Most of the Great Plains have always been considered a semi-arid area of the U.S. This Region is characterized by hot, relatively short summers (with a rainfall pattern), and usually cold, dry winters. Annual precipitation increases by almost 70 percent between the Western (East of the Rockies) and Eastern ends of the Region. Potential moisture losses by evapotranspiration also increase by almost 400 percent between the Northern (Canadian border) and the Southern extremes. In addition to these moisture gradients, agricultural production is challenged by high climate variability interspersed with periods of severe precipitation shortages. Susceptibility to drought is not only determined by the yearly precipitation but also by the moisture storage capacity of the different types of soil. The map shows that west of the Missouri river the moisture storage capacity is low compared to the east, which is similar to other highly crop-producing regions of the Midwest. Even during years of normal rainfall there can be short-term dry periods that can affect crops.
Long-Term Drought Projections
In a February 2015 report NASA suggested severe droughts in the Central Plains during the last half of this century could be more extreme and longer than those verified in the last 1,000 years. The agency further stated the dry spell would probably last for as long as three decades. The map below shows that depending on the location in the state the best scenario has been a drought every 5 years for Northeast South Dakota, followed by almost one every 4 for East Central and Southeast, one every 3 for South Central and Southwest, and one every 3 to 2 for the North Central and Northwestern part of the state. If what NASA predicts for the future should become a reality, additional management strategies will have to be utilized in the Great Plains. Agriculture practices will have to adapt to production systems already common in areas where precipitation or even water supply is frequently limiting.
Dryland Farming Techniques
Dryland crop farming needs specialized management techniques that allow for the efficient use of rainfall and minimizes crop losses when precipitations are scarce. High average rainfall during the year cannot be used as a reliable predictor of a great crop-year. In fact, torrential rainfall can lead to ponding, nutrient leaching, plant losses, and it’s also a powerful agent of erosion. It is the timing of rainfall that is critical, and not the total inches during the year. In corn for example the most susceptible periods are the early reproductive stages, such as tasseling and silking. Soybeans, on the other hand, are most sensitive to moisture stress during the mid to late reproductive stages. Even short periods of drought stress during these critical developmental stages can result in yield losses.
Adoption of specific dryland farming practices vary depending on local physical and social variables. It also poses risks as it requires farmers to rely on rainfall, trap it in the soil, and sustain it for prolonged dry periods. Soil and water-conservation strategies such as increasing plant cover are also used. The use of narrow crop rows, intercropping and inter-planting in dryland farming increases the density of the plant canopy and reduces the impact of the raindrops on the surface of the soil and thus runoff and erosion. No-till management is a practice of choice in drier areas of the country. Results of the 2015 South Dakota Cropping Systems Inventory of December 2015 shows an upward trend in no-till farming systems in South Dakota acres since the 2013 inventory, and up significantly from 2004. The 2015 inventory found that 46 percent of South Dakota cropland is under no-till (6.47 million acres).
New technologies and farming practices have allowed this region to dramatically increase its agricultural output over the last century. This was mostly done by adapting the crops genetics to the soils and climate of the region. In fact, some livestock producers in Eastern South Dakota are being proactive and are experimenting with sorghum for silage as an alternative to corn. The development of more hybrids that tolerate drier conditions needs to continue. Techniques such as precision agriculture are proposed to sustainably increase the utilization of this land base. Precision agriculture will ensure the optimum amounts of fertilizers, pesticides, and water are utilized to optimize crop production.