Low Soil Organic Matter Research Articles

How variable characteristics of bean cropping systems affect Fusarium and Rhizoctonia root rot epidemics?

Fusarium root rot (FRR) and Rhizoctonia root rot (RRR) are potential threats to bean production worldwide. Disease incidence, severity and index, and yield were assessed at vegetative, flowering–podding and maturity stages in 122 commercial bean fields. Area under the disease progress curve (AUDPC), linear and quadratic coefficients of disease-time regressions were also used as epidemiological descriptors. From factor analysis, development of FRR and RRR epidemics were characterized mainly by AUDPC. Using redundancy analysis, 30 agricultural indicators accounted for 69% variations in FRR- and RRR–AUDPC, and bean production. Severe FRR and RRR epidemics and less pod and seed production corresponded with deep seeding, dense weed, low soil organic matter, planting White bean, mechanical cultivation, planting in Abhar region, frequent irrigation, growing continuous bean, lack of herbicide application, fungicidal treatment of soil, urea application, flat seedbed, short initial-drought period, unfertilized planting and early planting. Such epidemiological information assists with improving disease control programs.

Rice–wheat cropping systems in South Asia: issues, options and opportunities

The rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system is the largest agricultural production system worldwide, and is practised on 24 Mha in Asia. Many factors have threatened the long-term sustainability of conventional rice–wheat cropping systems, including degradation of soil health, water scarcity, labour/energy crises, nutrient imbalances, low soil organic matter contents, complex weed and insect flora, the emergence of herbicide-resistant weeds, and greenhouse-gas emissions. Options for improving the yield and sustainability of the rice–wheat cropping system include the use of resource-conservation technologies such as no-till wheat, laser-assisted land levelling, and direct-seeded aerobic rice. However, these technologies are site- and situation-specific; for example, direct-seeded aerobic rice is successful on heavy-textured soils but not sandy soils. Other useful strategies include seed priming, carbon trading and payment, the inclusion of legumes, and eco-friendly and biological methods of weed control. Irrigation based on soil matric potential using tensiometers can be useful for saving surplus water in direct-seeded, aerobic rice. These options and strategies will contribute to resolving water scarcity, saving labour and energy resources, reducing greenhouse-gas emissions, increasing soil organic matter contents, and improving the soil-quality index. Seed priming with various substances that supplement osmotic pressure (osmotica) is a viable option for addressing poor stand establishment in conservation rice–wheat cropping systems and for increasing crop yields. To strengthen the campaign for using resource-conservation technologies in rice–wheat cropping systems, carbon-payment schemes could be introduced and machinery should be offered at affordable prices. The persistent issue of burning crop residues could be resolved by incorporating these residues into biogas/ethanol and biochar production. Because rice and wheat are staple foods in South Asia, agronomic biofortification is a useful option for enhancing micronutrient contents in grains to help to reduce malnutrition.

Organic fertilizer, but not heavy liming, enhances banana biomass, increases soil organic carbon and modifies soil microbiota

Low soil pH and low soil organic matter content are major factors limiting banana production in acid soils. A pot experiment was conducted to determine whether liming or organic fertilizer is effective in mediating banana growth and soil health. The experiment comprised an unamended control and two treatments, lime and OF (organic fertilizer) and sampling was conducted twice, 65 and 280 days after planting. Soil nutrient concentrations, soil microbial communities and enzyme activities, and banana biomass and nutrient uptake were determined. As expected, the application of lime or organic fertilizer significantly increased soil pH and mineral nutrient concentrations and decreased Al3+ concentration. At both harvests an increase in bacterial and fungal diversity in the lime treatment and a shift in the soil bacterial and fungal communities did not translate into increased plant biomass. Organic fertilizer application significantly increased soil organic carbon content and enzyme activities, root length density down the soil profile, plant biomass and nutrient uptake compared to the lime treatment and the control. Changes in the soil microbial community in the organic fertilizer treatment compared to the control followed the same direction as in the lime treatment. However, the relative abundances of Actinobacteria and Ascomycota increased significantly 280 days after planting and potential pathogenic fungi including Fusarium decreased. Our results indicate that heavy liming alone may not be a viable approach to overcome the growth limiting factors in banana production on acid soils. In addition to the increased soil organic matter and nutrient availability, organic fertilizer may prime microbial activities and act as biologically active agent and/or enhance synergistic interactions within the soil microbiome in enhancing plant biomass. Increased soil biological activities after organic fertilizer application emphasize the importance of soil health in promoting the yield of banana crops.

