Soil salinization is considered a type of global-scale soil degradation, whereby excessive salinity severely diminishes soil health, which is primarily manifested through disrupted soil structures ...and reduced fertility. Furthermore, plant growth capacity is inhibited, and productivity is diminished. Consequently, the improvement of saline soils is regarded as a particularly important aspect of enhancing land production. To elucidate the roles of organic amendments and mycorrhizal fungi in the improvement of saline soils, seven treatments were set up, including biochar alone (B), straw alone (S), arbuscular mycorrhizal fungi alone (A), biochar in combination with arbuscular mycorrhizal fungi (BA), straw in combination with arbuscular mycorrhizal fungi (SA), and a control (CK). The results revealed that the seedling height growth rate under the BA treatment was significantly higher than that of the CK by 31.66%. The capillary porosity of the soil under the addition of BA was significantly higher than the CK by 3.17% in the 0–20 cm soil layer. The BA treatment reduced the fractal dimension of soil aggregates considerably by 19.06% in the 0–20 cm soil layer, and 13.71% in the 40–60 cm soil layer in contrast to the CK, respectively. In addition, the positive effects of the BA treatment were significant in the 20–40 cm soil layer. Overall, the application of biochar alone promoted the water stability of soil aggregates. The combination of arbuscular mycorrhizal fungi and biochar promoted plant growth, improved soil pore structures, promoted agglomerate water stability, and led to improved microbial activities. The results showed that organic amendments applied in conjunction with AMF improved the environment of salinized soil, which is a key factor in the promotion of plant growth and the long-term stability of soil health. This study provides a key technical basis for remediation of salinized soil.
Rapid soil testing and soil quality assessment are essential to address soil degradation and low farm incomes in smallholder farms. With the objective of testing diffuse reflectance spectroscopy ...(DRS) to rapidly assess soil chemical properties, nutrient content and a soil quality index (SQI), samples of surface soil were collected from 1113 smallholder farms in seven districts in Bundelkhand region of Uttar Pradesh, India. A minimum dataset (MDS) approach was followed to estimate SQI using the three chemical parameters of soil pH, electrical conductivity (EC) and soil organic carbon (SOC), and 11 different soil nutrients. Principal component and correlation analyses showed that soil pH, SOC content and three available nutrients − copper (Cu), iron (Fe) and sulphur (S) − may constitute the MDS. Estimated SQI values showed strong positive correlation with crop yields. Results of chemometric modelling showed that the DRS approach could yield the coefficient of determination (R2) values in the validation datasets ranging from 0.79 to 0.94 for exchangeable calcium (Ca) followed by 0.67–0.88 for exchangeable potassium (K), 0.52–0.86 for SOC and 0.53–0.81 for available boron (B) content. Except in one district, the DRS approach could be used to estimate SQI values with R2 values in the range of 0.63–0.81; an R2 value of 0.71 was obtained in the pooled dataset. We also estimated the three‐tier soil test crop response (STCR) ratings to compare DRS and wet chemistry soil testing approaches. Similar STCR ratings were obtained for both these approaches in more than 86% of the samples. Parameters for which both the methods yielded similar ratings in more than 80% of the samples were EC (>98%), pH and exchangeable Ca (>81%) and available B (>89%). With similar ratings, these results suggest that the DRS approach may safely be used for farmers' fields, replacing the traditional wet analysis approach of soil testing.
Microbial metabolic products play a vital role in maintaining ecosystem multifunctionality, such as soil physical structure and soil organic carbon (SOC) preservation. Afforestation is an effective ...strategy to restore degraded land. Glomalin‐related soil proteins (GRSP) and amino sugars are regarded as stable microbial‐derived C, and their distribution within soil aggregates affects soil structure stability and SOC sequestration. However, the information about how afforestation affects the microbial contribution to SOC pools within aggregates is poorly understood. We assessed the accumulation and contribution of GRSP and amino sugars within soil aggregates along a restoration chronosequence (Bare land, Eucalyptus exserta plantation, native species mixed forest, and native forest) in tropical coastal terraces. Amino sugars and GRSP concentrations increased, whereas their contributions to the SOC pool decreased along the restoration chronosequence. Although microaggregates harbored greater microbial abundances, amino sugars and GRSP concentrations were not significantly affected by aggregate sizes. Interestingly, the contributions of amino sugars and GRSP to SOC pools decreased with decreasing aggregate size which might be associated with increased accumulation of plant‐derived C. However, the relative change rate of GRSP was consistently greater in all restoration chronosequences than that of amino sugars. The accumulation of GRSP and amino sugars in SOC pools was closely associated with the dynamics of soil fertility and the microbial community. Our findings suggest that GRSP accumulates faster and contributes more to SOC pools during restoration than amino sugars did which was greatly affected by aggregate sizes. Afforestation substantially enhanced soil quality with native forest comprising species sequestering more SOC than the monoculture plantation did. Such information is invaluable for improving our mechanistic understanding of microbial control over SOC preservation during degraded ecosystem restoration. Our findings also show that plantations using arbuscular mycorrhizal plants can be an effective practice to sequester more soil carbon during restoration.
