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Nonpoint Project-Supported Research, Nutrient Management Studies

Major funding contributors:

  • Department of Agriculture, Trade, and Consumer Protection (DATCP)
  • Natural Resources Conservation Service (NRCS)
  • Wisconsin Fertilizer Research Program (WFRP)
  • Wisconsin Buffer Initiative (WBI)
Nutrient losses from agricultural activities can contribute to surface and groundwater problems. Research is designed to identify the effects of soil characteristics and management practices on nonpoint source pollution. Specifically, losses of sediment, phosphorus (P), and nitrogen (N) are targeted. For a more complete list of research activities partially supported by the Nonpoint Project, click here.

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Research Methods:


Research Results:
• Soil P level directly influences P concentration in runoff.
• Wisconsin soils have different soil P - runoff P relationships.

soil test P graph 1
Relationship between soil test P level (Bray P1, 0-15 cm) and dissolved P (DP) concentration in simulated runoff for no-till and chisel plow corn systems without recent manure additions on well-drained silt loam soils at Lancaster and Arlington and on a poorly drained silty clay loam soil at Fond du Lac, 1999 to 2001. (Andraski & Bundy; 2003 J. Environ. Qual. 32:310-316).

• Phosphorus losses and the P fraction from land-applied manure are affected by tillage type and timing, season of appliation, and manure characteristics.

tillage and manure rate 1
Dissolved P (DP) load in simulated runoff immediately following the establishment of semi-solid dairy manure and tillage (NT, no-till; CP, chisel plow) treatments in spring and fall at Arlington (averaged across four studies), 1999 to 2004. (Bundy, Andraski, Powell; 2001 J. Environ. Qual. 30:1822-1828).

tillage and manure rate 1
Effect of tillage and manure rate on dissolved and total P load in simulated runoff immediately following the establishment of semi-solid dairy manure and tillage (NT, no-till; CP, chisel plow) treatments in spring at Lancaster, 2000. (Andraski, Bundy, Kilian; 2003 J. Environ. Qual. 32: 1782-1789).

• Phosphorus losses from manure are also influenced by animal diet P levels and manure water-extractable P content.

tillage and manure rate 1
Effect of the level of dietary P (LPD, low P diet; HPD, high P diet) and manure rate on dissolved and total P load in simulated runoff immediately following semi-solid dairy application in spring at Arlington, 1999. (Ebeling, Bundy, Powell, Andraski; 2002 Soil Sci. Soc. Am. J. 66:284-291).

tillage and manure rate 1
Relationship between manure (dairy semi-solid, slurry, and poultry) water-extractable P (WEP) application rate to no-till corn and dissolved P (DP) load in simulated runoff using fresh and dried-ground manure samples, Arlington, August 2004. All manure sources were applied at a 1st-year availability rate of 60 lb P2O5 /acre.

• Phosphorus losses can also occur when plant materials freeze in the field at the end of the growing season.

tillage and manure rate 1
Water-extractable P (WEP) concentrations of fresh, frozen, and dried alfalfa and grass tissue, Arlington 2001. Roberson, Bundy, Andraski; 2007 J. Environ. Qual. 36:532-539.

tillage and manure rate 1
Effect of topgrowth removal and killing (Paraquat herbicide) of alfalfa and grass tissue on dissolved P (DP) load in simulated runoff at Arlington, July 2001. Roberson, Bundy, Andraski; 2007 J. Environ. Qual. 36:532-539.

• Improved prediction of crop N needs and timing of N applications can reduce nitrate leaching losses.

tillage and manure rate 1
Relationship between the amounts of excess N fertilizer applied to corn relative to the observed optimum N rate and average soil water NO3-N concentrations from four crop management systems at Arlington, 1993 to 1995. Management systems included continuous corn with and without manure history, second-year corn following alfalfa with and without manure applied to first-year corn. (Andraski, Bundy, Brye; 2000 J. Environ Qual. 29:1095-1103).

tillage and manure rate 1
Effect of the number of years since manure and/or legumes on the decrease in the amount N fertilizer needed to achieve economically optimum corn grain yields and the resultant economic gains from two N rate recommendation methods (book-value N credits or the pre-sidedress soil NO3 test (PSNT) compared with the unadjusted base N rate recommendations, 101 corn trials in Wisconsin. (Andraski & Bundy; 2002 Agron. J. 94:1411-1418).

Research Influences Agency Nutrient Management Policy

Research results (such as those listed above) are integrated into a nutrient management planning tool SNAP-Plus and a P loss risk assessment tool Wisconsin Phosphorus Index. The Wisconsin P Index provides a field-specific estimate of the risk of P loss based on readily accessible field and soil characteristics and management practices used in the field. Examples of these characteristics and practices include soil type, slope, soil test P level, crop rotation, manure and fertilizer applications, and tillage.

Recently, P-based nutrient management planning has been adopted as an approach for minimizing P losses from farmland and increasingly incorporated into State and Federal government agency nutrient management policy and regulations. Soil Science faculty and staff participated in technical committees composed of technical experts, agency staff, agricultural professionals, agribusiness representatives, farmers, and other stakeholders to develop the NRCS Nutrient Management Standard and the WDATCP Agricultural Livestock Siting Technical Criteria. The research base on management issues and management practice effects on nutrient losses provided the foundation for the nutrient management provisions in these agency documents. The strong science base that this research provides for agency nutrient management policy is essential for ensuring the credibility and integrity of these polices. Specifically, the Wisconsin P Index was incorporated into the NRCS 590 Nutrient Management Standard Code 590 as the primary approach for P-based nutrient management planning. The 590 Standard was adopted as the technical criteria for nutrient management planning by the Agricultural Livestock Siting Technical Criteria Committee.

• Preliminary data showing a good relationship between P index values and the amounts of P in runoff from several sub-watersheds in Wisconsin provides encouraging evidence that nutrient mangement policy developed by Wisconsin agencies is sound.

tillage and manure rate 1
Relationship between the Wisconsin P Index values and measured annual total P (TP) loads in runoff from 18 sub-watersheds thoughout Wisconsin, 2003 to 2004.

Connection of Nonpoint Project and Wisconsin Buffer Initiative (WBI) Funded Research

Currently, the Wisconsin P Index does not have a mechanism for considering the effects of vegetative buffer strips on the risk of P loss. WBI projects are intensively studying buffer influences on sediment and P losses (see WBI Research). Results from these studies will be incorporated into the Wisconsin P Index so that P index values will reflect the influence of buffers on the risk of P runoff losses.


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