Impacts of over-seeding bermudagrass pasture with multispecies cover crops on soil water availability, microbiology, and nutrient status in North Texas

Cover crops over-sown into established perennial bermudagrass (Cynodon dactylon) pastures has been effective in improving forage productivity and net farm profitability in wetter grasslands in US. To assess if the use of cover crops can do so in the relatively dry regions of Southern Great Plains of Texas, we evaluated what positive and negative impacts accrue from sowing winter growing mixed species cover crops into bermudagrass pastures by measuring soil water dynamics, soil nutrient and soil microbial dynamics on three separate commercial farms over three growing seasons. There was no evidence that annual, winter growing cover crops reduced soil moisture to negatively affect the following production of the bermudagrass pasture. This result was obtained in years that had average to above average precipitation and may have been different in drier years. At one of the farm sites the key biological function changes we measured positive changes in soil biological activity and fertility to indicate that positive biological changes had taken place and could after more years add up to greater improved outcomes. However, the lack of positive soil biological responses on the other two farms may indicate that soils initially having low soil organic matter, poor permeability, water holding capacity and fertility would need to develop greater levels of soil organic matter with better management before positive responses using cover crops would yield acceptable improvements. However, they are a likely means of contributing to these desired improvements. Cover crop biomass levels were greater on the drill than Broadcast and Control but the improved biomass with broadcasting to establish the cover crops on all three farm sites has important cost lowering implications even though it was applied at a 33% higher seeding rate. It is likely that improved grazing management of perennial pasture is necessary to improve soil organic carbon and soil biological function in conjunction with the use of cover crops.

Effect of Organic Waste and Humic Acid on Some Growth Parameters and Nutrient Concentration of Pistachio Seedlings

ABSTRACTPistachio crops in Iran are grown in soil with low soil organic matter. Therefore, a field experiment was conducted at Izadyaran Company, Sirjan, Iran to study the effects of municipal solid waste compost (MSWC), cow manure, and methods of humic acid application (soil and foliar) on growth parameters and nutrients concentration of pistachio seedlings in a complete randomized design with six replications for two years (2011–2013). Results showed that cow manure decreased the leakage percent and maximum leaf number and leaf surface area were obtained in MSWC with foliar application of humic acid and cow manure without humic acid, respectively. The highest chlorophyll b and carotenoid were observed in the second year with cow manure treatment whereas foliar application of humic acid increased total chlorophyll. Calcium (Ca) and iron (Fe) decreased in the second year. At the first year Cow manure application increased phosphorus (P) and manganese (Mn) but in the second year increased magnesium (Mg) concentration. MSWC at the first year increased copper (Cu) and zinc (Zn) concentration. Cow manure and foliar application of humic acid increased the Nitrogen (N) concentration in the first year. These results may have implications for pistachio production in arid and semi-arid soils.

Alternative Sources of Soil Organic Amendments for Sustaining Soil Health and Crop Productivity in India – Impacts, Potential Availability, Constraints and Future Strategies

Among the several causes, critical low soil organic matter status is predominant for decline in soil health and consequent fall in crop productivity. Over the years, availability of traditional source of soil organic amendment, viz. cattle manure drastically declined due to various reasons (domestic uses as fuel and plastering of the kachha houses). The present study highlights that there are many alternative sources of soil organic amendments available in the country which have tremendous potential to improve soil organic matter status and crop productivity, and rejuvenate and enhance the dying total factor productivity of Indian soils. Data from various sources reveal that about 300 million tonnes of alternative sources of soil organic amendments are available in the country. This study highlights that the application of alternative sources of organic amendments directly or indirectly improves soil health by influencing many soil properties (physical and chemical) and enzyme activities (biological) that regulate nutrient dynamics in the soil. Consequent upon improvement in soil environment, the application of alternative sources of soil organic amendments alone or along with recommended dose of fertilizers registered significantly higher yield in different crops across different agro-climatic conditions of the country. Composting and vermicomposting are the best strategies to convert the biomass of available alternative sources of organic amendments to plant nutrient-rich products.

