USDA Agricultural Research Service, Bushland, TX

The Great Plains is generally viewed as the nearly level, treeless, semiarid land west of the 98^th meridian and east of the Rocky Mountains. The western boundary is distinct. It borders the marked uplift of the Rocky Mountains. The eastern boundary is generally viewed as the line delineating the mixed-grass prairies of the Plains from the tall-grass prairies to the east.

The Great Plains was settled in the last 19^th to early 20^th century. Early settlers included farmers from the east looking for more and better land and immigrants from Europe. Although these settlers came from highly diverse backgrounds, they had a common goal: to establish farming operations that could provide for the well-being of their families. But for many, their dreams and aspirations were short-lived. Farms were too small and the environment was more harsh and arid than anticipated. The settlers brought with them their tools and knowledge that had been successful in humid regions, but they were unsuitable for the Great Plains. Early-day conservationists warned of the erosion that would take place in many parts of the Great Plains if the lands were cultivated. In spite of these warnings, land was broken from soil, and erosion problems – particularly wind erosion—became increasingly serious. The most rapid expansion in cultivated land took place in the decade of the 1915 – 25. Following World War I, high wheat prices, coupled with the development of power machinery, led to the rapid expansion in cultivated land and the large-scale production of wheat and other crops.

Two periods dominate the history of the Great Plains—The Dirty Thirties highlighted by the infamous Dust Bowl; and the Filthy Fifties (1950-56) which were the driest years ever recorded in the Southern Great Plains. The future of the Great Plains was in questions during these periods, and many forecasters thought the region had no future. The region, however, not only survived, but became one of the most productive areas in the world. The rapid expansion of the irrigation during the drought of the 1950’s played a major role in increasing and stabilizing crop production in the region.

The tremendous increase in energy costs during the 1970’s will also make this period of historical significance. Much of the irrigation development in the Great Plains occurred between 1945 and 1973 when a bushel of wheat or corn was of almost equal value to a barrel of oil (Figure 1). Since 1973, the number of bushels of grain required to purchase a barrel of oil has increased dramatically, and this has had a tremendous impact of Great Plains agriculture. The irrigated area in the Texan High Plains has declined from a peak of 6 million acres in 1974 to about 4 million acres as a result of increased energy costs coupled with continuing groundwater depletion, low farm profits, and government set-aside programs. The decline of irrigation in portions of the Great Plains and the low profitability of dryland systems, particularly in the more arid regions, has again raised questions about the future of the Great Plains. Frank and Deborah Popper, Rutgers University, recently predicted that over the next generation the region will inevitably become almost totally depopulated. The wisest thing the federal government could do, they argue, is to start buying back great chunks of the plains, replant the grass, reintroduce the bison – and turn out the lights. Although most of us vehemently disagree with that recommendation, we must agree that the Great Plains faces two critical issues. First, Great Plains agriculture is being challenged because of reduced profitability, degradation of the resource base, and detrimental impacts on the environment. Second, rural communities are eroding socially and functionally at an alarming rate. Unless we take immediate steps to address these key issues, we may sadly conclude that there is substantial truth in the analysis of Frank and Deborah Popper. The objective of my presentation is to briefly discuss the benefits that conservation tillage can have on the Great Plains.

Fig. 1

Conservation tillage was defined in 1983 by the Conservation Technology Information Center, West Lafayette, Indiana as "any tillage system in which at least 30% of the soil surface is covered by plant residue after planting to reduce soil erosion by water; or, where soil erosion by wind is the primary concern, at least 1,000 pounds per acre of flat small grain residue equivalent are on the surface during the critical erosion period." The USDA Soil Conservation Service adopted this definition in 1984. There are regions in the Great Plains, particularly during dry years, where there is not sufficient crop residue produced to fully comply with this definition even when no-till systems are practiced. Therefore, I will use the term conservation tillage in the broad sense of residue management rather than the literal definition. The important point to begin with, however, Is that it is absolutely essential, particularly under non-irrigated conditions, to manage residues on the surface to control erosion and reduce evaporation of soil water.

