Date of Graduation

12-2017

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Haggard, Brian E.

Committee Member

Naithani, Kusum J.

Second Committee Member

Miller, David M.

Third Committee Member

Sharpley, Andrew N.

Keywords

Floodplain; Phosphorus; Release; Soils; Water

Abstract

Soils may contain large amounts of legacy phosphorus (P) due to past application of excess fertilizers, releasing P during runoff and flood events. As the level of P in soils increases, the release of P from the soils increases, but the temporal fluctuations of this release are not well known. Experiments were conducted to examine 1) the variability of soluble reactive P (SRP) release from the soil throughout a year and 2) the effect of repeated flooding and drying cycles on release rates. Soil cores were collected 7 times throughout a year from 2 sites within the Watershed Research and Education Center (WREC). Cores were inundated, water samples were analyzed for SRP, and release rates were calculated for each core. The soil was also collected and analyzed for Mehlich-III and water extractable P (WEP). SRP release rates changed significantly across seasons, but were not significantly related to Mehlich-III P (M3P) or WEP. The final set of cores was maintained in the lab for 73 days and flooded 5 times; there was no noticeable effect on SRP release.

Soils high in P should be managed so as not to become P sources to the watershed. Water treatment residuals (WTRs) have the ability to bind to P and reduce its solubility, but little research has been conducted on whether liquid WTRs would be more effective. Our objectives were to 1) determine an effective liquid WTR application rate and 2) the effectiveness of that rate when flooded repeatedly. Six liquid WTR treatments (220, 440, 1320, 2200, 3100, or 4400 kg ha-1) and a control were applied in triplicate to cores from 3 sites within WREC. Soils were flooded and SRP was analyzed in the water samples. At a rate of 440 kg ha-1, the liquid WTRs substantially reduced SRP release rates from the cores. When this rate was applied to another set of cores, release was controlled for 73 days when soil test P (STP) was less than 100 mg kg-1. With higher STP, greater quantities or repeated applications of liquid WTRs may be required.

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