|| Nebraska's MSEA project focuses on both the evaluation and demonstration of both new and available technology for water, nitrate and pesticide management on irrigated monoculture corn and corn-soybean rotations. A major goal is to develop Best Management Practices (BMPs) for water, nitrogen, and herbicide use that will reduce groundwater contamination.
The Shelton site is in the Central Platte Valley where more than 90 percent of the land is cultivated. Over 85 percent of the cropland is irrigated and more than 500,000 acres are underlain by groundwater having nitrate-nitrogen levels greater than the Maximum Containment Level of 10 parts per million (ppm).
Expansion of the contaminated area has only recently been contained, primarily as the result of an intensive producer education program. Research is concentrated on the evaluation and demonstration of farming systems and BMPs for water, nitrate, and herbicide management of irrigated corn to reduce the risk of groundwater contamination.
Many of the problems are the result of too much nitrogen and too much water with poor timing of applications. The goal of this project is to develop an integrated management system, that will reduce nitrogen movement into groundwater.
Study Objectives and Results:
Assess the projected benefits to water quality of implementing modified farming systems in the Midwest:
- Measure the impact of prevailing and modified farming systems on the content of nutrients and pesticides in ground and surface water.
- Carefully controlling the amount and timing of chemical and irrigation applications has reduced herbicide and nitrate concentrations in groundwater. Atrazine concentration has declined by 50 percent (from 3 to 1.5 parts per billion) during the life of this project. Under the sprinkler irrigation system, nitrate concentration has declined from 27 to 15 ppm in the upper part of the aquifer. A smaller but significant decline was recorded under the surge irrigation system.
- Identify and increase understanding of factors and processes that control fate and transport of agricultural chemicals.
- Spatial variability in soil N availability and/or nitrate leaching is a problem when striving to maintain productivity while reducing nitrate leaching.
- Surge-flow furrow irrigation techniques reduced water application by an average of 65 percent over a 5 year period as compared to conventional furrow irrigation methods. Center pivot irrigation reduced water application by 71 percent over the same period. These reductions in irrigation amount have substantially reduced nitrate leaching during the growing season.
Evaluate the social and economic impacts of using alternative management systems.
- Improved nitrogen (soil, testing, tissue testing, and fertigation) and water (irrigation scheduling, surge flow, and sprinklers) management practices can maintain yields and reduce N leaching to groundwater.
- Corn-soybean rotations can reduce nitrogen fertilizer use by approximately 100 pounds per acre and achieve comparable yields of irrigated corn.
- Alfalfa, some forage sorghum, and soybeans are all effective scavengers of residual nitrate in the root zone.
- Surge-flow irrigation can reduce water application by 50 percent in comparison to conventional practice in the region; sprinkler irrigation is even more efficient. Water savings are offset by greater capital investment and higher application costs.
- Producers who used more fertilizer nitrogen than University recommendations had the highest levels of nitrate in shallow groundwater and of carryover nitrate at the end of the growing season.
- Crop rotations like corn-soybean, diversify time requirements, and reduce economic risks while reducing fertilizer nitrogen and pesticide requirements.
- Transfer appropriate technology for use on the land.
- Chlorophyll meters allow producers to monitor plant nitrogen needs during the growing season and to inject nitrogen fertilizer into water (fertigation) as needed.
- Cost sharing of surge valves by the Central Platte Natural Resources District has complemented MSEA activities.
- The chlorophyll meter and fertigation were used to maximize crop use of nitrogen and phosphorous from animal wastes.
- Supplemental fertigation on 4 million acres of sprinkler irrigated cropland can save money and protect the groundwater.
- Improved nitrogen and water management technologies expand opportunities for consultants and agribusiness, who help producers make timely decisions and reduce the perceived need for nutrient, pesticide, and water applications.
- Nitrogen leaching can be reduced by using nitrification inhibitors as a management tool.
- Fertilizer nitrogen use can be reduced by using N credit for legumes in fertilizer recommendations.
- Crop advisors and consultants can help producers make economical and environmentally sound management decisions.
- Considerable progress has been made; much remains to be done. The MSEA project is developing practical management tools to help reduce the loading of nitrate to groundwater.
ARS - James Schepers, 402-472-1513
CSRS/U of Neb. - Roy Spalding, 402-472-8214
CSRS/U of Neb. - Darrell Watts, 402-472-5814
USGS - Dan Fitzpatrick, 402-437-5115
EPA - Julie Elfving, 913-551-7475
ES/U of Neb. - Kelly Wertz, 306-236-1280
NRCS - Tom Hamer, 402-437-5313