Conservation agriculture has been marketed to producers as a sustainable way to increase soil productivity and buffer the effects of anticipated fluctuations in both climate and the price of fuel and ...fertilizer. Despite US Farm Bill financial incentives promoting the use of conservation practices such as no-tillage and cover crops among producers, widescale adoption of cover crops in the US remains low. Implementing no-tillage and cover crop use may take years of consistent management to show measurable soil quality improvement. Conversely, costs associated with cover crop planting and management must be incurred immediately and before the accrual of any benefits. Current research has largely focused on the soil quality benefits of cover crops without considering the short-term implementation costs for producers comparing their current production systems to conservation systems they may adopt. To help fill this knowledge gap, soil properties, cash crop yield, and annual production costs were evaluated in a three-year maize /soybean study comparing a conservation system to a conventional production system in Mississippi from 2016 to 2018. The conventional system included frequent tillage and control of winter weeds with a residual soil herbicide (conv. till + bare). We compared five different levels of conservation systems, including a conservation system with no-tillage and cover crops (no-till + cover). We found a lack of consistent improvement in soil properties such as soil organic matter increase or crop yield in the conservation system over the three-year period. The economic benefits of substituting no-tillage and cover crops for expensive conventional inputs were much greater than the modest soil property improvements observed from 2016 to 2018 crops. Though crop yields varied, the cost of cash crop production in the conservation system (no-till + cover) was 43% less than the cost of the conventional system ($29.67 per Mg of crop yield in the conv. till + bare to $17.04 per Mg of crop yield in the no-till + cover system), highlighting a short-term economic incentive for producers to switch to conservation agriculture. The greatest resource benefit from the conservation system was a reduction in estimated soil loss, as mean soil loss in no-till and cover crop decreased by 86% compared to the conventional system (3.5–25.1 t ha-1). These results demonstrate that conservation agriculture has the potential to decrease overall production cost while decreasing the risk of accelerated soil erosion during expected weather extremes associated with climate change, potentially making both farming operations and agroecosystems more resilient.
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•Cover crops and no-tillage did not significantly increase soil organic matter in the short term (3 years).•No-till with cover crops cost less than conventional till left bare.•No-till reduced soil loss more than cover crops.•Cover crops did not fully mitigate soil loss in tilled systems.
The Mississippi River Delta (U.S.A.) is the major agricultural and aquacultural base where many crops and fishes are sensitive to micronutrients (Zn, Cu, Mn). Zinc is a common yield-limiting factor ...for rice and was reported to increase rice yields grown on some Delta soils. Soil/sediments in fish ponds of the Delta are drained and disposed for improving the conditions of bottoms. Bioavailability of micronutrients in soils is controlled by distribution between solution and solid-phase and further among various solid-phase compounds. The effects of land uses on distribution and bioavailability of micronutrients (Cu, Zn, Mn) in Mississippi River Delta have not been studied. The objectives of this study were to determine effects of land uses on solid-phase distribution of micronutrients (Cu, Zn, Mn) and Fe in selected vertisols of the Mississippi River Delta alluvial plain. Land uses include upland forest, rice fields and short- and long-term of catfish production. Micronutrients Cu and Zn and Fe and Mn in fresh soils were fractionated into seven operationally defined solid-phase components. Iron and Zn were mainly present in the stable residual fraction (60–70% of the total Zn and 50–60% of the total Fe), Mn mainly in labile fractions (70–80% of the total Mn, including soluble plus exchangeable, carbonate bound, Mn oxide bound, and organically bound fractions), and Cu in the potentially labile fractions (40–50% of the total Cu in amorphous and crystalline Fe oxide bound fractions). Partitioning of these elements into solid-phase fractions varied with land uses. Mn, Fe and Zn in catfish pond soils were higher in labile fractions and lower in potential labile fractions than paddy and forest soils. Paddy and forest soils had higher Fe, Mn and Zn in potential labile fractions. Drying caused redistribution of metals in solid-phase components with possibably lower potential bioavailability and mobility. In conclusion, land uses strongly affect micronutrient distribution in solid-phase components in the selected vertisols of the Mississippi River Delat alluvial plain. The results of the present study may be applicable to other river delta areas of the world.
The purpose of this study was to quantify the solubility and distribution of As among solid-phase components in poultry wastes and soils receiving long-term poultry waste applications. Arsenic in the ...water-soluble, NaOCl-extractable (organically bound), NH
2OH·HCl-extractable (oxide bound) and residual fractions were quantified in an Upper Coastal Plain soil (Neshoba County, MS) that received annual waste applications. After 25 years, As in the amended soil had a mean of 8.4 mg
kg
−1 compared to 2.68 mg
kg
−1 for a non-amended soil. Arsenic in the amended soil was mainly in the residual fraction (72% of total), which is generally considered the least bioavailable fraction. Arsenic in poultry waste samples was primarily water-soluble (5.3–25.1 mg
kg
−1), representing 36–75% of the total As. To assess the extent of spatial heterogeneity, total As in a 0.5-ha area within the long-term waste-amended field was quantified. Soil surface samples were taken on 10-m grid points and results for total As appeared negatively skewed and approximated a bimodal distribution. Total As in the amended soil was strongly correlated with Fe oxides, clay and hydroxy interlayered vermiculite concentrations, and negatively correlated with Mehlich III-P, mica and quartz contents.