Relationship Between Soil Properties and Nitrogen Mineralization in Undisturbed Soil Cores from California Agroecosystems

ABSTRACTSoil nitrogen (N) mineralization rates from different agricultural regions in California were determined and related to soil properties. Undisturbed soil cores were sampled in spring from 57 fields under annual crop rotations and incubated at 25℃ for 10 weeks. Soil properties varied across and within regions, most notably those related to soil organic matter (SOM), with total soil carbon ranging from 6 to 198 g kg−1. Multivariate linear regression was used to select soil properties that best predicted N mineralization rates. Regression models with a good fit differed between soils with high and low SOM contents, but generally included a measure of SOM quantity, its quality as well as soil texture or mineralogy. Adjusted R2 values were 0.95 and 0.60 for high and low SOM soils, respectively. This study has shown that information on soil properties can contribute to better estimates of N mineralization in soils of contrasting characteristics.

Performance of Sesame (Sesamum indicum L.) as Influenced by 2,4 – Dichlorophenoxyacetic Acid and NPK Fertilizer

Abstract The Guinea savannah zone of Nigeria is beset by increasing population and infrastructural development, thereby putting pressure on available land with rapidly declining fertility due to low organic matter content, soil erosion, high temperature and seasonal bush burning. Sesame is cultivated in this zone and the yield has remained very low, compared to yield in other parts of the world. This could be attributed to poor nutrient status and poor cultural practices used by peasant farmers. A field experiment was conducted at the Teaching and Research Farm, University of Ilorin, Nigeria, in a southern Guinea savannah zone in 2015 and repeated in 2016 cropping season to determine the effects of 2,4-Dichlorophenoxyacetic acid (2,4-D), a plant growth regulator and NPK fertilizer on the growth and yield of sesame. The experiment was laid out as a factorial arrangement, fitted into a randomized complete block design replicated thrice. The factors imposed were 2,4-D (0, 5 and 10 ppm ha−1) and NPK 15:15:15 (0, 100, 200 and 300 kg ha−1). Data were collected on vegetative traits (plant height, number of leaves, leaf area) and yield components (number of capsules per plant; yield per plant and per hectare). The data were subjected to analysis of variance (ANOVA) using the Genstat statistical package 17th edition and significant means were separated by using the least significant difference at 5% level of probability. The result revealed that using plant growth regulator and NPK fertilizer had significant effects (p<0.05) on plant height (151 cm) and yield per hectare (530 kg/ha). The qualitative and quantitative analysis of the seeds further reaffirmed the presence of bioactive compounds, such as saponins, tannins, flavonoids and phenolic compounds, which are important health promoting food in the seeds.

Mechanisms of Interaction between Persulfate and Soil Constituents: Activation, Free Radical Formation, Conversion, and Identification.

Persulfate-based in situ chemical oxidation (ISCO) for soil remediation has received great attention in recent years. However, the mechanisms of interaction between persulfate (PS) and soil constituents are not fully understood. In this study, PS decomposition, activation, free radical formation and conversion processes in 10 different soils were examined. The results showed that soil organic matter (SOM) was the dominant factor affecting PS decomposition in soil, but Fe/Mn-oxides were mainly responsible for PS decomposition when SOM was removed. Electron paramagnetic resonance (EPR) spectroscopy analysis showed that sulfate radicals (SO4•-) and hydroxyl radicals (•OH) generated from PS decomposition subsequently react with SOM to produce alkyl-like radicals (R•), and this process is dependent on SOM content. R• and SO4•-/•OH radicals predominated in soil with high and low SOM, respectively, and all three radicals coexist in soil with medium SOM. Chemical probe analysis further identified the types of radicals, and R• can reductively degrade hexachloroethane in high SOM soil, while SO4•- and •OH oxidatively degrade phenol in low SOM soil. These findings provide valuable information for PS-ISCO, and new insight into the role of SOM in the remediation of contaminated soil.

