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Sorption is considered one of the most important processes controlling pesticide mobility in agricultural soils. Accurate predictions of sorption coefficients are needed for reliable risk assessments of groundwater contamination from pesticides. In this work, we aim to estimate the glyphosate sorption coefficient, K d , from easily measurable soil properties in two loamy, agricultural fields in Denmark: Estrup and Silstrup. Forty-five soil samples in Estrup and 65 in Silstrup were collected from the surface in a rectangular grid of 15 × 15-m from each field, and selected soil properties and glyphosate sorption coefficients were determined. Multiple linear regression (MLR) analyses were performed using nine geo-referenced soil properties as variables to identify the parameters related with glyphosate sorption. Scenarios considered in the analyses included: (i) each field separately, (ii) both fields together, and (iii) northern and southern sections of the field in Silstrup. Considering correlations with all possible sets of the same nine geo-referenced properties, a best-four set of parameters was identified for each model scenario. The best-four set for the field in Estrup included clay, oxalate-extractable Fe, Olsen P and pH, while the best-four set for Silstrup included clay, OC, Olsen P and EC. When the field in Silstrup was separated in a northern and southern section, the northern section included EC, and oxalate-extractable Fe, Al and P, whereas the southern part included pH, clay, OC and Olsen P. The best-four set for both fields together included clay, sand, pH and EC. Thus, the most common parameters repeated in the best-four sets included clay and pH as also reported previously in the literature, but in general, the composition of the best-four set differed for each scenario, suggesting that different properties control glyphosate sorption in different locations and at different scales of analysis. Better predictions were obtained for the best-four set for the field in Estrup (R 2 = 0.87) and for both fields (R 2 = 0.70), while the field in Silstrup showed a lower predictability (R 2 = 0.36). Possibly, the low predictability for the field in Silstrup originated from opposing gradients in clay and oxalate-extractable Fe across the field. Also, whereas a lower clay content in Estrup may be the limiting variable for glyphosate sorption, the field in Silstrup has a higher clay content not limiting the sorption, but introducing more variability in K d due to changes in other soil properties.

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The mobility of water-dispersible colloids (WDCs) in soil may be influenced by soil management practices such as organic soil amendments. Biochar has recently been promoted as a useful soil amendment, and extensive research has been devoted to investigating its effects on soil macroscopic properties and functions. However, there is limited understanding of the effects of biochar application on micro-scale particle dynamics. We conducted a field study to investigate the effects of the application of birch ( spp.) wood biochar on colloid dispersibility with respect to application rate, history, and physicochemical soil properties. Undisturbed soil cores (100 cm) were collected from the topsoil of two agricultural sites in Denmark with soils of sandy loam texture. The two sites received biochar at different application rates (0-100 Mg ha) and were sampled 7 to 19 mo later. The WDC content was determined using an end-over-end shaking method on 100-cm intact soil cores, and the colloid solution was analyzed for electrical conductivity, pH, and zeta potential. The WDC content increased with biochar application rate because of biochar-induced changes in soil chemistry and was strongly and positively correlated with the concentration of exchangeable monovalent cations in the soils. Biochar application increased pH and decreased electrical conductivity and zeta potential in the colloid suspension more in the short term (7 mo) than in the long term (19 mo). Thus, there is potential for biochar to induce short-term changes in soil solution chemistry in agricultural soils, which may influence the mobility of soil colloids.

Plants are sessile organisms and unlike animals, cannot run away from adverse environmental conditions. Therefore, they have evolved sophisticated signaling and protective systems to overcome sub-lethal stress situations. Although, effect of stress on physiology and morphology were studied earlier, the research on molecular mechanisms of stress response is albeit new. Studies at the molecular level on stress physiology reveal that, many stress-induced pathways converge downstream or interact significantly. Abiotic stress factors regulate the extent and pattern of developmental programme. The timing of transition from vegetative to flowering phase, which is vital for survival and reproductive success, is often altered under various stresses. Unraveling the mechanisms by which different environmental stresses induce their effects and how tolerance to stress is achieved is an active area of research. Enhancing stress tolerance, especially in crop plants is an area of prime importance. In this review, we focus on stress responses induced by temperatures, high and low light intensities, UV radiation, drought and salinity stress and summarize the recent advancements by highlighting the underlying molecular pathways and processes.

Application of biochar to agricultural fields to improve soil quality has increased in popularity in recent years, but limited attention is generally paid to existing field conditions before biochar application. This study examined the short-term physicochemical effects of biochar amendment in an agricultural field in Denmark with a calcium carbonate (CaCO) gradient. The field comprised four reference plots and four plots to which biochar (birch wood pyrolyzed at 500°C) was applied at a rate of 20 t ha. Five undisturbed soil columns (10 cm diam., 8 cm height) were sampled from each plot 7 mo after biochar application, and a series of leaching experiments was conducted. The leachate was analyzed for tritium (used as a tracer), colloids, and phosphorus concentration. The results revealed that the presence of CaCO has resulted in marked changes in soil structure (bulk density) and soil chemical properties (e.g., pH and ionic strength), which significantly affected air and water transport and colloid and phosphorous leaching. In denser soils (bulk density, 1.57-1.69 g cm) preferential flow dominated the transport and caused an enhanced movement of air and water, whereas in less dense soils (bulk density, 1.38-1.52 g cm) matrix flow predominated the transport. Compared with reference soils, biochar-amended soils showed slightly lower air permeability and a shorter travel time for 5% of the applied tracer (tritium) to leach through the soil columns. Colloid and phosphorus leaching was observed to be time dependent in soils with low CaCO. Biochar-amended soils showed higher colloid and P release than reference soils. Field-scale variations in total colloid and P leaching reflected clear effects of changes in pH and ionic strength due to the presence of CaCO. There was a linear relationship between colloid and P concentrations in the leachate, suggesting that colloid-facilitated P leaching was the dominant P transport mechanism.