Non-living natural organic matter (NOM) is ubiquitous in the oceans, atmosphere, sediments, and soils, and represents the most abundant organic carbon reserves on earth. However, a large proportion ...is considered to be "molecularly uncharacterized" because the inherent complexity of NOM is problematic when applying conventional analytical techniques. This manuscript presents initial applications of LC-NMR (1H) and LC-SPE-NMR (1H) to the studies of NOM isolated from water and soil. LC-NMR is applied to dissolved natural organic matter (DNOM) collected from freshwater environments, and both LC-NMR and LC-SPE-NMR are applied to an alkaline soil extract. The polar and complex nature of the DNOM samples limits conventional reversed phase separation, which can be partially overcome with the use of an ion pair reagent, although such an approach further complicates the NMR detection. LC-SPE-NMR of the soil alkaline extract was encouraging, and specific components in the mixture could be assigned. This work demonstrates that it is both possible to separate and concentrate specific components in NOM such that NMR detection is possible. As NMR information will be critical in unraveling the novel and/or complex structures in NOM this represents a key analytical hurdle in this area.
New approach to studies of heavy metal redistribution in soil Han, F.X.; Banin, A.; Kingery, W.L. ...
Advances in environmental research : an international journal of research in environmental science, engineering and technology,
10/2003, Volume:
8, Issue:
1
Journal Article
Peer reviewed
The bioavailability and mobility of heavy metals in soils is dependent upon redistribution processes between solution and solid phases and among solid-phase components. This paper reviews the ...definitions and applications of two newly developed parameters, the redistribution index and the reduced partitioning parameter, in quantifying redistribution processes of heavy metals in contaminated soils. The redistribution index depicts the removal/attainment of metal-contaminated soils from/to the fractional distribution pattern characteristic of non-amended soils, while the reduced partitioning parameter quantifies the relative binding intensity of heavy metals in soils. Over time, metal salt-spiked and sludge-amended soils approached the fractional distribution pattern of non-amended soils. The rates of redistribution of metals and their binding intensity in soils were affected by the metal species, loading levels and soil properties. Metals in contaminated soils at low loading levels approach the fractional distribution pattern of non-amended soil more rapidly than those at high loading levels. The sequence order of approach by metals to the fractional distribution pattern of non-amended soil was: Cd>Cu>Ni=Zn>Cr. In both non-amended and contaminated soils, Cr had the highest binding intensity, Cd the lowest, and Cu, Ni and Zn, intermediate values. In addition to our own data, primarily on metal salt-spiked soils, these two indices are also used to evaluate redistribution processes of heavy metals in sewage sludge-amended soils from other published reports.
Sediments recovered from 0 to 27
+ meters below the seafloor (mbsf) of a gas-hydrate and gas-venting active area in the Gulf of Mexico were added to a hydrate growth test cell to determine the ...influence of the organic and inorganic sedimentary components on hydrate induction times and formation rates. Induction times were sixteen times shorter in the presence of sediment from approximately 18 mbsf (relative to sediment from 1 mbsf), and remained stable in the presence of sediment from 18 to 27 mbsf. Formation rates increased by a factor of 2.5 in the presence of sediments from approximately 18 mbsf and decreased somewhat in the presence of sediment from 18 to 27 mbsf. Selected samples (surface, 18 and 27 mbsf) were density fractionated and subjected to bulk elemental and X-ray photoelectron spectroscopy (XPS) analysis. XPS revealed the presence of iron in various chemical environments at depths of 18 and 27 mbsf. High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) was used to characterize the organic component of sediments from selected depths. The discovery of intact proteinaceous material in the surface sediment was surprising due to the labile nature of these biopolymers, and potentially reflects microbial activity in these surface layers. This material was less abundant in sediment from increasing depths, where more lipid-like compounds were prominent. The results suggest that hydrate growth is inhibited by the presence of proteinaceous material but enhanced by lipid-like compounds associated with iron-bearing mineral surfaces.