Afforestation of bare land greatly enhanced the accumulation of glomalin‐related soil proteins (GRSP) and amino sugars, but it decreased their contribution to soil organic carbon (SOC). The faster accumulation and greater contribution of GRSP to SOC compared with those of amino sugars highlight the important role of arbuscular mycorrhizal fungi in mediating soil C cycling during forest restoration, despite the proportional contribution of GRSP and amino sugars to the SOC pool diminishing with forest restoration.
Background and aims Soils can act as agents of natural selection, causing differential fitness among genotypes and/or families of the same plant species, especially when soils have extreme physical ...or chemical properties. More subtle changes in soils, such as variation in microbial communities, may also act as agents of selection. We hypothesized that variation in soil properties within a single river drainage can be a selective gradient, driving local adaptation in plants. Methods Using seeds collected from individual genotypes of Populus angustifolia James and soils collected from underneath the same trees, we use a reciprocal transplant design to test whether seedlings would be locally adapted to their parental soil type. Results We found three patterns: 1. Soils from beneath individual genotypes varied in pH, soil texture, nutrient content, microbial biomass and the physiological status of microorganisms. 2. Seedlings grown in local soils experienced 2.5-fold greater survival than seedlings planted in non-local soils. 3. Using a composite of height, number of leaves and leaf area to measure plant growth, seedlings grew ∼17.5% larger in their local soil than in non-local soil. Conclusions These data support the hypothesis that variation in soils across subtle gradients can act as an important selective agent, causing differential fitness and local adaptation in plants.
Purpose
Cereal-based cropping systems under arid and semiarid climates have typically low soil organic matter and fertility, and natural fallowing during summer gap could have negative effects on ...soil quality and health. We tested an alternative approach of using biochar and leguminous cover crops to replace natural summer fallowing of about 75 days in the wheat-maize-wheat cropping systems with a view of studying the effects on legume productivity, soil organic carbon (C), and soil nutrients over the 2-year experiments.
Materials and methods
The two-factor completely randomized block experimental design consisted of biochar, developed from acacia tree biowaste and applied at 0, 5, and 10 t ha
−1
rate, and leguminous cover crops (cowpea, mungbean, and sesbania) with natural fallow were used to test soil fertility and crop productivity. Treatments were laid out following completely randomized block design and each treatment had three replicates leading to 36 experimental plots in total. Pearson’s correlation coefficients were calculated to find the relationships between plant and soil variables. Regression analysis was performed to study correlations of total organic C with soil available N, P, and K contents.
Results and discussion
Results from the 2-year experiment indicated that plant height, pods plant
−1
, grains pod
−1
, 1000-grain weight, fresh and dry biomass, and grain yield were higher at 10 t ha
−1
biochar rate; however, the nodule density plant
−1
of cowpea and sesbania was the highest at 5 t ha
−1
biochar. Integrating legumes with biochar further conserved and improved soil C which significantly positively correlated with soil fertility indicators. Despite linear positive changes in soil pH and electrical conductivity (EC) with biochar rate, increase was minor and was never significant. We observed significant positive relationships of biochar rate with soil organic C contents and soil N and K contents whereas soil P contents were higher at 5 t ha
−1
biochar rate. However, not always significant difference between 5 and 10 t ha
−1
biochar rates for legume and soil productivity suggested flexibility of choosing the biochar application rate.
