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United States Department of Agriculture

Agricultural Research Service

Title: Modelling Corn Rooting Patterns and Their Effects on Water Uptake and Nitrate Leaching

Authors
item Benjamin, Joseph
item Ahuja, Lajpat
item Allmaras, Raymond

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 1995
Publication Date: N/A

Interpretive Summary: Ground water quality is affected by leaching of agricultural chemicals from the root zone. The public desire for improvements of ground water quality provides an incentive to explore the possible reduction of leaching by changing the rooting patterns of crops through genetic manipulation (plant breeding) or through soil management. Models have been used to predict crop management effects on chemical leaching in the root zone in agr. systems, but most modelling efforts have largely ignored the effect of the plant on such movement. Models of different rooting patterns and their effects on water and chemical movement may be useful tools for such explorations. Water and nitrogen absorption by corn is partly determined by the region in the soil containing roots and, as a result, rooting patterns could change water availability and leaching of nitrates. In order to investigate the effects of genetic as well as management-induced variations sof rooting patterns on water and nitrate movement, a two-dimensional model of corn root growth was developed and linked to a two-dimensional soil water, heat and solute transport model. Changing the root growth parameters allowed the model to be used to compare water uptake and NO3 leaching between a shallow, dense root system and a deep, sparse root system. Nitrate leaching was almost identical for both root systems. However, as compared with model simulations with no plant, plant uptake of water caused less downward movement of N. The model should be useful for examinations of water and chemical movement in the soil by including the effects of the plant in the system and allow at least a preliminary exam of soil management effects on corn rooting and water and nutrient availability.

Technical Abstract: Water and nitrogen absorption by corn (Zea mays L.) is partly determined by the region in the soil containing roots and, as a result, rooting patterns could change water availability and leaching of nitrates. In order to investigate the effects of genetic as well as management-induced variations of rooting patterns on water and nitrate movement, a two-dimensional model of corn root growth was developed and linked to a two-dimensional soil water, heat and solute transport model. The model was calibrated with root distribution and soil environment data from Lamberton, MN. Changing the root growth parameters allowed the model to be used to compare water uptake and NO3 leaching between a shallow, dense root system and a deep, sparse root system. The deep, sparse root system extracted a small amount of water from lower in the soil profile compared with the shallow root system, but most of the water for transpiration came from shallow depths directly below below the plant. Nitrate leaching was almos identical for both root systems. However, as compared with model simulations with no plant, plant uptake of water caused less downward movement of N. The size of the soil volume explored by the root system may be more important for determining water availability and possible plant water stress during dry periods than for decreasing fertilizer or pesticide leaching. The model should be useful for other examinations of water and chemical movement in the soil by including the effects of the plant in the system. The model also allows at least a preliminary examination of soil management effects on water and nutrient availability.

Last Modified: 7/24/2014