Trends in Soil Science Education and Employment

During the last several decades, members of the SSSA have discussed several trends related to soil science education, including: (i) declining academic programs and course offerings at land grant universities, (ii) decreased enrollments, and (iii) improved employment opportunities for soil science graduates (SSSA, 2006; Ferris et al., 2010). The SSSA Advocacy/Education Task Force met in 2007 and concluded that quantitative survey information was needed to document trends in soil science academic programs, student enrollment, faculty, and job opportunities for graduates. Suggested survey topics included: Has the recognition of soil science as a distinct discipline increased or decreased? How has the job market changed during the past decade, and how will job opportunities for soil scientists change in the future? How have undergraduate and graduate soils curricula changed during the last decade? Has enrollment in soil science degree programs and courses changed during the past decade? Has there been a change in the degree programs of students enrolling in soils courses in the past decade? Have soil science programs been combined with other programs? Therefore, the objective of the survey was to quantify trends in student enrollment, faculty positions, pertinent educational issues in soil and related sciences, and career or job opportunities and trends. Expected outcomes included a better understanding of current educational practices and trends, and identification of specific opportunities for SSSA to enhance the practice and profession of soil science

A meta-analysis on biochar's effects on soil water properties – New insights and future research challenges

Biochar can significantly alter water relations in soil and therefore, can play an important part in increasing the resilience of agricultural systems to drought conditions. To enable matching of biochar to soil constraints and application needs, a thorough understanding of the impact of biochar properties on relevant soil parameters is necessary. This meta-analysis of the available literature for the first time quantitatively assess the effect of not just biochar application, but different biochar properties on the full sets of key soil hydraulic parameters, i.e., the available water content (AWC), saturated hydraulic conductivity (Ksat), field capacity (FC), permanent wilting point (PWP) and total porosity (TP). The review shows that biochar increased soil water retention and decreased Ksat in sandy soils and increased Ksat and hence decreased runoff in clayey soils. On average, regardless of soil type, biochar application increased AWC (28.5%), FC (20.4%), PWP (16.7%) and TP (9.1%), while it reduced Ksat (38.7%) and BD (0.8%). Biochar was most effective in improving soil water properties in coarse-textured soils with application rates between 30 and 70 t/ha. The key factors influencing biochar performance were particle size, specific surface area and porosity indicating that both soil-biochar inter-particle and biochar intra-particle pores are important factors. To achieve optimum water relations in sandy soils (>60% sand and <20% clay), biochar with a small particle size (<2 mm) and high specific surface area and porosity should be applied. In clayey soil (>50% clay), <30 t/ha of a high surface area biochar is ideal

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A growth room experiment was conducted to evaluate the bioavailments subject to Canadian guidelines for compost qualability of Cu, Mn, Zn, Ca, Fe, K, Mg, P, S, As, B, Cd, Co, Cr, Hg, Mo, Na, Ni, Pb, and Se from a sandy loam soil amended with sourceity include As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, and quality types are given in According to the National Standard of Canada for compost Half of the basil shoots (aboveground plant material) from quality (Canadian Council of Ministers of the Environment, each treatment were air-dried for extraction of the essential 1996), a compost could be considered mature if it meets two oils. The remaining basil and Swiss chard plants were placed of the following three requirements: (i) C to N ratio of Յ25, in a dryer at 65ЊC for 3 d. (ii) oxygen uptake rate of Յ150 mg O 2 /kg of volatile solids/h, Treatments consisted of 0 (100% soil), 20, 40, and 60% and (iii) germination of cress (Lepidium sativum L.) seeds compost to soil by volume. In other words, we added 175, and radish (Raphanus sativus L.) seeds in compost of Ͼ90% 350, and 525 g of air-dry compost to about 3 kg of soil, resulting of the germination rate of the control sample and a difference in 20, 40, and 60% compost to soil by volume. Constituents in the growing rate between the control sample and the plants of growth medium in greenhouse and container production grown in compost-soil mixture of Ͻ50%. A seed phytotoxicity systems are usually added and/or mixed by volume, but soil test to evaluate compost maturity was conducted by using amendments in field production systems are added on an area cress and marigold (Calendula officinalis L.) seeds and a direct or weight basis. The results from this study are valid for both seed tes

