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A theory has only the alternative of being right or wrong
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-Manfred Eigen
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A theory has only the alternative of being right or wrong
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-Manfred Eigen
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Modern agronomy, plant breeding, agrochemicals such as pesticides and fertilizers, and technological developments have sharply increased yields, while causing widespread ecological and environmental damage. Environmental issues include contributions to global warming, depletion of aquifers, deforestation, etc.
Fertilizers are used to supply crops with essential nutrients for growth and to help replenish the soil of key elements once a crop has extracted them during the growth process. Pesticides are chemicals which are used to control weeds and insects which pose a threat to crop production. If left unchecked, weeds can quickly outcompete the crop for essential light, water, and nutrients. Many kinds of insects feed on crops, damaging plants and limiting production. |
Water flow and solute transport modellingThe main challenge with respect to water flow model parameterization is how to develop a simple model with enough physical basis that represents the actual internal flow and transport pathways within a field. A validated flow model with good predictive ability of water flow dynamics can be used as the foundation for developing the solute transport model.
The main obstacle to this is the lack of sufficient field data on soil hydraulic properties. Determination of hydraulic properties through direct measurements is time consuming and costly, and often the lack of high-quality measured soil physical data is a source of uncertainty. The spatial variability of the soil properties within a field adds significant uncertainty in relation to the modeling results. Moreover, the spatial variability of the hydraulic properties is linked to the soil physical properties, which at field scale is related to the soil-forming factors where meteorological conditions, organisms, topography, and parent material are dominant factors. Therefore, prediction models that incorporate the spatial variability in soil physical properties within a field are considered important hydrogeological tools that cover the absence of knowledge regarding the parameterization of water flow models. |
Tile drainageTile drains are commonly used in agriculture areas as an important component in water management for removing the excess water when presence of shallow groundwater levels or seasonally perched water tables enhance the risk of anoxic conditions for the crops. In several studies, the tile-drainages have been considered a significant hydrogeological tool for inquiring into the spatial variability of soil properties in fieldscale since it integrates the hydraulic response of an entire field under different hydrological conditions. Moreover, much research has evinced the subsurface drains as an artificial pathway for water and solute transport, which decrease the residence times significantly in the soil porous medium. However, tile drainage networks decrease the likelihood of uncontrolled losses of pesticides and nitrate from fields using engineered systems (e.g., constructed wetlands) for treating the contaminated water
before recharging open surface or groundwater bodies. Drainage studies can be useful for assessing the impact of agricultural management practices and assist in developing agricultural management policy maps, which will assist in the establishment of a more targeted national regulation that will take into account the spatial variability of soil filtering capacity regarding the pesticides and nutrients. |
Preferential flowAn additional pathway for rapid transport of water movement and contaminant transport in structured soils is the preferential flow defined as the uneven and often enhanced movement of water and solutes through porous media formed by wormholes, plant roots, or planar fissures induced by shrinkage and swelling. The importance of preferential flow has been recognized long time ago, when Schumacher (1864) stated that “the permeability of a soil during infiltration is mainly controlled by big pores, in which the water is not held under the influence of capillary forces”. The dominant role of macropores is reflected by
the short residence times in the porous medium leading to the accelerated downward migration of contaminants. Providing a route to bypass the soil matrix through a short-circuiting, the natural potential of soils to adsorb and degrade the solvents to non-toxic compounds is dramatically reduced, since solute transport is taking place in a comparatively smaller part of the porous system. Moreover, the interrelationship between the orientation of the developed macropores and the installed subsurface drainage systems enhance the possibility of their direct connection. The interfering cones of depression in systematically tile-drained agricultural fields sustain and extend the depth into the soil profile of where oxic conditions support the development of macropores. The last years’ non-equilibrium preferential flow models have received increasing attention in modeling the water flow dynamics and the N and P forms fate across tile-drained agricultural fields . Different sophisticated models have been developed for describing the preferential flow and for investigating their important role in allowing the rapid breakthrough of surface-applied solutes through the vadose zone, for example, dual-porosity, dual-permeability, multi-porosity, and/or multi-permeability models . However, the difficulty in simulating the flow and transport processes in non-capillary dominated systems is the heterogeneity in matrix and macropore properties. |
“The trick to having good ideas is not to sit around in glorious isolation and try to think big thoughts. The trick is to get more parts on the table.”
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– Steven Johnson
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