How does drainage relate to water conservation?
The efficiency of water use by agricultural crops is often quantified by a value termed ‘water use efficiency” (WUE). Crop WUE can be calculated a variety of different ways, the most common one being the ratio of harvestable crop per unit of water use. For example: the water use efficiency of wheat production might be something like 7 bushels/acre/acre-inch of water use. Thus, a wheat crop which transpires the equivalent of 7 acre inches of water would yield 49 bushels of wheat/acre (7 bushels/acre/acre-inch x 7 acre inches=49 bushels/acre). In a poorly drained soil, some of the measured water use may actually be ‘water loss’ due to evaporation. Additionally, the ability of a crop to physiologically perform is impaired by saturated soil conditions and poor aeration status in the root zone. Under those conditions, WUE is likely to be less than under ideal conditions, i.e., good drainage. Thus, either more water is required to produce the crop or less of the available and crop-used water
