QUANTIFYING EFFECTS OF SOIL CONDITIONS ON PLANT GROWTH AND CROP PRODUCTION

Authors: Benjamin, Joseph; Nielsen, David; Vigil, Merle; Bowman, Rudolph

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2002
Publication Date: 9/1/2003
Citation: BENJAMIN, J.G., NIELSEN, D.C., VIGIL, M.F., BOWMAN, R.A. QUANTIFYING EFFECTS OF SOIL CONDITIONS ON PLANT GROWTH AND CROP PRODUCTION. GEODERMA. 2003. v. 116 p. 137-148.

Interpretive Summary: Soil management decisions often are aimed at improving or maintaining the soil in a productive condition. We used the Least Limiting Water Range (LLWR) as an alternative to bulk density as a soil quality indicator. The LLWR combines limitations to root growth caused by water holding capacity, soil strength and soil aeration into a single number that can be used to determine soil physical improvement or degradation. The LLWR appeared to b a good indicator of plant productivity when the full potential of available water can be realized, such as with wheat grown in a no-till system when the wheat followed a fallow period. The LLWR was a poorer indicator of plant productivity when conditions such as low total water availability limited the expression of the soil status on crop production. We developed the Water Stress Day (WSD) concept as an improved method to evaluate in- season soil effects on plants. The WSD was calculated by summing the differences of actual water contents in the field from the limits identified by the LLWR during the growing season. We concluded that the LLWR can be a useful measure of management effects on soil potential productivity. Knowledge of the LLWR for a soil can help the farm manager optimize growing conditions by helping schedule irrigation and for making tillage decisions. The WSD, calculated from the LLWR and in-season water dynamics, allows us to evaluate changes in the soil caused by differing soil management practices and identify critical periods of stress on the plant that can reduce production.

Technical Abstract: Soil management decisions often are aimed at improving or maintaining soil productivity. We used the Least Limiting Water Range (LLWR) to evaluate soil changes caused by soil management. The LLWR combines limitations to root growth caused by water holding capacity, soil strength and soil aeration into a single number that can be used to determine soil physical improvement or degradation. The LLWR was a good indicator of plant productivity when the full potential of available water was expressed, such as with wheat grown in a no-till system when the wheat followed a fallow period. The LLWR was a poorer indicator of plant productivity when conditions of low water availability limited crop production. Dryland corn yields were poorly correlated with LLWR indicating that, under dryland conditions, in-season factors relating to water infiltration may be more important to corn production than water storage. An improved method to evaluate in-season soil environmental dynamics was made by using Water Stress Day (WSD). The WSD was calculated by summing differences of actual water contents in the field from limits identified by the LLWR during the growing season. We improved the regression of corn yield to soil environment status from an r2 of 0.001 for LLWR to an r2 of 0.60 for WSD. We concluded that the LLWR can be a useful measure of management effects on soil potential productivity. Knowledge of the LLWR for a soil can help the farm manager optimize growing conditions by helping schedule irrigation and for making tillage decisions. The WSD, calculated from the LLWR and in- season water dynamics, allows us to evaluate changes in the soil caused by differing soil management practices and identify critical periods of stress on the plant that can reduce production.