Relationship of the Soil Water Content and Microclimate to the Plant Growth Water Use Relationship of Several Plants

Studies involving field plots, lysimeters, and garbage can lysimeters showed that an intermediate soil water level produced the most growth for a given amount of water use by oats, corn, and barley. For crested wheatgrass the lowest water level produced the most growth per water used. Field plots which were covered with sheet metal between the rows produced more plant growth per water used than the uncovered plots for the crops used in this study. One year\u27s data were obtained on the effect of positioning the garbage can lysimeters. One half of the cans were placed on the soil surface and the other half were sunken into the soil, level with the soil surface. The data indicate no difference in water use efficiency between the two positions of the can. A new method was used to obtain garbage can size soil cores that were relatively undisturbed. The data for the field plots indicates that the field plots were more efficient in water use than the lysimeters; however, there are indications that all the water used by the field plots were not measured. A review of the literature on water use efficiency indicated the field values from this study were probably too high. It was possible that the roots were extracting water below the measuring depth or that the water was moving up through the profile in the field plots and the lysimeters (or cans) were the same, showed that the field plots could have received up to about 21 centimeters (cm) of water not accounted for in the soil depletion measurement