NT, indicating that tillage may open niche spaces for broad colonization. Across management regimes, we observed class-level taxonomic level shifts. Additionally, we found significant functional restructuring across treatments, including enrichment for microbial lipid and carbohydrate transport and metabolism and cell motility with NT. Differences in carbon cycling were also observed, with increased prevalence of glycosyltransferase and glycoside hydrolase carbohydrate active enzyme families with CC. Lastly, treatment significantly influenced arbuscular mycorrhizal fungi, which had the greatest prevalence and activity under ST, suggesting that soil practices mediate known beneficial plant-microbe relationships. Collectively, our results demonstrate how agronomic practices impact critical interactions within the plant microbiome and inform future efforts to configure trait-associated microbiomes in crops.Importance While numerous studies show that farming practices can influence the soil microbiome, there are often conflicting results on how microbial diversity and activity respond to treatment. In addition, there is very little work published on how the corresponding crop plant microbiome is impacted. With bacteria and fungi known to critically affect soil health and plant growth, we concurrently compared how the practices of no and standard tillage, in combination with either cover-cropping or fallow fields, shape soil and plant-associated microbiomes between the two classifications. In determining not only the response to treatment in microbial diversity and composition, but for activity as well, this work demonstrates the significance of agronomic practice in modulating plant-microbe interactions, as well as encourages future work on the mechanisms involved in community assemblages supporting similar crop outcomes.

Current understanding of subsurface transport of micro‐ and nanoplastics in soil

AbstractEnvironmental problems caused by plastic pollution in terrestrial systems have received increasing attention, especially the issues related to micro‐ and nanoplastics. Soils are a major receptacle and reservoir of plastics, and accumulated plastics can negatively affect soil health. In this short review, we discuss the current state of knowledge of subsurface transport of micro‐ and nanoplastics in soils. We discuss the fundamental transport mechanisms for micro‐ and nanoplastics and highlight the peculiarities of environmentally relevant micro‐ and nanoplastics. Plastic particles >10 μm are generally filtered out in soil, but smaller plastic particles have the potential to move through soil. Larger plastics in soil will break down into micro‐ and nanoplastics over time due to environmental weathering reactions, making the plastics more prone to subsurface transport. Moreover, interactions with microorganisms and dissolved organic matter may render micro‐ and nanoplastics more hydrophilic, thereby facilitating subsurface transport. Further, soil organisms can move plastic particles by bioturbation, and plastics themselves can affect soil hydraulic properties. Although much of the past research has focused on transport of pristine plastic particles, focus should be given to environmentally relevant plastics, considering the complexities of irregular shape, polydisperse size, and heterogenous surface properties, as well as the temporal changes of these properties caused by continuous environmental modifications.

Efficiency of different types of biochars to mitigate Cd stress and growth of sunflower (Helianthus; L.) in wastewater irrigated agricultural soil.

Cadmium contamination in croplands is recognized one of the major threat, seriously affecting soil health and sustainable agriculture around the globe. Cd mobility in wastewater irrigated soils can be curtailed through eco-friendly and cost effective organic soil amendments (biochars) that eventually minimizes its translocation from soil to plant. This study explored the possible effects of various types of plants straw biochar as soil amendments on cadmium (Cd) phytoavailability in wastewater degraded soil and its subsequent accumulation in sunflower tissues. The studied biochars including rice straw (RS), wheat straw (WS), acacia (AC) and sugarcane bagasse (SB) to wastewater irrigated soil containing Cd. Sunflower plant was grown as a test plant and Cd accumulation was recorded in its tissues, antioxidant enzymatic activity chlorophyll contents, plant biomass, yield and soil properties (pH, NPK, OM and Soluble Cd) were also examined. Results revealed that addition of biochar significantly minimized Cd mobility in soil by 53.4%, 44%, 41% and 36% when RS, WS, AC and SB were added at 2% over control. Comparing the control soil, biochar amended soil effectively reduced Cd uptake via plants shoots by 71.7%, 60.6%, 59% and 36.6%, when RS, WS, AC and SB. Among all the biochar, rice husk induced biochar significantly reduced oxidative stress and reduced SOD, POD and CAT activity by 49%, 40.5% and 46.5% respectively over control. In addition, NPK were significantly increased among all the added biochars in soil–plant system as well as improved chlorophyll contents relative to non-bioachar amended soil. Thus, among all the amendments, rice husk and wheat straw biochar performed well and might be considered the suitable approach for sunflower growth in polluted soil.

Response of soil organic carbon and soil health indicators to treated wastewater irrigation in bioenergy sorghum production on an arid soil

AbstractTreated urban wastewater (WW) reuse for crop irrigation is seen as an way to mitigate prolonged drought effects and reduced freshwater (FW) availability for agriculture in arid west Texas. However, the impacts of WW on arid soil health are not clearly understood. This field study evaluated the effects of WW irrigation on soil health indicators including soil organic carbon (SOC), permanganate oxidizable carbon (POXC), mineralizable carbon (MC), and soil protein under bioenergy sorghum production. Water type and gypsum + sulfur application were used as main and subplot factors in a split‐plot experimental design with growth year as a repeated measure. Results across time and soil amendments showed that the SOC of WW‐irrigated soils (3.26 g kg−1) was significantly higher than that of FW‐irrigated soils (2.96 g kg−1). This signifies the positive impact of WW to contribute to soil carbon with no associated priming effects. Wastewater and soil amendment application by themselves did not affect other soil health indicators, given their soil salinization potential. Irrespective of the water type and amendment application, soil POXC significantly increased from 245 to 262 mg kg−1 over time, indicating that a labile pool of C was added to the soil. Soil protein concentrations significantly decreased from 1.31 to 1.23 g kg−1 after 2 years, possibly due to mineralization of organic nitrogen. In conclusion, our results demonstrate that WW application did not adversely affect soil health in the short term. Long‐term studies could provide more insight into the sustained effects of WW irrigation on arid soil health.

