Soil Thermal Regime Influence on Water Use and Yield under Variable Irrigation
- J.M Wraith and
- R.J. Hanks
Soil temperature has been shown to influence the early growth and development of many plants. It is not clear, however, how these findings are related to seasonal field soil water and crop growth dynamics. We conducted a study to investigate the seasonal influence of the field soil thermal regime on soil water depletion and growth of winter wheat and corn under variable irrigation levels, at Logan, UT, during 1987 and 1988. Soil surface mulches and buried heat cables were used to modify soil temperature, and a line-source sprinkler system provided a range of water application levels. Soil water depletion increased with soil temperature, and depth of maximum soil water depletion was 0.2 to 0.4 m deeper for warm than cool soil treatments during most of the growing season for both crops. This was true even where early-season temperature differences were minor or nonexistent. Earlier maturation of plants grown in the warmer soil caused reduced water uptake later in the season, resulting in similar cumulative soil water depletion for all temperature treatments. The depth of plant roots under low irrigation during 1988 increased with soil temperature, but this relationship was not consistent under the higher irrigation level. In 1987, soil temperature did not significantly affect final crop yields. Larger, and earlier, treatment differences in the soil thermal regime in 1988 caused significant plant growth responses to persist throughout the growing season. There were no interactive responses of plant growth and yield parameters to soil temperature and irrigation levels. Seasonal influences of the soil thermal regime on crop water use should be considered in applications where the seasonal status of soil water in the root zone is of fundamental importance.
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