1 / 8

Wisconsin P Index: Assessing Soluble P Losses from Cropped Fields

This study from the University of Wisconsin-Madison calculates average dissolved P losses in runoff for cropped fields using two P sources: DP released from soil surface and DP released from fertilizer on the surface. The study provides an example of P loss assessment in a somewhat poorly drained silt loam field near a stream. The estimation involves factors like soil test P, fertilizer application, runoff volume, and precipitation. The Wisconsin P Index model is tested with field data and proves to be effective in estimating dissolved P losses. Current research is focused on further testing management and soil effects on runoff volume.

tasya
Download Presentation

Wisconsin P Index: Assessing Soluble P Losses from Cropped Fields

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wisconsin P Index Approach to Assessing Soluble P Losses from Cropped Fields L.W.Good Department of Soil Science University of Wisconsin Madison

  2. Average Dissolved P (DP) Losses in runoff are calculated for each crop year for two P sources: • DP released from soil surface • DP released from fertilizer on surface

  3. Example Field Somewhat poorly drained silt loam 1% slope Within 300 feet of stream Soil test P = 35 ppm Bray1 P Year 1: Corn grain, Fall chisel plowed, spring disking, Maintenance fertilizer (DAP) incorporated by tillage spring. Year 2: Soybean, Maintenance fertilizer (DAP) broadcast spring Year 3: Winter wheat, Maintenance fertilizer (DAP), broadcast fall

  4. DP from Soil = Surface Soil Test P (STP)x P Extraction Coefficient x Runoff (RO) Volume x Units Conversion FactorSurface STP = Plow layer STP x Stratification FactorMaintenance Fertilizer P = Crop P Removal, so plow layer soil test P not expected to change year-to-year, but surface soil test P will change with tillage.

  5. DP from Fertilizer =Fertilizer P on surface X Runoff/Precipitation x O.034 exp (3.4 Runoff/Precip) The ratio Runoff/Precipitation is for the season of application and can be thought of as the potential for precipitation water to runoff, rather than infiltrate

  6. Total Estimated Average Annual Dissolved P Losses in Runoff for Example Field

  7. WI P Index “Modeling” Approach • Tested with field runoff data • Shown to be providing a good estimate of field runoff dissolved P losses when measured runoff volume and precipitation are used in the equation • Current work on Wisconsin P Index focusing on testing methods of assessing management and soil affects on average runoff volume

  8. Vadas -- APLE 2.4

More Related