Cytogenetic toxicity from pesticide and trace element mixtures in soils used for conventional and organic crops of Allium cepa L.

Pesticides and trace elements occur in complex mixtures in agroecosystems, affecting soil health and food security. Hence, it is necessary to determine their toxicity in field conditions and to develop monitoring approaches to assess conventional and organic agriculture. The aim of this research was to evaluate the associations between Allium cepa L. cytogenetic biomarkers and the realistic mixture of pesticides and trace elements found in soils of conventional, conversion, and organic crops in an intensive agricultural region in Colombia. Pesticide screening was conducted using GC-MS/MS and LC-MS/MS methods. Arsenic, cadmium, lead, and zinc were analyzed by ICP-MS; chromium, copper, nickel, and selenium by ICP-OES; and mercury by a direct analyzer. The meristematic cells in roots of Allium cepa L. were analyzed through microscopic observations to quantify cytogenetic effects. In conventional crops, 26 pesticides were detected in the soil samples, and those were below the limit of quantification in organic crops. The mean levels of As, Cd, Cr, Ni, Pb, and Se were also greater in soils of conventional crops compared to the organics. In addition, the biomarkers of cytotoxicity and genotoxicity appeared augmented in conventional samples, and those were correlated with pesticide and trace element concentrations, pollution indices, and hazard quotients. Subsequently, a discriminant function based on the mitotic index, chromosomal aberrations, and nuclear abnormalities was suitable to classify the samples by crop type. These results demonstrate the sensitivity of Allium cepa L. to the toxicity of complex mixtures in field crops and its potential as an in-situ approach for soil health monitoring in organic and conventional crop systems.

Influence of edaphic and management factors on soils aggregates stability under no-tillage in Mollisols and Vertisols of the Pampa Region, Argentina

In the highly fertile and productive soils of the Pampa Region of Argentina, constraints on soil water regime as a consequence of the decline in aggregates stability and the development of platy structures, are observed. Most of agricultural plots in this region, even under no tillage, are subjected to simplification of crop sequences (low cropping intensity) with predominance of soybean. On the contrary, some farmers are intensifying the crops sequence to avoid soil degradation and equilibrate economical incomes. The aim of this work was to evaluate the effects of intrinsic soil factors and of cropping intensity on aggregates stability in the surface horizon of the main soils in this region. Three Mollisols (an Entic Haplustoll and two Typic Argiudolls) and a Vertisol (Hapludert) located across a west-east transect in the northern part of the Argentinean Pampas were selected for this study. In each site two management treatments under no-till (GAP: Good Agricultural Practices –high cropping intensity- and PAP: Poor Agricultural Practices –low cropping intensity-) and a soil without cultivation as a reference (NE: Natural Environment) were compared. In each treatment, aggregates destruction mechanisms were assessed by Le Bissonnais (1996) tests: slaking, microcraking and cohesion loss. Mollisols showed higher aggregates stability than the Vertisol. Differences on aggregates stability depended on management variables and on organic carbon contents in the Mollisols and on both clay content-clay type in the Vertisol, revealing a strong relationship of aggregation mechanisms with soils taxonomic order. In the Mollisols, the labile coarse particulate organic carbon fraction (POCc) determined the shifts on slaking and overall aggregates stability rather than other carbon fractions. In the soils studied, aggregates stability was linked mainly to management variables, best reflected by the cropping intensity index (CI). More intensive agricultural managements (GAP treatments) in Mollisols and Vertisol, resulted in an enhancement of aggregates stability; however, this relationship was stronger in the Mollisols. Surface horizons from both soil orders evidenced a high soil fragility related to slaking process (FW10s and FW tests). Thus, FW test was the best test to discriminate between management treatments. The results obtained in this work allow, on the one hand, to understand the stabilization mechanisms of the structure in the surface horizon of the main Pampas soils and, on the other hand, to highlight the effect of different NT management practice on soil aggregate stability, which highly affects soil health and the sustainability of agricultural systems.

Earthworm Diversity, Forest Conversion and Agroforestry in Quang Nam Province, Vietnam

The conversion of natural forests to different land uses still occurs in various parts of Southeast Asia with poor records of impact on ecosystem services and biodiversity. We quantified such impacts on earthworm diversity in two communes of Quang Nam province, Vietnam. Both communes are situated within buffer zones of a nature reserve where remaining natural forests are under threat of continued conversion. We identified 25 different earthworm species, out of which 21 were found in natural forests, 15 in agroforestry, 14 in planted forests, and seven each in annual croplands and home gardens. Out of the six species that were omnipresent inhabitants of all observed habitats, Pontoscolex corethrurus largely dominated habitats with intensive anthropogenic activities but was rare in natural forests. Natural and regenerated forests had a much denser earthworm population in the top 10 cm of soil rather than in deeper soil layers. We conclude that the conversion of natural forests into different land uses has reduced earthworm diversity which can substantially affect soil health and ecosystem functions in the two communes. Protection of the remaining natural forests is urgent, while the promotion of a tree-based farming system such as agroforestry can reconcile earthworm conservation and local livelihoods.