Diffusion ordered spectroscopy (DOSY) was applied to two extracts of organic matter from the surface horizon of an oak forest soil. It was possible to identify and confirm the presence of numerous ...aliphatic, aromatic, sugar, and amino acid components that could be separated on the basis of diffusion in DMSO-d 6 and D2O. On average, sugar components were identified as the largest molecules in solution, with molecular masses up to ∼1500 Da followed by the aliphatic and aromatic components. Amino acids with a range of molecular weights were also identified in the mixture. The summation of the individual slices from the DOSY experiment closely resembles the conventional 1H spectra of the material, indicating that the components identified with DOSY represent all the components present in the mixture. The separation of components in the mixture in organic solvent supports new findings that fulvic and humic acids are not cross-linked, high molecular weight macromolecules but are instead aggregates composed of relatively simple molecules that take on colloidal properties in the presence of metal ions in aqueous solution. Using the knowledge that these organic mixtures are combinations of relatively simple entities with well-documented reactivities and behavior will improve our ability to predict and model their interactions and fate under natural conditions.
Highly delaminated poly(dicyclopentadiene)/clay nanocomposites were synthesized by in situ polymerization of dicyclopentadiene/organically modified montmorillonite clay dispersions. ...Dicyclopentadiene/clay suspensions were sonicated for various times to enhance the degree of delamination prior to curing. The d spacings of the clay in nanocomposites were monitored using X-ray diffraction (XRD), and the extent of delamination was examined by transmission electron microscopy (TEM) and preliminary neutron scattering studies. A new approach, use of confocal laser microscopy, was employed to follow the dispersion of clay layers, tagged by a fluorescent dye, within the liquid monomer. It is evident that XRD cannot be used alone as a criterion for exfoliation. TEM showed that increasing the clay concentration at constant sonication gave an increase in average tactoid size. The largest improvement in composite mechanical properties occurred at clay loading levels (0.5−1 wt %). Significant increases in T g, elastic bending moduli, flexural moduli, and flexural strengths were found at 0.5−1 wt % clay loadings, where the highest degree of delamination/exfoliation also occurred.
Land application of poultry litter provides essential nutrients for hybrid bermudagrass Cynodon dactylon (L.) Pers. production, but ammonia (NH3) volatilization and N mineralization influence the ...amount of litter N available for plant uptake. Our objective was to determine the combination of broiler litter and fertilizer N, which maximizes the yields of forage and N, P, and K by 'Coastal' bermudagrass. Studies were conducted for 3 yr (1999-2001) in pastures at Newton and Mize, MS that differed widely in soil test P (STP) due to history of litter application (0 vs. 30+ yr, respectively.). Litter rates of 0, 4.5, 8.9, 13.4, and 17.9 Mg ha-1 were obtained by up to four monthly (April-July) applications of 4.5 Mg ha-1 and were supplemented with ammonium nitrate (NH4-NO3) to provide the same total N in each treatment. At Newton, combining litter with fertilizer N increased forage yield by 10% in 1999, 25% in 2000, and 34% in 2001, as compared to fertilizer N. At Mize, K uptake increased as litter rate increased in 2001 only. These responses to litter were related to increased soil P and K at Newton, and increased soil N, P, and Ca at Mize. Averaged across years, maximum P uptake of about 40 kg ha-1 was obtained by applying 8.9 Mg litter + 134 kg N ha-1 at Newton and 4.5 Mg litter + 202 kg N ha-1 at Mize. Safe and effective management of major plant nutrients in broiler litter may require the use of commercial N fertilizer.
ABSTRACT
Copper sulfate (CuSO4) is applied periodically to commercial channel catfish (Ictalurus punctatus) ponds as an algicide or parasiticide. Current understanding of the chemistry of copper in ...soil–water systems suggests that copper may accumulate in pond sediments, although the forms and potential bioavailability of copper in catfish pond sediments are not known. This study investigated the accumulation and distribution of copper in the sediment of catfish ponds receiving periodic additions of CuSO4 · 5H2O. All ponds were constructed in Sharkey (very‐fine, smectitic, thermic Chromic Epiaquert) soil. Nine 0.40‐ha ponds received 59 applications of 2.27 kg CuSO4 · 5H2O per application per pond over 3 yr; no CuSO4 · 5H2O applications were made to nine additional ponds. Total Cu concentration in the sediments of CuSO4 · 5H2O‐amended catfish ponds (172.5 mg kg−1) was four to five times higher than that in the sediments of nonamended ponds (36.1 mg kg−1). Copper accumulated in catfish pond sediments at a rate of 41 μg kg−1 dry sediment for each 1 kg ha−1 of CuSO4 · 5H2O applied to ponds. Copper in the sediments of amended ponds was mainly in the organic matter–bound (30.7%), carbonate‐bound (31.8%), and amorphous iron oxide–bound (22.1%) fractions with a considerable fraction (3.4%; 3 to 8 mg kg−1) in soluble and exchangeable fractions. This indicates that Cu accumulates differentially in various fractions, with proportionally greater initial accumulation in potentially bioavailable forms. However, toxicity bioassays with amphipods (Hyallela azteca) and common cattail (Typha latifolia L.) indicated that the effect of exposure to amended or nonamended pond sediments was not different.
