1a. Objectives (from AD-416)
(1) Develop methods and techniques for design, operation, and management of irrigation systems in the Mid-South region. (2) Develop and evaluate the benefits and limitations of site-specific management technologies for irrigated agriculture in the Mid-South region. (3) Determine interactions between irrigation and agronomic practices, and identify cultivars/practices to overcome problems encountered in irrigated cotton and soybean production for the Mid-South region. (4) Determine the impacts of irrigation and irrigated crop production on water quality in the Mid-South region.
1b. Approach (from AD-416)
To optimize irrigated crop production and protect soil and water resources in the Mid-South, it is necessary to consider natural soil variability within fields, the range of crops and production systems, and the types of irrigation systems employed. Our interdisciplinary team will address limitations to the overall goal of improving performance, profitability, and sustainability of Mid-South agriculture. We will investigate ways to improve irrigation scheduling and mechanized-irrigation-system management in spatially-variable soils. We will explore use of commercial sensors to provide information regarding crop water status and flood-water depth. Building on our previous research, we will investigate flood tolerance among cotton and soybean cultivars and plant introductions to reduce the risks associated with irrigating in humid climates; and investigate the water quality impacts of irrigated agriculture. We will investigate advantages and limitations to site-specific irrigation. Building on our long-term experience with irrigation scheduling, we will assess the options available for Mid-South irrigators. Site-specific irrigation and rice production system evaluations will include on-farm research with active participation by crop producers and crop advisors. Products of this research will include a sensor system for monitoring rice fields, water-conserving production systems for rice production, and improved flood tolerance for surface-irrigated Mid-South crops.
3. Progress Report
Efforts concentrated on continuing studies described in Project Plan that include objectives from both ARS and University of Missouri scientists. Under ARS leadership: 1. In cooperation with NRCS, a rice producer in the Conservation Security Program, the University of Arkansas, and a private company, wireless sensors were scheduled to be installed in two rice fields to alert the producer when water levels in paddies were low and when paddies were full. However, the vendor experienced equipment problems and the participants agreed to delay implementation until the 2010 growing season. In conjunction with an NRCS CIG project, pumping plants and irrigation reservoirs on Arkansas rice farms were monitored, with additional systems being added as possible. 2. The center pivot irrigation system equipped for variable rate application and used in the study was sold by the cooperating landowner, so the study ended. The monitoring equipment will be used in other studies to investigate energy use for irrigation. 3. Determined potential monitoring sites for automated runoff sampling; investigated preferred site and determined access was unsuitable; continuing to search for acceptable site for long-term water quality monitoring in the Little River Ditches watershed. Through the Specific Cooperative Agreement with the University of Missouri Delta Center (see also 3622-13610-002-01S, Improving Irrigated Crop Production in Southeast Missouri): 1. Used 152-m pivot to incorporate variability into irrigation management. Soil maps, soil textural field samples, and aerial photos were used to divide the field into specific irrigation treatments for corn. Adapted study to allow spatially referenced yield data. 2. Studies addressed twin-row production of corn, cotton, and soybean on sandy and silty soils. Results from 2008 showed that twin row production almost always produced higher yield then single row production. 3. Compared irrigation recommendations based on automated sensor systems to irrigation scheduling software. Results in 2008 indicated similar yields between the methods. 4. Arranged to install dataloggers and sensors to measure operating characteristics on electric, open-discharge wells. 5. Completed final season of small-plot studies employing a wide range of cotton seeding rates on sandy and silt loam soils; large-plot tests planned as a follow-up will be delayed until vacant cooperator position is filled. 6. Screened commercial cotton (56) and soybean (196) varieties and soybean plant introductions (642) and observed differences in tolerance to waterlogging. 7. Developed experimental crop coefficient function, adapted a computerized irrigation scheduling program to accommodate rice, and installed soil moisture sensors for monitoring soil moisture in a combination of small plot and large block rice studies under center pivot irrigation. Yields from large blocks will be spatially referenced.
1. Quantified effect of waterlogging on soybean growth. Soybean cultivars with a range of tolerances to excessive soil water were evaluated for the effects of flood duration and timing on clay and silt loam soils. Nitrogen concentrations in all cultivars were significantly reduced by extended flooding on clay, but no significant reduction was found on loam. Most cultivars were able to withstand short-duration flooding without crop injury; however, all cultivars were injured when extended soil waterlogging occurred due to excess rainfall after flooding treatments. Cultivars suffered less yield loss from flooding during vegetative growth than from flooding during reproductive growth. Results are important because surface irrigating soybean prior to a large rainfall can reduce crop yield, and a large rainfall can occur at any time during the growing season. Better understanding the intensity of yield loss due to waterlogging will result in best management practices to reduce the negative impact. Refereed Publication serving as basis for accomplishment (SCA publication with no ARS co-author; not in ARIS): Rhine, M. D., Stevens, G., Shannon, G., Wrather, A., Sleper, D. Yield and nutritional responses to waterlogging of soybean cultivars. Irrig. Sci. Online: DOI 10.1007/s00271-009-0168-x. 2009.
2. Demonstrated viability of subsurface drip irrigation for Mid-South corn production. Subsurface drip irrigation (SDI) was investigated for potential water savings for Mid-South corn production. SDI can have a higher application efficiency than the more common surface methods, but has been used infrequently in humid regions like the Mid-South. Observed yields were not significantly different between treatments replacing 100% and 60% of estimated crop water use. The rainfall and thus the irrigation requirement varied by year, which is expected in the region. Similarly, the yield response varied by year. Results are important because corn production in the region is expected to increase with increased demand for ethanol fuels. Some corn producing areas are already experiencing water shortages. Although rainfall in the Mid-South is usually sufficient to produce a corn crop, production without irrigation is not recommended. Understanding the options available for irrigating will allow producers to select the optimal production system for their situation. Refereed Publication serving as basis for accomplishment: Log # 219590Bauer, P.J., Foulk, J.A., Gamble, G.R., Sadler, E.J. 2009. A comparison of two cotton cultivars differing in maturity for within-canopy fiber property variation. Crop Science. 49:651-657.