S1018: Irrigation Management for Humid and Sub-Humid Areas
Statement of Issues and JustificationCompetition for limited water resources is one of the most critical issues being faced by irrigated agriculture in the United States. As competition increases, agricultural irrigation must be considered a beneficial and wise use of water for it to remain a priority to the general public. In the 1978 to 1997 period, irrigated acreage in the western states declined by 0.6%, while in the southeastern states, irrigated acreage increased by 70% or 3.8 million acres (1.5 million ha) (Fig. 1). Irrigated land areas in the southeastern US are increasing, with almost 18.5 million acres reported by the USDA in the year 2000 (Table 1). Increasingly competitive agricultural markets require supplemental irrigation to avoid crop failures in dryer years and to assure high quality of agricultural products. With supplemental irrigation practices becoming common practice in agriculture and landscape management in the southeastern US, there is a strong need for coordination of research and extension programs in water management. Significant resources have been expended to develop irrigation research parks in many states in the humid and sub-humid region. Research and extension efforts need to be efficient, collaborative, and beneficial to the larger clientele group within the area.
Irrigation also has a direct impact on the quality of water resources. Soil water content is maintained at a higher level under irrigated conditions. As rainfall events occur, there is greater potential for leaching and runoff of soil, nutrients, and pesticides because of less available storage for rainfall water. More efficient alternatives are required to meet desired water quality objectives. Efficient water use in irrigation to meet quantity and quality constraints in the sub-humid and humid regions of the United States is a critical need.
Please see Figure 1 in Attachment 1 for the map of the United States at the bottom of the proposal.
The recent drought period between 1998 and 2002 exacerbated the growing pressure on existing water supplies due to irrigation, population growth, and human activity. According to NOAA, the southeast US has experienced more frequent droughts than usual. At its peak in the year 2000, the drought affected about 36% of the contiguous U.S. The areas most severely affected included the deep south, the southern and central Great Plains, and much of the western United States (Fig. 2). Weather variability is expected to continue into the future. Addressing short-term and long-term droughts, along with excess rainfall conditions will be a continuing problem in the humid and sub-humid regions.
Please see Figure 2 in Attachment 2 for the Palmer Drought Index at the bottom of proposal.
Table 1 presents the most current census data available for the southeastern states presented as total acreage irrigated in each state, and the types of irrigation systems used for supplemental irrigation in these states. The total irrigated acreage in the Southeast was estimated to be 18.5 million acres in 2000. Notably, the use of microirrigation, potentially the most efficient irrigation method, has increased 15 fold in the last 20 years, reaching almost one million acres in 2000. Unfortunately, microirrigation still represents only about 5% of the total irrigated land area. At the same time there is a decrease in number of acres irrigated by gravity (surface flood and furrow irrigation approaches). Gravity irrigation methods are still used on about 50% of the irrigated land area. All land areas are not conducive to conversion from gravity to sprinkler irrigation methods (such as center pivots) due to the soils and inability to support heavy traveling irrigation systems when the soils are wet. Microirrigation will continue to be more applicable to high value crops. Row crop irrigation will require more economical irrigation options due to the rate of return on irrigation investment.
Since 1978, irrigation expansion in the southeastern states has occurred entirely without large federal or state projects, and has been the responsibility of individual farm operators who obtain water from wells drilled on their property or water that they divert from adjacent streams or drainage flows. In contrast to the large federally funded projects in the West, which were supported historically by a strong university, USDA-ARS, Corp of Engineers, and USDA-NRCS research and extension effort, southeastern irrigation expansion in the last 25 years has largely occurred without strong research and extension efforts in the affected states. This view is supported by the fact that roughly three quarters of the ARS irrigation research scientists are located in the western states. Currently, very few ARS water management research scientists are located in the Lower Mississippi River Valley (LMRV) and several of those have been dedicated almost entirely to drainage research. Some research efforts were directed toward subsurface irrigation (adjusting the shallow water table below crops). Sub-irrigation practices have been adopted fairly widely in Florida and North Carolina, with some use in South Carolina (Fouss, 2002). There has been limited adoption in other states.
Please see Table 1 in Attachment 3 at the bottom of proposal.
In the southeastern states, the recent formation of irrigation districts is occurring in areas already heavily irrigated by individual farm operators. These efforts to improve management of limited water resources represent an attempt to address ground water decline problems by a combination of three approaches: (i) water conservation and management using on-farm storage reservoirs, tail-water recovery systems, replacement of open ditches with underground pipelines, and improvements in irrigation methods; (ii) replacement of well water sources with surface water sources, and (iii) future reductions in allocated water for irrigation purposes.
