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Phosphate treatments can reduce metal dissolution and transport from contaminated soils. However, diammonium phosphate (DAP) has not been extensively tested as a chemical immobilization treatment. This study was conducted to evaluate DAP as a chemical immobilization treatment and to investigate potential solids controlling metal solubility in DAP-amended soils. Soil contaminated with Cd, Pb, Zn, and As was collected from a former smelter site. The DAP treatments of 460, 920, and 2300 mg P kg-1 and an untreated check were evaluated using solute transport experiments. Increasing DAP decreased total metal transported. Application of 2300 mg P kg-1 was the most effective for immobilizing Cd, Pb, and Zn eluted from the contaminated soil. Metal elution curves fitted with a transport model showed that DAP treatment increased retardation (R) 2-fold for Cd, 6-fold for Zn, and 3.5-fold for Pb. Distribution coefficients (Kd) increased with P application from 4.0 to 9.0 L kg-1 for Cd, from 2.9 to 10.8 L kg-1 for Pb, and from 2.5 to 17.1 L kg-1 for Zn. Increased Kd values with additional DAP treatment indicated reduced partitioning of sorbed and/or precipitated metal released to mobile metal phases and a concomitant decrease in the concentration of mobile heavy metal species. Activity-ratio diagrams indicated that DAP decreased solution Cd, Pb, and Zn by forming metal-phosphate precipitates with low solubility products. These results suggest that DAP may have potential for protecting water resources from heavy metal contamination near smelting and mining sites.

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Bermudagrass [Cynodon dactylon (L.) Pers.] hay production is integral to manure management on southeastern swine farms. But swine effluent timing must be synchronized with crop nitrogen (N) demands to decrease the potential for soil N accumulation and nitrate (NO(3)) leaching. Field studies were conducted on a Prentiss sandy loam (coarse-loamy, siliceous, semiactive, thermic Glossic Fragiudult) to determine N-use efficiency (NUE) and residual soil NO(3)-N. Two rates of 10 and 20 cm yr(- 1) ( approximately 260 and 480 kg ha(-1) N, respectively) were applied in four timing treatments: April to September (full season), April to May, June to July, and August to September. Plots were harvested every 7 to 9 wk beginning in June, and soil was sampled in fall after a killing frost and the following spring. Annual uptake of N and P were least in the August to September timing treatment. Doubling the effluent rate increased N uptake 112% in 2000 (from 130 to 276 kg ha(-1)) and 53% in 2001 (from 190 to 290 kg ha(-1)), suggesting 10-cm did not meet crop N demands. Due to low rainfall and decreased forage yield in 2000, doubling the effluent rate led to increased soil NO(3)-N to 30-cm depth in fall 2000 and spring 2001. Averaged across timing treatments, soil NO(3)-N at 5-cm depth ranged from 8.5 mg kg(-1) in non-irrigated controls to 39.6 mg kg(-1) with 20-cm effluent. Results indicate low NUE in the order of 30 to 38% for applications in August to September increase the risk to surface and ground water quality from excess N remaining in soil.

Areas of intensive poultry production are prone to high phosphorus (P) losses due to excessive manure application. Historically, manure application rate has been calculated based on nitrogen (N) needs of the crops and N content of the manure with no attention to the quantity of phosphorus (P) loading. In many instances, a gradual buildup of P in soil has resulted from longterm manure application. Therefore, P input from animal manure via runoff is acknowledged as the primary factor for the eutrophication of surface water bodies. This study was conducted to evaluate (i), the impact of dietary P concentration on the broiler manure P content and the pre-analysis drying methods on the broiler manure nutrient composition with emphasis on phosphorus 2783 ORDER REPRINTS and (ii), to compare the use of Ion Chromatography and the Murphy -Riley method for the determination of inorganic phosphorus in the broiler manure water extract. Four drying methods were used to dry the fresh broiler manure as follows: air drying (AD), freeze drying (FD), oven drying at 658C (OD65), and oven drying at 1058C (OD105). The results were compared with analysis of the fresh broiler manure with no drying (ND). The diet P concentration did not affect the broiler manure total N content. However, a significant decrease in total N occurred at all P levels due to drying when compared with fresh manure analysis. The diet P level had significant effect on total P and water-extractable P. Freeze drying followed by OD105 caused the most reduction in manure total P content. Drying also had a significant effect on the metal nutrient content of the broiler manure. However, the effect was inconsistent.

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