The key to sustaining the soil resource base is to maintain, or enhance, soil quality. Soil quality cannot be seen or measured directly from the soil quality. Soil quality cannot be seen or measured directly from the soil alone but which is inferred from soil characteristics and soil behavior under defined conditions. In essence, the quality of soils is synonymous with the health of humans. Likewise, just as there is no single characteristic that can be measured to quantify a person’s health, there is no single measurement that can quantify soil quality. However, there are certain characteristics, particularly when considered together, that are good indicators. Soil quality, just as human health, can be maintained or enhanced by good management practices; and seriously degraded, sometimes irreversibly, with poor practices.

Soils provide three critical functions. First, the most important, they provide a medium for plants with nutrients and water. Second, soils regulate the way water flows through watersheds. The rate at which precipitation infiltrates, moves through or is stored in the soil during a storm is critical for both crop production and the hydrologic cycle. Third, and increasing in importance, soils serve as environmental filters.

Soil quality is also important because it impacts directly and indirectly on air quality and water quality. While the enhancement of soil quality does not assure parallel improvements in the quality of air and water resources, particularly water quality, this is often the case. On the other hand, soil degradation is invariably accompanied by degraded qualities of air and water resources.

Although there is no single measurement for determining soil quality, an argument can be made that the organic matter content of the surface is an extremely good indicator. Organic matter contributes significantly to the productivity of a soil. It acts as a storehouse for nutrients, increases the cation exchange capacity, and reduces the effects of compaction. It builds soil structure and increases the infiltration of water. It serves as a buffer against rapid changes in pH and serves as an energy source for soil microorganisms. Therefore, a significant decrease in soil organic matter will generally also lead to a degradation in the quality of other commonly measured soil characteristics.

Soil degradation implies diminution of its productive capacity through intensive use leading to adverse changes in soil quality and other soil properties. Processes leading to soil degradation may be physical, chemical, or biological. The rate of soil degradation by different processes is greatly accentuated by using land for whatever it is not capable of and by unsuitable methods of soil and crop management. The factors driving degradative processes can be natural or impacted by man. Natural factors include climate, vegetation, parent material, terrain and hydrology. Important factors largely influenced by man include land use, cropping systems, and soil management practices. For most cropping systems, degradative processes and conservation practices occur simultaneously. The relationship of soil productivity and soil conservation is illustrated in Figure 2. As soil degradative processes proceed and intensify, there is a concomitant decrease in soil productivity. Conversely, soil conservation and restoration practices tend to enhance soil productivity. Therefore, the productivity level of an agricultural soil at any point in time is the result of the interaction of degradative processes and conservation/restoration practices shown in Figure 1. In natural ecosystems, productivity and sustainability are achieved through the efficient but delicate balance between all necessary inputs and outputs. Failure of cropping systems to maintain this balance will ultimately lead to a decline in soil productivity. Perhaps the most dominant soil degradative processes in the Great Plains are soil erosion and organic matter decline.

Fig. 2

Fig. 3

Climate is often the most critical factor determining the sustainability of soil resources. A generalized view of the effect of varying temperature and moisture regimes on the difficulty of achieving sustainability of agricultural systems is presented in Figure 3. As temperature increases and amounts of precipitation decrease, the development of sustainable systems becomes more difficult. The reasons for these effects are readily apparent when processes and practices presented in Figure 2 are analyzed. As temperatures increase, organic matter decomposition increases. The potential for erosion, particularly wind erosion, also generally increases in warmer areas. These same degradative processes are accelerated in areas of lower precipitation because there is a lower inherent organic matter level and less natural vegetation to prevent erosion. Not only are the soil degradative processes greater under hot and dry climatic regimes, the benefits that can be derived from soil conservation practices in these regimes than those in cooler and wetter areas. For example, the most important soil conservation practices to alleviate organic matter loss and control soil erosion usually involve crop residues, and the availability of residues decreases sharply in hot and dry areas. The data presented in Table 1 show that an inch of water, above a threshold amount, in the Northern Great Plains produces more than twice as much wheat grain as an equal amount of water can produce in the Southern Great Plains. Likewise, similar differences occur in the amounts of residues produced. Water is not as efficient in the Southern Great Plains because of the significantly higher vapor pressure deficits as compared to the cooler regions of the Central and Northern Great Plains.

