Soil nutrients need to be properly managed to meet the fertility requirements of crops without adversely affecting the environment. The soil nutrients of greatest concern for protecting water quality are nitrogen (N) and phosphorus (P).
Nitrogen not used by a crop can move below the root zone, a process called leaching, and eventually contribute nitrate to groundwater. Nitrate is the most common groundwater contaminant found in Wisconsin. Nitrate levels that exceed the established drinking-water standard of 10 ppm nitrate N have the potential to adversely affect the health of infants and livestock.
Surface-water quality can be harmed with the addition of nutrients. Erosion and runoff from fertile cropland to lakes, ponds, and streams add nutrients that stimulate the excessive growth of aquatic weeds and algae. Phosphorus is the most important nutrient to prevent from reaching surface water because P stimulates excessive growth of aquatic plants and algae. This growth can result in serious consequences for lakes: It can deplete their oxygen levels, resulting in fish kills, and reduce the aesthetic and recreational values of lakes.
Nutrient management practices for minimizing water quality impacts vary widely and are dependent upon soil, cropping, topographical, weather, and economic conditions. For example, careful management of N should be a priority on sandy soils to control nitrate leaching to groundwater; minimizing runoff and erosion should be a primary goal on sloping cropland fields.
Because of the variety of factors to consider in crop fertility management, it is nearly impossible to identify best management practices applicable to all Wisconsin farms. Nutrient management practices for preserving water quality need to be tailored to the unique conditions of individual farms. This worksheet lists many agricultural practices that can influence the contribution of soil nutrients to water resources. Not all the practices described are applicable to all farms. However, completing the nutrient management assessment should allow you to prioritize management practices that need to be modified to protect the quality of nearby water resources.
How will this worksheet help?
- It will take you step by step through your nutrient management practices.
- It will help you rank your nutrient management practices according to how they may affect water quality on your farm.
- It will provide you with easy to understand rankings that will help you analyze the risk level of your nutrient management practices.
- It will help you determine which of your nutrient management practices are reasonably safe and effective, and which practices might require some modification to better protect your water resources.
The goal of Farm*A*Syst is to help you protect the groundwater that supplies your drinking water.
These terms may help you make more accurate assessments when completing this worksheet.
Ammonium forms of N fertilizers: Ammonium nitrate, ammonium sulfate, anhydrous ammonia, nitrogen solutions, urea.
Band application: A technique for applying starter fertilizer at planting. Fertilizer is applied in a band about 2 inches below and 2 inches to the side of the seed.
Broadcast application: A method of applying fertilizer in which it is uniformly spread over the surface of fields.
Composite soil sample: A soil sample submitted for testing that is an accurate representative of the sampling area (such as a cropland field). A composite sample should consist of at least five individual soil cores per 5 acres.
Cover crops: Densely seeded crops (such as rye, oats, and wheat) planted in the interim period between principal crop production to protect soil from erosion.
Highly erodible land (HEL): Cropland fields that have an erosion index of 8 or greater. Such fields are required to be farmed according to an approved conservation plan as specified in the 1985 Farm Bill (Food Security Act).
Irrigation scheduling: Planning crop irrigation frequencies and amounts based on soil, crop, climatic, and management factors.
Legume nitrogen credit: Amount of nitrogen available to a crop following a legume crop (such as alfalfa, clover, and soybeans) in the rotation. This amount of nitrogen should be deducted from the crop's base nitrogen fertilizer recommendation.
Manure nutrient content: Amount of crop nutrients available from a given unit of manure, usually expressed in pounds of nutrient (N, P 2 O 5 , K 2 0) per ton or per 1,000 gallons of manure. Determined either through manure sample analysis or use of University of Wisconsin laboratory averages (book values).
Multiple delayed applications: Nitrogen applications in which fertilizer is applied in several increments during the growing season, with none of the fertilizer being applied prior to planting.
Nitrification inhibitor: A compound added to ammonium or ammonium forming nitrogen fertilizers to slow the conversion of ammonium to nitrate, which reduces the potential for nitrogen losses that occur in the nitrate form (such as leaching and denitrification).