In Missouri, Henggeler (2000) estimated that $95 million of market value was lost due to yields of irrigated crops being below the most economical and attainable yields. He recommended support for research on irrigation scheduling because correct scheduling had the most potential for improving yields. On corn, cotton and full-season soybean, irrigation amounts and number of applications are approximately one half of what they should be for conservative yield goals of 190 bu/ac (11,900 kg/ha) of corn, 1000 lbs/ac (1120 kg/ha) of cotton, and 60 bu/ac (3800 kg/ha) of soybean in Missouri (Henggeler, 2000).
In Mississippi, irrigated acreage grew from 161,000 acres (65,000 ha) in 1974 to 1,076,000 acres (436,000 ha) in 1997, most of it in western Mississippi, including the Yazoo and Mississippi river drainages (NASS, 1998a). In 1997, soybeans occupied 41% of irrigated land, followed by cotton on 28%, rice on 22%, and corn on 8%. The major crops in Mississippi are cotton, corn, and soybean in order of decreasing economic importance. About 24% of corn acreage, 29% of cotton acreage, 24% of soybean acreage, and all rice acreage are irrigated. The market value of all crops was $1.29 billion in 1997. Most irrigation water in Mississippi is pumped from the Alluvial Aquifer, which underlies about 7,000 square miles (18,000 km2) in 19 counties of western Mississippi. Water pumped from the aquifer has increased from 745 million gallons (2.8 million m3) per day in 1975 to approximately 2 billion gallons (7.6 million m3) per day in 1994. These pumping rates are expected to continue to rise based on increases in land acres under rice production, and improved risk management for row crop production (Arthur and Strom, 1996). There is concern that Mississippi will experience the aquifer declines already evident in Arkansas; and the Alluvial Aquifer is being closely monitored cooperatively by the USGS and the Yazoo Mississippi Delta Joint Water Management District (Pennington, 2002).
In Louisiana, irrigated acreage has not changed as rapidly and consistently as in Arkansas and Mississippi, increasing from 702,000 acres (284,000 ha) in 1974 to just 943,000 acres (382,000 ha) in 1997 (NASS, 1998a). Rice is planted on 61% of irrigated land, cotton on 17%, corn on 9.7%, and soybean on 8.6% (NASS, 1998d). Sugar cane is almost entirely non-irrigated; but surface drainage is practiced on most sugar cane fields. Drainage here involves a combination of precision graded fields, shallow drainage ditches, and "quarter drains" formed annually to divert runoff across rows to the closest ditch. Sugar cane acreage was 396,000 acres (160,000 ha) in 1997, up from 356,000 acres (148,000 ha) in 1992. The market value of all crops in Louisiana was $1.41 billion in 1997. While all rice is irrigated, just 22% of corn, 25% of cotton, and 6.4% of soybean are irrigated (NASS, 1998d). This leaves the potential for more irrigation, particularly in the Mississippi River Valley of northern Louisiana (Fouss, 2002).
Irrigated lands in the Lower Mississippi River Valley (LMRV) surpassed 6.5 million acres (2.6 million ha) in 1997 and are increasing at a rate of 189,000 acres (77,000 ha) per year. Arkansas is experiencing the most rapid increase in irrigation and is now the fourth ranking irrigated state. Annual farm gate receipts in the four most heavily irrigated LMRV states, Arkansas, Missouri, Mississippi, and Louisiana, exceed $8 billion. Despite annual rainfall greater than 40 inches (100 cm), periodic summertime drought makes irrigation necessary to avoid crop failure and yield reductions. Little of the irrigated land is within organized irrigation districts. The increase in ground water pumping has resulted in aquifer depletion, particularly in eastern Arkansas, resulting in a need for surface water diversion to replace well pumping. Currently, ten irrigation projects are in the planning or construction phase in Arkansas. However, lack of scientific data about water quality, management efficiency, and environmental impacts in humid region irrigation schemes is a major impediment to project design and public acceptance, not only in Arkansas but in other Delta states (Evett et al., 2003).
The overall goals of this multi-state project will be to coordinate research and extension programs that are associated with irrigation management in the sub-humid and humid regions of the United States. The emphasis of the project will be toward practices, systems, and approaches that will provide improved use and reduced impacts of water associated with irrigation on a local and multi-state scale (based on the resource). The larger scale emphasis implies a need for addressing problems and implementing solutions comprehensively so that irrigators can continue to improve their responsibility as partners in the effective use of limited water resources. These issues will logically involve agricultural, urban, and agricultural/urban interface areas. The direct impact of irrigation on the quality of water resources is important to this project. More efficient irrigation alternatives will be required to meet desired water quality objectives. An over-riding emphasis of this project is to encourage approaches toward maximizing the net benefits of irrigation (English et al., 2002) and making sure these approaches are available, understandable, and feasible for current and future irrigators.