Perennial warm-season grasses for producing biofuel and enhancing soil properties: An alternative to corn residue removal

Removal of corn (Zea mays L.) residues at high rates for biofuel and other off-farm uses may negatively impact soil and the environment in the long term. Biomass removal from perennial warm-season grasses (WSGs) grown in marginally-productive lands could be an alternative to corn residue removal as biofuel feedstocks while controlling water and wind erosion, sequestering carbon (C), cycling water and nutrients, and enhancing other soil ecosystem services. We compared wind and water erosion potential, soil compaction, soil hydraulic properties, soil organic C (SOC), and soil fertility between biomass removal from WSGs and corn residue removal from rainfed no-till continuous corn on a marginally productive site on a silty clay loam in eastern Nebraska after 2 and 3 yr of management. The field-scale treatments were: 1) switchgrass (Panicum virgatum L.), 2) big bluestem (Andropogon gerardii L.), and 3) low-diversity grass mixture [big bluestem, indiangrass (Sorghastrum nutans (L.) Nash), and sideoats grama (Bouteloua curtipendula (Michx.) Torr.)], and 4) 50% corn residue removal with three replications. Across years, corn residue removal increased wind erodible fraction from 41% to 86% and reduced wet aggregate stability from 1.70 to 1.15 mm compared with WSGs in the upper 7.5 cm soil depth. Corn residue removal also reduced water retention by 15% between -33 and -300 kPa potentials and plant available water by 25% in the upper 7.5 cm soil depth. However, corn residue removal did not affect final water infiltration, SOC concentration, soil fertility, and other properties. Overall, corn residue removal increases erosion potential and reduces water retention shortly after removal, suggesting that biomass removal from perennial WSGs is a desirable alternative to corn residue removal for biofuel production and maintenance of soil ecosystem services

Hydraulically versus Hormonally Controlled Root Water Uptake from Partially Wet Root Zones

Drip irrigation may lead to non-uniform distributions of water in the root zone. Models that simulate plant root water uptake and transpiration should account for this spatial variation of root zone water content. In this contribution, we present a detailed mechanistic model that describes and couples water flow through the soil, to and through the plant root system and that resolves flow at the single root scale. The water potentials and water fluxes in the plant are determined by the soil water potentials, the architecture and hydraulic properties of the root system, and by the upper boundary conditions at the shoot or root collar, which could be either a prescribed transpiration flux or leaf water potential. In this concept, the soil-plant system is treated as a purely hydraulic system. However, plant physiologists have investigated and debated the role of plant hormones in the regulation of plant transpiration as a function of root zone water potential. Hormones, which are produced in the root zone as a function of the root water potential, are transported by the transpiration stream to the shoot where they regulate stomatal conductance and transpiration. We implemented hormonal signaling in the model and simulated root water uptake and plant transpiration reduction for different scenarios. In the scenarios, the degree of hormonal control, the wetted fraction of the root zone, and the transpiration rate were varied. The simulated plant transpiration rate could be related to an average root zone soil water potential. For purely hydraulically controlled root water uptake, a linear relation between a maximal possible transpiration rate and the average soil water potential was found. For hormonally controlled root water uptake, rather the ratio of actual to potential transpiration rate is a function of the average soil water potential. This indicates that transpiration reduction occurs whenever a part of the root zone is dry independent of the potential transpiration rate. The water potential in the root zone in the dry part decreases with increasing transpiration rate leading to a larger hormone production. But the higher transpiration stream and dilution compensate the higher hormone production so that the hormone concentration in the shoot is not affected