English

Biochar incorporation as a soil amendment has been shown to enhance soil quality. However, there has been conflicting reports on its short term effects on C and N mineralization and microbial biomass. An incubation experiment was conducted to determine the effects of three different levels (0.5, 1 and 2%) of biochar on carbon mineralization, soil organic carbon, nitrogen mineralization, microbial biomass and total nitrogen from mollisols of two different organic matter (high organic matter soil and low organic matter soil) levels. The experiment consisted of four treatments (Soil, Soil + 0.5% biochar, Soil + 1% biochar and Soil + 2% biochar) and each was replicated three times. Overall, soil respiration rate was reduced by biochar additions over a 100-day period. Two percent biochar application rate showed greatest CO2-C reduction. Soil respiration in high organic matter soil was higher than low organic matter soil. NO3--N level was reduced by biochar addition in both high and low organic matter soils. Control (Soil) of the high organic matter soil showed the highest NO3--N (33.79 mg kg-1) and NH4+-N (7.23 mg kg-1) values at 70 days. The total nitrogen was increased by biochar additions; 1 and 2% application rates showed the highest total nitrogen values. Biochar additions also increased soil microbial biomass carbon and soil microbial biomass nitrogen of both soils. Key words: Biochar, C mineralization, N mineralization, microbial biomass.

The impact of anthropogenically induced degradation on the vegetation and biochemistry of South African palmiet wetlands

There are many different anthropogenic causes of wetland degradation, such as disturbances which affect the physical structure of wetlands, resulting in erosion (altered fire regimes, road and railway building through wetlands, channelization of wetlands), pollution, land-cover change, and climate change. These different types of degradation have various impacts, depending on the type of wetland, soils, biochemistry and other factors. We researched a poorly-studied South African valley-bottom peatland that is dominated by the ecosystem engineer Palmiet: Prionium serratum. We ask the question: what is the impact of degradation by gully erosion, pollution and alien tree invasion on biochemistry and plant community composition of palmiet wetlands? In 39 plots from three palmiet wetlands situated approximately 200 km apart we found that channel erosion, through a loss of alluvium, has probably resulted in leached soils with lower soil organic matter and water content, less able to retain nutrients and cations. Soil leaching is a possible explanation for the groundwater of degraded wetlands having higher electrical conductivity and pH than that of pristine wetlands and a lower soil cation exchange capacity (21.3 ± 5.80–7.7 ± 4.91 meq/100 g). The loss of alluvium typically resulted in a completely new plant community, composed mostly of pioneer species and several alien species. The increase in base saturation (17.5 ± 8.46–30.2 ± 17.85%) and soil pH (4.8 ± 0.51–5.1 ± 0.50) with degradation was hypothesized to be the result of liming practices. Once extremely degraded, i.e. all the alluvium is lost, it is unlikely that these sensitive palmiet wetlands will recover original vegetation communities and lost functions, except on long timescales. We recommend conservation of the few pristine wetlands that remain, and rehabilitation of those that still retain some of their original function.

Assessment of Soil Fertility under Different Land-Use Systems in Dhading District of Nepal

Unscientific land use and cropping techniques have led high soil erosion and degradation of soil quality in the mid-hills of Nepal. To understand the effects of land use systems for selected soil chemical properties in mid-hills, composite soil samples at 0 cm to 20 cm depth were collected from five different land-use systems: Grassland, forest land, upland, lowland, and vegetable farms from Dhading district of Nepal in 2017. Soil samples were analyzed for soil fertility parameters: Soil pH, organic matter (OM), total nitrogen (N), available phosphorus (P), available potassium (K) and its effect due to different land use systems were compared. Results showed that soil pH was neutral in vegetable farms (6.61), whereas the rest of the land-use systems had acidic soils. Soil OM (3.55%) and N (0.18%) content was significantly higher in forest, but the lowest soil OM (1.26%) and N (0.06%) contents were recorded from upland and lowland farms, respectively. Available P was the highest in the vegetable farm (41.07 mg kg−1) and was the lowest in grazing land (2.89 mg kg−1). The upland farm had significantly higher P levels (39.89 mg kg−1) than the lowland farm (9.02 mg kg−1). Available K was the highest in the vegetable farm (130.2 mg kg−1) and lowest in grazing land (36.8 mg kg−1). These results indicated that the land under traditional mixed cereal-based farming had poor soil health compared with adjacent vegetable, grazing, and forest lands among the study area. The variations in soil fertility parameters suggest the immediate need for improvement in soil health of traditional farmlands.

