Center pivot and other irrigation systems offer advantages over conventional dry-land farming such as timely and uniform application of water to meet plant needs and ease of application of fertilizers and herbicides. Fields located over aquafers, or adjacent to rivers or streams, or in proximity to impounded bodies of water are often utilized for irrigated farming in hopes of increasing productivity and profitability. Indeed, irrigation systems have been a boon for agricultural producers across the country, particularly in the western states, but their adoption should not be undertaken without consideration of their unintended consequences.
The native grasslands extending from New Mexico and Texas north through Colorado, Oklahoma, Kansas, Wyoming, Nebraska, and the Dakotas were once the victims of ignorance, greed, and desperation which resulted in the Dust Bowl. Now, a proliferation of pivot irrigation systems across the Great Plains has transformed the recovering prairie ecosystem into circles of green farmland. But this apparent panacea holds dangers that, if not addressed, may again prove injurious to agriculture and holistic biological system.
According to a report by the US Department of Agriculture, “Irrigation inevitably leads to the salinization of soils and waters” (Frequently Asked Questions About Salinity : USDA ARS) In arid and semi-arid areas, the accumulation of salts in the soil is a major problem associated with irrigation. Salt levels can rise to the point where they are harmful to crops and make ground water unsuitable for drinking. But there are other dangers and risks. Before succumbing to the lure of increases in quantity of vegetative production, management should take into account the following risks when farming under pivot and other irrigation systems, especially in the Great Plains:
1. Loss of soil minerals due to leaching
2. Lowering of soil pH (caused by dissolving of nitrates and other negative ions)
3. Changes in soil structure—away from spheroidal
4. Overall reduction in soil fertility
5. Oxidation of organic matter (due to tillage)
6. Reduction in soil water-holding capacity (due to loss of organic matter)
7. Production of less nutrient-dense crops
8. Production of lower quality crops—higher in carbohydrates and lower in protein
9. Changes in wildlife habitat
10. Changes in micro-climate
11. Increased potential for parasites and diseases in livestock, wildlife, and crops.
12. Depletion of aquafers
Installation of pivot irrigation systems typically subject the land to plowing and the loss of a year-round vegetative cover. They come at the cost of lost resilient, perennial vegetation that increases water infiltration, retains soil moisture, and reduces wind speed across the soil surface.
If we are not careful, we will once again see massive wind erosion of the soil, fruitless plains, and another dust bowl.