WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2002NY2B
Title: Predicting Dissolved Phosphorus Losses in Overland Flow in Northeastern U.S.
Project Type: Research
Focus Categories: Non Point Pollution, Nutrients, Surface Water
Keywords: Dissolved Phosphorus, Nutrient management, runoff
Start Date: 03/01/2002
End Date: 02/28/2003
Federal Funds: $0
Non-Federal Matching Funds: $16,983
Congressional District: NY 26
Problem: The U.S. Department of Agriculture (USDA)-Natural Resources Conservation Service (NRCS) adopted a policy on May 24, 1999 that requires the use of a P index or other vulnerability assessment technique when developing NMP for concentrated animal feeding operations (CAFOs) and for other farms near P sensitive reservoirs, lakes and streams (Lander, 1999). A major limitation in the implementation of the P index for the NMP is the poor scientific understanding of the transport of the dissolved P in the runoff water from agricultural and forests lands. Most past research on the fate of P in the agricultural landscape was directed towards supplying P to crops for optimal growth. Moreover, it was assumed that P loss in runoff was only in the particulate form because of the strong P adsorption properties of most soils. However, many recent studies have confirmed the findings of Hergert et al. (1981) that it is not only particulate P (PP) that is lost but that also dissolved P (DP) is a significant part of the total P losses in the agricultural runoff water. Consequently, improved understand-ing of the amount of DP loss in runoff will greatly enhance prediction techniques for the P loss such as the P index method. Better understanding of DP losses will also help in the selection of effective best management practices (BMP).
Methods: The experimental methods and set-up are derived from a study in which the upland component of the Rose and Hairsine model was validated (Heilig et al., 2001; Gao et al., 2002).
In this study, we found that the Rose and Hairsine model predicted very well the concentration of sediment in the runoff water (Figure 1) by assuming that the fine particles loosened by the rain splash are removed preferentially in the runoff water resulting in a shield of coarse particles near the surface with a depth of approximately 1 cm.
The hypothesis is that the loss of the fine particles due to raindrop splash is similar to the loss of the DP from this surface layer due to raindrop impact.
The experimental apparatus is, in principle, very simple and is designed to isolate the soil, climate, and landscape factors that contribute to the P loss in runoff water. Rainfall is simulated using a computer controlled rainmaker that oscillate simultaneously along two orthogonal tracks. Each experiment will consist of carefully establishing a flat soil surface with a predetermined amount of ponded water followed by application of rain.
Only a selected set of the climate, soils, and landscape factor interaction can be done within a year¡¯s time. In the first two experimental sets, the mechanisms that contribute to the P loss in the runoff water will be quantified and the results will be used to adapt the Rose and Hairsine upland erosion model for DP loss. Consequent experimental sets will address the various factors.
Objectives: The overall goal of this project is to improve P loss prediction techniques for variable source saturated areas located in the agricultural landscape. The particular goal is to systematically derive the predictive relationship for the concentration of DP in the runoff water based source factors such as soil type and the amount and type of P in the soil, climatic factors including rainfall amount and energy, and landscape factors involving initial moisture content, ponding depth and rate of upward and downward flux. The project will ultimately lead to sounder P index tools for the unique soils and conditions in the Northeast, an improved understanding of P fate and transport processes, and improved decision making regarding P control and management practices applicable to these conditions.