Soil infiltration rate of forestland and grassland over different vegetation restoration periods at Loess Plateau in northern hilly areas of China

Vegetation restoration practices play an important role in environmental management and could mitigate soil and water losses in the Chinese Loess Plateau. The main objective of this study was to ascertain the influence of vegetation durations on soil infiltration rate and other related soil properties. Undisturbed soil columns in triplicate from the same plot, with different locations, were collected to estimate the accumulated soil infiltration over different vegetation periods (9, 15, and 25 years) of grassland and forestland at different time intervals. The highest cumulative infiltration and wet front movement speed was recorded after 25 years of grassland and increased with the vegetation restoration duration. Low root biomass density (g cm−3) and soil organic matter (g kg−1) were recorded in the 9-year plantation of forestland and grassland; however, maximum root biomass densities of 1.614 ± 0.95 mg cm−3 and 0.938 ± 0.03 mg cm−3 were recorded after 25 years of forestland and grassland. Furthermore, root images scanner analysis showed that the 25 years of grassland has higher root length density and root surface area density of 5.917 ± 0.86 cm cm−3 and 2.058 ± 0.95 cm2 cm−3 at surface and subsurface soil layers. We therefore suggest that for revegetation periods of less than 25 years, grassland would be better for soil infiltration and related soil properties particularly in areas of the Chinese Loess Plateau.

Biochar's impact on dissolved organic matter (DOM) export from a cropland soil during natural rainfalls

Although biochar amendment to soil has achieved widely recognized benefits such as plant growth improvement and carbon sequestration, what impact it would have on soil carbon cycling, especially on the behavior of the active dissolved organic matter (DOM), is still unclear. This study evaluated biochar's effects on soil properties and the characteristics of DOM exporting from a cropland Entisol. The soil is the major arable land resource in the upper reaches of the Yangtze River, China and noted for its low soil organic matter and prevalence of preferential flow. Surface runoff, soil pore water and leachate were collected from the field upon a series of natural rainfall. Concentration of dissolved organic carbon (DOC) of soil pore water was found to respond strongly toward the rainfalls. Biochar application led to relatively higher DOC levels within the soil (p > 0.05). Despite apparent increase of DOC and EEM intensities for the freshly-amended soil, PARAFAC analyses indicated no changes in DOM's fluorophore compositions after two years of ageing. The identified DOM components (C1 and C2) showed similar dynamics with the DOCs in responding to the rainfalls. On the other hand, total flux of DOM leaching from biochar-amended plots during three monitored storms was on average 59% higher than the control (p > 0.05), whereas DOM export via surface runoff was slightly diminished. Noticeably, biochar amendment had caused a significant increase of >1000 μm macropores and thus the enhanced infiltration of soil water. Such changes led to increased flow discharge, which in turn resulted in elevated leaching of organic carbon during rainfalls. The results therefore implies that changes of soil structure and hydraulic properties that will take place after biochar application merits attention as they may play a continuous role in influencing the transport of DOM and possibly other solutes via runoff processes.

Above and belowground biodiversity in adjacent and distinct serpentine soils

In this study we analysed the diversity of vascular plants, soil microorganisms and microarthropods on two serpentine outcrops in the Northern Apennines (Italy). The soils of the two sites are at different stages of evolution, as shown by soil depth and soil organic matter (SOM) content: the first site is a serpentine grassland clearing within sub-montane vegetation, while the second is a serpentinite scree rich in specialised flora only, including rare hyperaccumulator plant species such as Noccaea caerulescens and Alyssum bertolonii. The aboveground biodiversity was analysed via floristic relevés. The bacterial diversity was estimated through 16S rDNA profiling of the Ni hyperaccumulator N. caerulescens at the rhizosphere level, which thrives in both sites. Microarthropod communities were characterized by extracting and identifying organisms from the soil. The number of individuals per taxon, Acari/Collembola ratio, biodiversity indices and QBS-ar index were calculated. The two sites showed a clear difference as regards plant community: only three plant species were present in both sites, namely Euphorbia cyparissias, belonging to Euphorbiaceae, Galium spp., belonging to Rubiaceae, and N. caerulescens, belonging to Brassicaeae. Belowground diversity was positively correlated with vegetation cover and SOM content. In particular, among the bacteria colonising the rhizosphere of N. caerulescens (present in both sites), Actinobacteria, which exhibit K-strategist attributes and are more successful in resource-limited, crowded environments, appeared to be more abundant in the site with lower SOM and higher content of Ni. Bacterioidetes, which are specialised in degradation of cellulose, chitin and plant detritus, were instead more abundant in the site with higher SOM. As for soil microarthropod communities, the site with higher concentration and bioavailability of heavy metals and lower SOM showed poorer and less structured community. In conclusion, the data observed with plant, microbial and microarhropod communities identify different micro-habitats, in spite of proximal geographical position and the common metal-rich substrate.