Table 1. Threshold^a and grain yield per inch of water for winter wheat at several U.S.A. locations.

Gains in fallow efficiencies resulting from reducing tillage in the Southern Great Plains have been less, but still significant, than those presented above for the Central Great Plains. This is largely due to having less crop residues because of lower yields associated with the higher water requirements in hotter and dryer climate. Soil water storage during the approximate 4-month fallow period of continuous wheat at Bushland, Texas, was 3.6 inches when oneway disk tillage was practiced, compared to 4.1 inches with stubble mulch tillage. For wheat-fallow (approximate 14 month fallow period), the water storage values were 4.0 inches and 6.1 inches for the oneway disk and stubble mulch treatments, respectively (Johnson et al., 1974). More recent studies by P.W. Unger (unpublished) have compared stubble mulch tillage with no-till. Unger used a wheat-sorghum-fallow rotation (two crops in 3 years with approximate 11-month fallow periods between crops) and compared a dryland system with one where the wheat crop was irrigated and succeeding grain sorghum crop was dryland. The irrigated wheat produced a large amount of crop residue that served as an effective mulch for increasing the fallow efficiency during the 11-month fallow period following wheat harvest and this increased stored water and enhanced grain sorghum yields significantly. Unger (Table 3) showed that soil water storage during the fallow period was increased from 174mm for sweep tillage (stubble mulch) to 212 mm for no-till. However, Unger did not find any increased soil water storage with no-till in the dryland system. Unger concluded that the amount of residue produced by dryland wheat in the semiarid portion of the Southern Great Plains was generally insufficient to have a pronounced effect on soil water storage.

Table 3. Average available soil water contents at sorghum planting in winter wheat-grain sorghum rotations (P. W. Unger, Bushland, TX unpublished).

Nowak (1991) states that answering the question of why farmers adopt production technologies is elementary and apparent; now production technologies are adopted when these techniques are perceived as being in the farmer’s best interest. Almost everyone would agree with this basic premise. Disagreements emerge, however, when asking the more interesting and challenging question; why don’t farmers adopt conservation tillage? Any effort to increase the rate of adoption of residue management systems must be based on understanding why farmers reject new production techniques. Now asserts that farmers do not adopt technologies for two basic reasons; they are unable or unwilling. These reasons are not mutually exclusive. Farmers can be able yet unwilling, willing but unable, and of course both unwilling and unable. Being unable to adopt to a new technique implies presence of an obstacle or constraint creating a situation where the decision not to adopt is rational and correct. Nowak (1991) listed nine reasons that farmers are unable to adopt conservation tillage, and seven reasons for which they are unwilling to adopt the technology.

1. Information is lacking or scarce.
2. Costs of obtaining information is too high.
3. Complexity of the system is too great.
4. System is too expensive.
5. Labor requirements are considered excessive.
6. Planning horizon is too short
7. Availability and accessibility of supporting resources is limited.
8. Inadequate managerial skills
9. Little or no control over the adoption decision

1. Information conflicts or inconsistency.
2. Poor applicability and relevance of information.
3. Conflicts between current production goals and the new technology.
4. Lack of knowledge on part of the farmer or promoter of the technology.
5. Practice is inappropriate for the physical setting.
6. Practice increases risk of negative outcome
7. Belief in traditional practices.

Nowak (1991) also presented some remedial strategies that may be helpful for increasing the rate of adoption. Finally, he made three concluding observations. First, increasing the adoption of new technology is dependent on first addressing reasons why farmers are unable to adopt. Once these impediments are removed, then it is a question of persuading the farmer from being unwilling to adopt. Second, many of the factors causing farmers to be unable to adopt are beyond their control. Blaming the farmer for not adopting a residue management system is not only erroneous in many cases, it is also hypocritical. Third, broad-scale use of any one or even several remedial strategies is doomed to failure. A "shotgun" approach of technical, financial, and educational assistance is not the answer. Instead, considerable more effort needs to be spent trying to understand the reasons why farmers are unable or unwilling to adopt. Based on that understanding, specific types of assistance for farmers should be tailored in a format compatible with their capabilities.