A. The need as indicated by stakeholders. The individual commodity commissions throughout the southern region have listed irrigation as one of the top 10 priorities for funding research for at least the last five years. The need to improve water use efficiency while effectively using water for the economical benefit of crop production is essential. Numerous areas in Florida, Georgia, and other locations will not be able to meet projected water demands based on current usage growth within the next decade. Much of the water used is for residential and agricultural irrigation. Water management districts and local municipalities have indicated the need for water conservation to extend the use of current water supplies. Proper management of existing irrigation systems and proper design of future systems is critical to ensure effective use of water supplies. In Georgia, increasing demand for water will affect the priority and partitioning of water resources for irrigation use (whether agricultural or landscape) when compared to consumptive and industrial demands.
B. The importance and extent of the problem. The extensive drought throughout the humid and sub-humid areas across the United States between 1998 and 2002 increased the emphasis toward reducing the risks associated with water availability to crops and plants. This increased need for better water management is also associated with economic and environmental incentives based on low commodity prices and additional regulations associated with water resources (such as TMDL designations). Coupled with the recent drought is the growing pressure on existing water supplies by growing population and human activity.
C. The technical feasibility of the research. Each participant in this research program has experience with irrigation research and/or is associated with a funded (or anticipated) irrigation research park or facility. Project plans and procedures indicated below outline the scientific basis for high quality research that is publishable and useable by clientele.
The organizational support for irrigation research is quite extensive throughout the humid and sub-humid region indicating this type research is a priority. The potential to meet irrigation research needs while minimizing duplication across similar crop, climatic, and physiographic locations encourages more efficient utilization of funding for irrigation research. For example, irrigation research on scheduling of peanut irrigation occurs in Georgia (more than one location), Florida, Alabama, and Texas. Researchers are investigating approaches ranging from computer-based irrigation scheduling to sensor feed-back controls to on-farm irrigation scheduling devices. Each of these approaches has merit to a different population of farmers and other end users involved in irrigation. However, collaboration across locations is expected to yield more comprehensive results.
D. The advantages of doing the work as a multi-state effort. There are substantial differences in available water resources, water management needs and strategies across state lines. By combining research across states, innovations that are utilized in one region could be applied successfully in another region. In addition, a multi-state effort maximizes the benefits gained from dwindling research dollars from individual institutions and organizations.
Biologically, crop water-use is highly dependent on both plant genetics and environment. By addressing these issues as they relate to plant water requirements, water-use efficiency, and irrigation system application efficiency on a regional and multi-state scale, we can provide improved recommendations for reducing irrigation water use while maintaining the desired plant environment. Collaborative efforts across organizations and states are already being discussed for the following specific project areas:
Potential for enhancing precision water application technologies
Nursery production alternatives with the UFL boxes Soil management and cropping system effects
Level basin irrigation
Implementation of irrigation scheduling technologies on the web
Spectral assessment of crop water status
Empirical and field studies on irrigation deficits
The potential to achieve these project objectives with direct economic potential are greatly enhanced by a multi-state effort.
E. Benefits or impacts of the research or information exchange, including impact on science. Using a multi-state approach to meet these objectives will allow plot-, field- and national-scale methodologies to be implemented with a reduced potential for overlap between locations. In addition, technologies can be explored for compatibility across different physiographic, soil, and climatic conditions to ensure application potential of resulting technologies. For example, cotton is irrigated in several locations throughout the humid region. Irrigation scheduling, profitability characteristics as associated with irrigation water management, and cultivar responses to irrigation management alternatives would benefit from a comprehensive regional effort.
Landscape and turf irrigation are also practiced across the entire humid and sub-humid region. The potential to save water via conservation, improved sensor technology and better scheduling could reduce the potential for severe water restrictions to be implemented. Within the past five years, complete outside watering bans have been utilized in many communities in humid and sub-humid areas to help conserve water resources. Individual users and the nursery industry (one of the fastest growing agricultural enterprises in the United States) would greatly benefit from approaches that would not require watering bans.
Much of what we know about irrigation was developed in areas where rainfall is minimal. The applicability of such results to the humid and sub-humid region is still a question, especially for irrigation scheduling practices. Irrigation science will require more critical assessment of economic potential and risk assessment because rainfall can help in many years. The costs of installation and operation of irrigation systems over the long term must match up with the benefits.
F. Identify the stakeholders, customers, and or consumers of the project results. Irrigated farms throughout the humid and sub-humid region, homeowners and businesses with irrigation, state and national agencies that are responsible for reducing water consumption and improving the efficiency of water management, and all those who benefit from another water user improving their efficiency of water use will benefit from this research and technology transfer effort. One additional example (associated with the National Peanut Research Laboratory) is the creation of an industry and stakeholder map identifying all the key points in the peanut industry. Irrigation water applications are components in a comprehensive analysis of costs and returns on those investments. In Florida, the stakeholder group includes 17 million water users and consumers. An in-ground irrigation system is standard in new home construction in the state and over 12% of all new home construction in the US occurs in Florida.
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