Effects of fertilizer and irrigation management on nitrous oxide emission from cotton fields in an extremely arid region of northwestern China

Nitrogen application as synthetic fertilizer and/or animal manure and method of irrigation are critical management practices affecting crop production and nitrous oxide (N2O) emission in irrigated agriculture systems. A field experiment was conducted in 2015 and 2016 to compare the effects of conventional urea (Urea), animal manure (Manure) and a 50/50 mix of urea and manure (U + M) on N2O emission from flood- or drip-irrigated cotton (Gossypium hirsutum L.) grown on a sandy soil in arid region of northwestern China. Results showed that Manure increased cumulative N2O emission (ƩN2O), applied available N-scaled emission factor (EF) and yield-scaled emission intensity (EI) by 30–188% compared with Urea and U + M, under both irrigation methods. The ƩN2O and EF were not affected by irrigation method in 2015, but were 18–25% greater in the drip- than flood- irrigation in 2016. Cotton yield and N uptake were generally increased by fertilizer or manure additions compared to the unfertilized control, but there were no significant differences between the three fertilized treatments. The overall N2O emission and EF at the study site ranged between 72–506 g N2O-N ha−1 and 0.04-0.15%, respectively, being generally lower than those of other climate zones, probably due to the low available soil moisture and low soil organic carbon which restricted N2O production. Greater N2O emission with manure application was mainly attributed to the increased rates of nitrification and denitrification through the manure’s increased supply of carbon for associated microbes. These results suggest a potential risk of manure application to increase N2O emission for irrigated crop production in soils with low soil organic matter and under dry climate. Further studies are needed for understanding of the linkage between manure-induced N2O emission and activities of associated microbes.

Fine-Root Responses of Populus tomentosa Forests to Stand Density

Stand density directly affects the distribution of ecological factors such as light, heat, and water in forest communities and changes the diversity and structure of undergrowth species, thereby affecting soil health. Fine roots can provide water and nutrients to plants rapidly in the fierce competition of soil resources, so as to get rid of environmental factors. This study examined the fine-root responses of the Populus tomentosa clone S86 to three stand densities (plant × row spacing: 2 × 2 m, 4 × 3 m, 4 × 5 m). We measured the biomass, morphology, and nitrogen content of lower- (1–3 order) and higher-order (>3 order) fine roots, and analyzed soil chemical properties in 10–30 cm. The soil from the density (2 × 2 m) stands showed lower soil organic matter content, available nitrogen, available phosphorous, and available potassium than others. Obviously, lower and higher-order fine roots were different: biomass of the >3 order accounted for 77–87% of the total biomass, 1–3-order fine-root diameter around 0.28–0.38 mm, while >3-order fine root were 1.28–1.69 mm; the length of 1–3-order fine root was longer than the >3 order, and root length density, specific root length, and nutrient content between the 1–3 and >3 orders were different. At 2 × 2 m, 1–3-order fine-root biomass was the highest, 132.5 g/m3, and the 1–3-order fine-root length, diameter, surface, root length density was also the highest; at the same time, the 1–3-order fine-root total nitrogen and organic matter content was also the highest, while the >3 order was highest under 4 × 3 m or 4 × 5 m. The findings of this study show that stand density affected the available nutrient content of the soil. When soil resources were poor, the biomass, morphology, and chemical content of fine roots were adjusted to increase the nutrient absorption rate, particularly in the lower-order roots.