The Great Plains states account for 41% of the 430 million acres of cropland in the U.S. , and 43% of the 51 million acres of irrigated land (U.S.D.A., 1988). The amount of cropland used depends on several factors, and export demand is among the most dominant. The Great Plains is greatly affected by export demand. Therefore, the future of the Great Plains will be affected perhaps more than any other farming region in the U.S. by world events and grain exports in particular. The Resource Conservation Act of 1977 (RCA) requires the U.S.D.A. to continually appraise the use, conditions, and use trends of nonfederal land. The second RCA appraisal (U.S.D.A. , 1989) projected trends that are of special interest to the Great Plains. The study considered long-term trends of agricultural commodity demand, resources available, and changes in technology and used a computer model to analyze different demand scenarios. The analysis suggests that assuming intermediate raises of increase in export demand and in agricultural productivity, soil and water resources would be more than adequate to meet projected needs for food and fiber over the next 50 years. In contrast, meeting the highest projected levels or demand at the lowest projected rate of increase in productivity, a high stress situation, would require use of all available cropland by 2030. The projected cropland acreage needed to meet domestic, livestock, and export demand for the intermediate scenario (considered in the study as the most likely) and the high stress scenario are compared to the1982 cropland use in Figure 4. The most likely scenario suggests that only 218 million acres of cropland would be needed, which is less than 60% of the amount used in 1982. More important to the Great Plains, the analysis projected that a disproportionately large portion of the decrease would come from the Great Plains states (Figure 5). More than 50% reductions in cropland usage in some of the Great Plains states are suggested, while there would be practically no significant change in other major regions such as the Corn Belt. The RCA study emphasizes that these are projections of what would happen if certain trends continued, and should not be considered as predictions. However, it points out the dependence of Great Plains agriculture on exports.

Fig. 4

Fig. 5

The Great Plains is an important farming region of the U.S. for both dryland and irrigated cropping systems. Conservation tillage, starting with stubble mulching in the late 1930s, has become one of the most important management practices. Tillage systems that leave crop residues on the soil surface are essential to control wind and water erosion in most areas of the Great Plains. Conservation tillage also increases soil water storage during fallow periods, but these increases have been greater in the central and northern areas than in the southern areas. This increased soil water storage has resulted in greater crop yields for all regions, but the larger water storage increases in the central and northern areas allowed for the more efficient use of other improved technologies, primarily fertilizers and improved cultivars.

The extent to which cropland in the Great Plains is used in the future will depend largely on export markets for grain crops. Grain exports from the U.S. have historically varied by large amounts and there is no reason to believe that the future will be different. Therefore, the real challenge for Great Plains agriculture is to develop flexible production systems, including livestock, that allow cropland to go in and out of grain production. The Conservation Reserve Program provision of the 1985 Food Security Act has removed almost 20 million acres from crop production in the Great Plains I states. Future use of this land is a question of concern.

References

Allen, R.R. , and C.R. Fenster. 1986. Stubble-mulch equipment for soil and water conservation in the Great Plains. Journal Soil and Water Conservation 41:11-16.

Greb, B.W. 1979. Technology and wheat yields in the Central Great Plains: Commercial advances. Journal Soil and Water Conservation 34:269-273.

Johnson, W. C. , C. E. Van Doren, and E. Burnett 1974. Summer fallow in the Southern Great Plains. pp. 86-109. In. Summer fallow in the western United States. Conservation Research Report No. 17. U.S.D.A. Agricultural Research Service, Washington, D.C.

Montana Cooperative Extension Service/Montana Agricultural Experiment: Station1985. The Montana Small Grain Guide. Montana State University, Bozeman, Montana.

Nowak, Peter. 1991. Why farmers adopt product technologies. In Proceedings of Crop Residue Management for Conservation Conference, August 9, 1991.Lexington, Kentucky. Soil and Water Conservation Society, Ankeny, Iowa.

Stewart, B.A. , R. Lal, and S.A. El-Swaify. 1991. Sustaining the resource base of an expanding world agriculture. p. 125-144. In. R. Lal and F.J. Pierce (eds. ) Soil Management for Sustainability. Soil and Water Conservation Society, Ankeny, Iowa.

U.S.D.A. 1989. The Second RCA Appraisal. 280 pp. United States Department of Agriculture, Washington, D.C.