Biomedical subjects

J L Havlin

Publications and source records attributed to J L Havlin.

2 recordsLinked to original sources

PubMed2006

Change in soluble phosphorus in soils following fertilization is dependent on initial Mehlich-3 phosphorus.

There is a lack of information on how fertilization and initial Mehlich-3 phosphorus (M3P) interact to affect water soluble P (WSP) in soils. Our objectives were to (i) quantify the relationship between WSP and M3P for four textural diverse benchmark soils of North Carolina (NC) and (ii) quantify the change in WSP concentrations following P additions to soils over a wide range of initial M3P. Soils known to represent a wide range in M3P were collected from an Autryville loamy sand (loamy, siliceous, subactive, thermic Arenic Paleudults), Wasda muck (fine-loamy, mixed, semiactive, acid, thermic Histic Humaquepts), Georgeville silt loam (fine, kaolinitic, thermic Typic Kanhapludults), and Pacolet sandy clay loam (fine, kaolinitic, thermic Typic Kanhapludults) and analyzed for M3P, Fe, Al, and WSP. An incubation study was also conducted where four samples representing a range in M3P from each series were fertilized at rates of 150 and 300 kg P ha(-1), and WSP was measured at 1, 7, and 21 d after fertilization. The Wasda muck exhibited a change point at 115 mg P kg(-1) across a broad range of M3P concentrations (60-238 mg kg(-1)) while Autryville, Georgeville, and Pacolet series (with ranges in M3P of 32-328, 119-524, 0-1034 mg P kg(-1), respectively) maintained linear relationships between WSP and M3P. For the fertilized soils, significant increases in WSP occurred regardless of P rate. Yet, WSP concentrations were greater in soils with greater initial M3P. Thus, these data suggest that shifting animal waste applications to fields of relatively lower M3P concentrations would have an immediate impact on reducing risk for P losses, if all other factors are equal.

Animals↗

PubMed2004

Technical basis for quantifying phosphorus transport to surface and groundwaters.

Decreasing the potential delivery of phosphorus in fertilizers or animal waste to surface and groundwater requires a knowledge of phosphorus's fate and transport mechanisms. The USDA Natural Resources Conservation Service has recently mandated each state to develop an assessment tool to estimate P transport to water bodies. The objective of this paper is to describe the processes involved with P transport to surface and groundwaters that must be accounted for in practical methods used to quantify the potential for P loss. Mechanistic models to assess P loss should account for: 1) P adsorbed to eroding sediments, 2) soluble P in runoff water, 3) soluble P in leaching water, and 4) P losses related to specific P sources. With sediment-bound P, the adsorbed P content in the eroded soil mass at the field edge must be quantified, whereas runoff volume and P concentration are needed to estimate soluble P loss in runoff water. Estimating P leaching potential requires calculation of drainage water volume and P concentration. When P is applied in animal waste, the specific source influences both soluble and particulate P loss because of differences in P solubility between waste types. In addition, the effects of conservation practices and other technologies on decreasing sediment, soluble, and leached P need to be included. Using these methods, a practical, quantitative P loss assessment tool can be developed that will enable technical service providers and other practitioners to estimate potential P loss and design best-management practices for land-applied waste management systems in order to minimize P transport to surface and groundwater.

Adsorption↗