Impact of Organic Phosphorus Sources on Phosphorus Runoff
Adriane L. Elliott Department of Soil and Crop Sciences
Why Study Phosphorus?
P is the limiting nutrient for algal and aquatic plant growth in surface water bodies. ¾ Phosphorus (P) is the nutrient that often
promotes hyper-eutrophication (Sharpley et al., 1994).
Nutrient Sources in the S. Platte Basin
Where Do the Nutrients Come From? Manure
Fertilizer Phosphorus Nitrogen
Wastewater Treatment Plants 0
50
100
150
Thousands of Tons per Year Data from USGS NAWQA study.
Manure P vs. Cropland P Use
< 25% 25 - 50% 50 - 100% >100%
Map from LPES curriculum by Rick Koelsch, Univ. of Nebraska-Lincoln
Percentage of CO Feedlots of Different Sizes 5%
4%
32000
Location of Feedlots in CO
Nutrient Runoff Fate Nutrients leave feedlot
Decaying algae and aquatic plants consume dissolved oxygen
Water quality decreases for plant, animals, and humans
Phosphorus Loss
Increased surface soil P concentrations intensify P loss in runoff (Hesketh et al., 2000). ¾P • • •
transport mechanisms Runoff Erosion Leaching 9 Occurs less in heavy soils
Published P Research
Simulated rainfall research has established relationships among: ¾ Dairy manure application rate and soil test P
concentration (Bray-1) (Motschall and Daniel, 1982). ¾ Soil test P concentration (Mehlich-3) and dissolved reactive P (DRP) (Sharpley et al., 1994).
Justification and Objective I
No field research has focused on the effect of source on P runoff. We investigated runoff, both chemically and physically, from agricultural plots that were amended with raw, composted and vermicomposted dairy manure. ¾ Results were compared to control that received
no P additions.
Justification and Objectives II
The literature suggests: ¾ ¾
Little dissolution of rock P (RP) in alkaline, calcareous soils (Robinson et al., 1992). Singram et al. (1995) concluded that RP was 65% as effective as single-super phosphate in a soil with pH 8.05 29 days after application.
“Micronized RP” claimed to dissolve and become plant available in alkaline soil. Objectives were: ¾ ¾
To determine if the RP treatment provided plants with adequate P over a two year growth trial. Quantify P concentration leaving plots amended with RP.
Site Background
Colorado State University Horticulture Field Research Center Soil: Kim heavy clay loam (fine-loamy, mixed, calcareous, mesic Ustic Torriorthents) 1% slope Total field size was 0.4 hectare (1 acre)
Results: Baseline Soil Samples
¾ All blocks rated low in soil test P concentration ¾ Field texture was a clay loam ¾ pH across field averaged 7.75 ¾ Field had a high EC averaging 3.2 mmhos cm-1 ¾ Low K and Zn concentrations across field Property pH EC (mmhos cm-1) OM (mg g-1) NO3-N (mg kg-1) AB-DTPA P (mg kg-1) K (mg kg-1) Zn (mg kg-1) Fe (mg kg-1) Mn (mg kg-1) Cu (mg kg-1) Texture