Nutrient credits: The amount of crop nutrients available from noncommercial fertilizer (such as manure and organic waste) applications to cropland, legumes grown in rotation with grain crops, carry over soil nitrate, and so forth. The amount of the nutrient credit is determined and then deducted from the base fertilizer recommendation. Accounting for nutrient credits can result in economic and environmental benefits.
Optimum soil test values: The mid-range of soil test values (or levels) for phosphorus and potassium. At optimum soil test values, fertilizer additions are approximately equal to the crop's nutrient use.
Routine soil testing: Analyzing of soil samples to estimate the major nutrient (nitrogen, phosphorus, and potassium) supplying capacity of a given soil as well as pH. Fertilizer and lime recommendations are based on soil test results.
Sidedress application: A method of applying fertilizer, typically nitrogen, in which it is placed next to or between crop rows during the growing season.
Soil sampling: Collecting a soil sample that will be analyzed for nutrient supplying capacity; this, in turn, leads to a fertilizer recommendation. The sample must be representative of the field from which it is collected to ensure accurate fertilizer recom-mendations.
Soil test phosphorus: Soil test value for phosphorus determined through routine soil testing. Expressed in parts per million (for-merly pounds per acre) and assigned an interpretation of either very low, low, optimum, high, or excessively high.
Soil nitrate tests: Soil tests that measure soil nitrogen and can improve the efficiency of nitrogen fertilizer applications to corn by adjusting nitrogen fertilizer recommendations for field specific conditions. Two soil nitrate tests exist in Wisconsin: a preplant and a presidedress soil nitrate test.
Split applications: Nitrogen fertilizer applications where the fertilizer is applied in several increments during the growing season.
Spreadable cropland: Cropland that is environmentally, economically, and agronomically suitable for the application of manure.
Starter fertilizer: An in row (banded) application of fertilizer placed near the seed to promote vigorous seedling growth by providing a high concentration of readily available nutrients. Starter fertilizer is most valuable on cool, wet soils.
Tolerable soil loss (T): A defined annual rate of soil erosion that if exceeded would remove soil from the landscape faster that it is being formed. One long-term effect of exceeding T rates is reduced soil productivity. Tolerable soil loss rates vary among soil types; however, the majority of rates are from 3-5 tons/acre/year.
University of Wisconsin fertilizer recommendations: Fertilizer recommendations based on soil test results and university research specific to the soils and cropping conditions found in the state of Wisconsin.
Yield goal: A criterion used in determining phosphorus and potassium fertilizer recommendations. Crop yield goals should be realistic and based on records from previous years. Yield goals should not be more than 10-15 percent above the previous 3 to 5 year average.
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The Farm*A*Syst Program is a cooperative program funded nationally by: USDA Cooperative
State Research
Education Service (CSREES), USDA Natural Resources Conservation Service (NRCS), and the
US
Environmental Protection Agency. This worksheet has been produced by the National Farm*A*Syst Office located at B142 Steenbock Library, 550 Babcock Drive, Madison, WI 53706-1293, Phone: (608) 262-0024. This worksheet is based on the original Wisconsin Farmstead Assessment Program. FarmA Syst team members: Gary Jackson, University of Wisconsin-Extension, Kim Cates, Wisconsin Geological and Natural History Survey, and Fred Madison, Wisconsin Geological and Natural History Survey and University of Wisconsin-Madison. Written by Scott J. Sturgul, senior outreach specialist, Nutrient and Pest Management Program, and Larry G. Bundy, professor of soil science and extension soil scientist, University of Wisconsin-Madison and University of Wisconsin-Extension. Technical review provided by Keith Kelling, professor of soil of soil science, University of Wisconsin-Madison and University of Wisconsin-Extension; Fred Madison, professor of soil science, Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison; Maurice Vitosh, professor of soil science, Michigan State University and Michigan State University-Extension. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, University of Wisconsin- Extension, Cooperative Extension. University of Wisconsin-Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. If you need this information in an alternative format, contact the Office of Equal Opportunity and Diversity Programs or call Extension Publications at: (608) 262-2655. |
July 24, 1998
Dennis Hoffman, Project Leader
Steve Dagitz, Webmaster