Conclusions
Our study emphasized that adopting integrative biochar-leguminous cover crop fallowing to replace natural summer fallowing could yield beneficial effects in terms of conserving soil organic carbon, sustaining soil fertility, and improving soil quality. In addition to positive supplementary effects on the succeeding crops, this approach also allows at utilizing and recycling on-farm biowaste more efficiently and environment friendly.
The study investigated the effect of different land use systems on soil physical and chemical properties in Odeda Local Government Area, Ogun State, Nigeria. A total number of nine composite samples ...were collected each from the sampling locations at three depths (0–10, 10–20 and 20–30 cm) using a soil auger from three different locations; abattoir wastewater area, farmland area, and automobile workshop area. Some physicochemical properties that reflect soil nutrients content and fertility status (Ca
2+
, Mg
2+
, Na
+
, K
+
, C, N, P, pH, ECEC, particle size, electrical conductivity, and hydrocarbon content) were determined using standard physicochemical techniques. Results from the oil-spill affected (Automobile workshop) and non-oil affected soil were compared. The result shows that land use type affects soil properties differently; bulk density was low in farmland due to the penetration of roots into the soil, but was high at abattoir because of the abattoir effluent on soil that decomposed and reduced the pore space in the soil. The bulk density also high at the mechanic workshop because of the movement of vehicles which vary from light to heavy. Chemical properties like organic matter were more in mechanic village and abattoir than farmland because of the abattoir effluent, which decomposed to increase the organic matter in the soil and the presence of organic compounds from vehicles at mechanic village increased the level of organic matter in the soil. The organic matter was present in large quantity in the farmland, but was reduced by consumption by the plant.
Abstract Clarifying the distribution and dynamics of soil moisture during the freeze–thaw process is crucial for surface ecology and is an objective requirement to investigate the mechanism of ...changes during the groundwater recharge process in a freeze–thaw zone. Based on the monitoring data of soil moisture and temperature in the Changbai Mountain area, the freeze–thaw process is classified into four periods. This study investigates the hydrothermal migration processes during different periods. The simultaneous heat and water model is used to simulate and analyse the infiltration of soil moisture into groundwater under five precipitation insurance rates. The results are as follows: (1) The smaller the soil depth, the stronger is the correlation between soil temperature and air temperature during the freeze–thaw process. (2) The redistribution of soil moisture before and after freeze–thaw is significantly affected by the soil texture, and soil permeability affects the recharge of soil moisture from the upper region to the lower region during the thawing period. (3) Groundwater receives vertical infiltration recharge mainly during non‐freezing and is supplied by freezing and snowmelt recharge during the stable thawing period. The percentage of soil water infiltration during the stable thawing period in the total annual infiltration increases gradually with the precipitation insurance rate.
The invasive and widespread golden apple snail (GAS,
Pomacea canaliculata
) is a harmful crop pest in many parts of Asia. The heavy use of molluscicides to control GAS could result in soil and water ...pollution as well as in loss of biodiversity. A sustainable and pollution-free control method is urgently needed to counteract this invasion. In this study, we proposed using dried and powdered GAS residue to neutralize and fertilize soils. We compared the effects of adding GAS residue (i.e., ground GAS shell and meat residue) to the effects of adding lime upon soil properties and microbes in a greenhouse pot experiment. Each pot was incubated for 120 days, and soil pH, nutrients, microbial species, and enzyme activity were assessed. Results showed that addition of GAS residue significantly improved soil pH, contents of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), and available nitrogen but decreased soil available phosphorus (AP) content due to phosphorus sorption induced by soil organic matter (OM) and high pH. The GAS residue added to soil released nutrients and alleviated soil acidity, as well as provided more resources to soil microbes to increase their bioactivity, although lime addition was better at mitigating soil acidity. We found that with added GAS residue of 25 g kg
−1
, the soil nitrate nitrogen (NO
3
-N) content increased by 10 times; microbial biomass increased by 43%; and enzyme activity of β-1,4-glucosidase, β-1,4-
N
-acetylglucosaminidase, and β-
d
-cellobiosidase also were enhanced, compared to the control. Our findings suggest that GAS residue functions well as a fertilizer and soil amendment to aid the remediation of barren and acidic soils, making it a valuable and useful option in the control of the invasive GAS.