Potential ecological risks of metal(loid)s in riverine floodplain soils

The quality of soils under different land uses is getting deteriorated throughout the world due to various anthropogenic activities. This deterioration is highly complex in riverine floodplain areas due to contamination by multiple point and non-point sources and change in seasons. Therefore, a study was conducted to analyze seasonal (pre and post-monsoon) variations in physico-chemical characteristics, contents of metal(loid)s (Al, As, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sb and Zn) in riverine floodplain soils under three land uses (agricultural, riverbank and roadside) from areas around the rivers Beas and Sutlej in Punjab, India. Further, analysis was done to assess the ecological and genotoxic risks (Allium cepa genotoxicity assay) posed by metal(loid)s in these soils. It was observed that soil samples under the three land uses were slightly alkaline (pre-monsoon) to acidic (post-monsoon) in nature with sandy texture and low soil organic matter. The levels of most metal(loid)s increased in post-monsoon soil samples under the three land uses, which was attributed to increase in soil organic matter, silt and clay contents in post-monsoon samples due to precipitation, flooding and sedimentation. The ecological Risk Index (58.3–104.5) and Modified Risk Index (145.2–178.9) calculated to analyze the level of ecological risks of metal(loid)s revealed that As, Cd and Sb posed moderate to considerable ecological risks in the agricultural and roadside soils in both seasons. Allium cepa genotoxicity assay indicated that the metal(loid)s in studied soils can cause genotoxic effects in biological systems. Therefore, various steps such as reduction in use of agrochemicals, promotion of organic agricultural methods and decontamination of soils using techniques such as phytoremediation etc must be taken to ensure reduction and containment of metal(loid)s in such riverine floodplain areas.

The Frequent Effects of Hydroxyl Radicals on the Oxidation of Crude Oil in Soil

The characteristics of hydroxyl radicals (•OH) frequently produced in the Fenton process and the effects of these radicals on the oxidation of hydrophobic total petroleum hydrocarbons (TPH) in soil are investigated. Twelve groups of Fenton oxidation experiments are conducted using two kinds of crude‐oil‐contaminated soil samples (S1 and S2) with different soil organic matter (SOM) contents. The results show that the decrease of TPH increases by 6774 mg kg−1 (S1) and 5875 mg kg−1 (S2) by using the frequent •OH (•OHf). These results are two times the results obtained by using the single •OH (•OHs) (S1: 3410 mg kg−1, S2: 2918 mg kg−1). The decrease of hydrophobic long‐chain alkanes C21–C30 is greatly improved by using the •OHf, that is, oxidation of 1557–3011 mg kg−1 in soil S1 and 1371–2532 mg kg−1 in soil S2. Moreover, the C21–C30 alkanes in soil S1 with low SOM (3.89%) are more degraded after oxidation. The residual non‐aqueous phase liquid (NAPL) TPH content by using the •OHf (266–1200 mg kg−1) is much lower than that by using the •OHs (2519–4070 mg kg−1). The residual of the NAPL TPH by using the •OHf is 11–29% of the residual by using the •OHs. This result indicates that residual NAPL TPH is reduced by using the •OHf, and the TPH contents in the two soil samples are efficiently oxidized.

Mitigation of soil loss from turfgrass cultivation by utilizing poultry abattoir sludge compost and biochar on low-organic matter soil

ABSTRACTCommercial turfgrass cultivation is one of the main ornamental industries world-wide; however, successive turfgrass sod cutting from the same site removes surface soil, leading to a decline in soil organic matter, impairment of soil fertility and degradation of environment. The present study was aimed to investigate the applicability of poultry abattoir sludge compost (PASC) and biochar (BC) on the establishment of turfgrass by evaluating plant growth performance and mitigation of soil loss by organic waste amendments. The experimental study was designed on the soil which had originally low-organic matter content and previously used as a turfgrass sod harvested site in a sandy loam soil. Incorporation of PASC to soil improved the physicochemical properties in terms of bulk density (BD), water holding capacity (WHC), cation exchange capacity (CEC), pH, total nitrogen, total organic carbon (TOC), and organic matter (OM) by 37 (±2)%, 45 (±3)%, 55 (±3)%, 21 (±2)%, 48 (±2)%, 90 (±10)%, and 96 (±4)%, respectively. PASC-amended treatments enhanced the turfgrass growth rate more than the BC due to its increased nutrient availability. Incorporation of 100 Mg ha–1 (mega gram per hectare) PASC in surface soil with or without BC decreased the mineral soil removal rate by half of the respective soil (control) treatments. The results of the present study confirmed the utilization of PASC and BC as promising agro-industrial-based fertilizers in turfgrass sod production for sustainable soil and nutrient management.