Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
ANIMAL SCIENCES
Non Technical Summary
Dairy-manure accumulation in soils can result in phosphorus-related degradation of water quality. Phosphorus in these soils can be mobile after years of site abandonment and conditions normally associated with high phosphorus stability. This continuous release of phosphorus to surface water bodies results in substantial delay in recovery of water quality even when current loads are reduced. This project will address the potential of manure-derived components to affect the long-term stability of phosphorus in manure-impacted soils. Effects of three manure derivatives will be studied: magnesium, dissolved organic C (DOC), and noncrystalline silica. If manure additions cease, would phosphorus stabilize when inhibiting components are lost or transformed? Can dietary manipulation help reduce inhibiting components and thus improve phosphorus stabilization? We plan to (i) test the inhibiting effects of magnesium, manure-derived DOC, and noncrystalline silica; (ii) compare
active and abandoned dairy sites with respect to calcium phosphate crystallinity; and (iii) determine phosphorus retention properties of noncrystalline silica. Surface horizons of intensive areas will be sampled. Separation techniques will be used to isolate and identify the manure components and study their behavior and stability in the presence and absence of inhibitors. The goal is to bridge gaps in understanding of components linking animal nutrition and nutrient management, and hence enable more effective strategies to sustain both dairy farms and the environment.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
1. To determine the effects of Mg-, DOC-, and Si activities on the crystallization of Ca-P forms in the presence and absence of the noncrystalline-Si clay from manure and manure- impacted soils. 2. To compare Ca-P crystallinity between representative samples of active-dairy soils, abandoned-dairy soils, and dried dairy manure. 3. To determine P retention characteristics of noncrystalline Si clay from manure and manure-impacted soils, as influenced by pH and saturating cation.
Project Methods
Samples from A horizons will be collected from intensive areas of four active and four abandoned dairies within the Lake Okeechobee basin. Samples will be collected from randomly- selected locations within respective sampling areas. Fresh manure samples will be obtained from the active dairy sites. Also, information will be compiled about pertinent dietary practices at active dairies. Separation of noncrystalline Si clay will be accomplished by particle-size and density fractionations. We will concentrate dissolved organic C (DOC) directly from manure-contaminated soils via leaching, filtration, coagulation, decanting of ion-rich solutions, and re-dissolution in distilled water. The reconstituted solutions will be adjusted to the C content of the leachates and used to evaluate effects of DOC on Ca-P crystallization. We will collect leachate from representative surface soil layers by leaching at weekly intervals at 0.4 mL per min simulated rainwater under suction.
Leachates will be analyzed for Ca, Mg, Na, K, Al, Fe, and Si. Activities of ion species will be calculated using a computer solution speciation model. Experiments will be performed to determine if crystallization of Ca-P in the higher-density fraction can be enhanced by systematic elimination of suspected inhibitors, Mg, DOC, and noncrystalline Si. Mineralogical analysis of high-density separates of silt and clay from each sample, and of selected low-density separates, will be accomplished by x-ray diffraction and other solid-state techniques. Abundant amounts of noncrystalline Si will be available from the lower-density fractions of clay from the samples studied. Materials from the four active dairies will be used for P-retention and surface-properties analyses. These materials will have already had organic matter removed. They will further be extracted with sodium citrate-dithionite-bicarbonate and 0.5 M HCl to remove any non-Si components remaining. Relation between surface charge
and pH, along with points of zero salt effect and points of zero net charge, will be determined for noncrystalline-Si separates. P-sorption isotherms will be performed on these noncrystalline-Si separates following saturation with Na, Ca, or Al. The critical comparisons to be made using these data are between (i) active-dairy, abandoned-dairy, and manure materials; and (ii) incubated solids from the treatments. We will conduct statistical assessment of XRD peak-intensity ratios and differences between leachate solution composition of active and abandoned dairies. Applicable information developed in this research on diet-related factors that affect P migration in soils will be developed into extension publications and made available on a website. The information will also be delivered to nutritional consultants, veterinarians, feed industry personnel, and dairy farmers through meetings and personal contacts. Current courses offered at the University of Florida that address nutrient
management and environmental issues will also incorporate knowledge derived from this study.