Crop residues are a potential source of renewable feedstocks for cellulosic ethanol production because of their high cellulose content and easy availability. Indiscriminate removal as biofuel may, ...however, have adverse impacts on soil, environment, and crop production. This article reviews available information on the impacts of crop residue removal on soil properties, crop yields, and soil erosion across a wide range of soils and ecosystems. It explicitly synthesizes data on the independent impacts of crop residue removal on soil and environment rather than on the interrelated tillage-crop-residue management impacts. Published literature shows that residue removal adversely impacts near-surface soil physical, chemical, and biological properties. Unmulched soils are prone to particle detachment, surface sealing, crusting, and compaction. Residue removal reduces input of organic binding agents essential to formation and stability of aggregates. It also closes open-ended biochannels by raindrop impacts and reduces water infiltration, saturated/unsaturated hydraulic conductivity, and air permeability, and thereby increases runoff/soil erosion and transport of non-point source pollutants (e.g., sediment and chemicals). Residue removal accelerates evaporation, increases diurnal fluctuations in soil temperature, and reduces input of organic matter needed to improve the soils' ability to retain water. It reduces macro- (e.g., K, P, N, Ca, and Mg) and micronutrient (e.g., Fe, Mn, B, Zn, and S) pools in the soil by removing nutrient-rich residue materials and by inducing losses of soil organic matter (SOM)-enriched sediments in runoff. Residue removal drastically reduces earthworm population and microbial carbon (C) and nitrogen (N) biomass. It adversely affects agronomic production by altering the dynamics of soil water and temperature regimes. The short-term (<10 yr) data show nevertheless that residue removal may not always degrade soil physical properties and decrease crop yields in the short term depending on the soil type, topography, and fluctuations in annual weather conditions. Sloping and erosion-prone soils are more rapidly and adversely affected by residue removal than those on flat terrains with heavy texture and poorly drained conditions. Sloping terrains are not only highly susceptible to water and wind erosion but also to tillage erosion. In these soils, therefore, a fraction of the total crop residue produced may be available for biofuel production and other expanded uses. Standard guidelines on when, where, and how much residues to remove need to be, however, established. Modeling rates of residue removal are presently based on the needs of soil cover to control erosion without consideration to maintaining SOM and nutrient pools, enhancing soil physical, chemical, and biological quality, and sustaining crop production. Threshold levels of residue removal must be assessed for principal soil types based on the needs to maintain or enhance soil productivity and improve environmental quality. For those soils in which some residues are removed, best management practices (e.g., cover crops, diverse crop rotations, and manure application) must be adopted to minimize adverse impacts of residue removal. Because indiscriminate harvesting of crop residues for biofuel may deteriorate soil properties, reduce crop yields, and degrade the environment, there exists an urgent research need for developing alternative sustainable renewable energy feedstocks (e.g., warm season grasses and short-rotation woody crops).
Biochar has the potential to decrease salinity and nutrient loss of saline soil. We investigated the effects of biochar amendment (0–10 g kg−1) on salinity of saline soil (2.8‰ salt) in NaCl leaching ...and nutrient retention by conducting column leaching experiments. The biochar was produced in situ from Salix fragilis L. via a fire‐water coupled process. The soil columns irrigated with 15 cm of water showed that biochar amendment (4 g kg−1) decreased the concentration Na+ by 25.55% in the first irrigation and to 60.30% for the second irrigation in sandy loam layer over the corresponding control (CK). Meanwhile, the sodium adsorption ratio (SAR) of soil after the first and second irrigation was 1.62 and 0.54, respectively, which were 15.2% and 49.5% lower than CK. The marked increase in saturated hydraulic conductivity (Ks) from 0.15 × 10–5 cm s−1 for CK to 0.39 × 10–5 cm s−1, following 4 g kg−1 of biochar addition, was conducive to salt leaching. Besides, biochar use (4 g kg−1) increased NH4+‐N and Olsen‐P by 63.63% and 62.50% over the CK, but accelerated NO3–‐N leaching. Since 15 cm hydrostatic pressure would result in salt accumulation of root zone, we would recommend using 4 g kg−1 of biochar, 30 cm of water to ease the problem of salt leaching from the surface horizon to the subsoil. This study would provide a guidance to remediate the saline soil in the Yellow River Delta by judicious application of biochar and irrigation.
Coupled effects of biochar use and irrigation on salt leaching of saline soil in the Yellow River Delta.
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