WATER CONSERVATION AND EFFICIENT USE

Authors: Unger, Paul; PAYNE, WILLIAM - TAES; PETERSON, G. - COLORADO STATE UNIV.

Submitted to: American Society of Agronomy Monograph Series
Publication Type: Book / Chapter
Publication Acceptance Date: 1/15/2006
Publication Date: 10/15/2006
Citation: Unger, P.W., Payne, W.A., Peterson, G.A. 2006. Water conservation and efficient use. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series 23. Madison, WI:American Society of Agronomy. p. 39-85.

Interpretive Summary: Greater food production will be needed in the future under dryland conditions to meet the needs of the world's population that is always increasing. This is because water needed to expand irrigated areas is limited, being depleted, or being competed for by urban, industrial, and recreational users. For more production on dryland, precipitation water must be captured, saved, and efficiently used. In this chapter, we discuss principles and practices that should lead to greater production of dryland crops. To capture water, surface conditions must be such that water easily enters the soil. For this to occur, the soil must be protected by a cover of growing crops or crop residues from raindrops striking the surface. Tillage and other practices that keep the water on the surface or reduce its flow rate across the surface also help by providing more time for infiltration. To save the stored soil water, losses due to evaporation, use by weeds, and deep percolation must be reduced or prevented. Evaporation can be reduced by using mulches that reduce water vapor moving into the air, and, under some conditions, by tillage that interrupts water movement to the soil surface. Water use by weeds can be reduced by tillage (or hoeing), herbicides, or a combination of those methods. Deep percolation can be reduced by using crops that are growing when deep percolation is most likely to occur and by providing conditions for using water from deeper in the soil profile (growing deep-rooting crops, deep plowing to remove layers that restrict root growth, and using adequate fertilizers). For efficient use of water by dryland crops, the crop sequences used must match the conditions of the region to manage crop water use, ensure plant health, and manage production risks. A basic plan for choosing a crop for a particular system is that the time when the crop needs water the most must match the time when stored soil water and precipitation is most likely to be available. Crop production under dryland conditions will remain variable because of unreliable weather, mainly precipitation. Successful and sustainable production on dryland, however, is possible by using the principles and practices discussed in this and other chapters of this monograph to manage the crops.

Technical Abstract: Dryland agriculture will become increasingly important in our efforts to produce adequate food for an ever-increasing world population because water supplies for expanding irrigated areas are limited and/or being depleted. Also, there is increasing competition for water among agricultural, urban, industrial, and recreational users. To achieve greater production on dryland, precipitation water must be effectively captured and retained and efficiently used. In this chapter, we discuss principles and practices that should lead to improved production of dryland crops. The keys to effective water capture are surface conditions that allow water to readily enter a soil. To achieve this, the soil surface must be protected from raindrop impact energy, as by cover provided by growing crops and/or crop residues, or by tillage and other practices retain the water or retard its flow across the surface, thereby providing more time for infiltration. For maximum retention of stored soil water, losses due to evaporation, use by weeds, and deep percolation must be minimized or avoided. Evaporation can be reduced by mulching, which reduces water vapor transfer to the atmosphere, and, under some conditions, by tillage that interrupts water flow to the surface. Water use by weeds can be controlled by tillage (or hoeing), herbicides, or a combination of those methods. Deep percolation can be reduced by growing crops whose growing season coincides with the time when the potential for deep percolation is greatest and by encouraging water use from deeper in the profile (planting deep-rooting crops, deep plowing to remove root growth-restricting layers, and adequate fertilization). Efficient use of water by dryland crops requires appropriate crop sequences suited to the particular environment to manage crop water use, ensure plant health, and manage risk. A fundamental strategy of crop choice for a particular system is that its pattern of crop water demand match that of stored soil water and precipitation availability. Crop production under dryland conditions will remain variable because of the vagaries of the weather, mainly precipitation. Successful and sustainable production on dryland, however, is possible through careful management based on the principles and practices discussed in this and other chapters of this monograph.