Estimating soil phosphorus requirements and limits from oxalate extract data.

Excessive fertilizer and manure phosphorus (P) inputs to soils elevates P in soil solution and surface runoff, which can lead to freshwater eutrophication. Runoff P can be related to soil test P and P sorption saturation, but these approaches are restricted to a limited range of soil types or are difficult to determine on a routine basis. The purpose of this study was to determine whether easily measurable soil characteristics were related to the soil phosphorus requirements (P(req), the amount of P sorbed at a particular solution P level). The P(req) was determined for 18 chemically diverse soils from sorption isotherm data (corrected for native sorbed P) and was found to be highly correlated to the sum of oxalate-extractable Al and Fe (R2 > 0.90). Native sorbed P, also determined from oxalate extraction, was subtracted from the P(req) to determine soil phosphorus limits (PL, the amount of P that can be added to soil to reach P(req)). Using this approach, the PL to reach 0.2 mg P L(-1) in solution ranged between -92 and 253 mg P kg(-1). Negative values identified soils with surplus P, while positive values showed soils with P deficiency. The results showed that P, Al, and Fe in oxalate extracts of soils held promise for determining PL to reach up to 10 mg P L(-1) in solution (leading to potential runoff from many soils). The soil oxalate extraction test could be integrated into existing best management practices for improving soil fertility and protecting water quality.

A microcosm study on remediation of explosives-contaminated groundwater using constructed wetlands.

Anaerobic degradation of TNT and TNB in gravel systems was rapid and similar to removal rates in parrot feather lagoons. Planted and unplanted anaerobic gravel systems were the only treatments that provided significant reduction of RDX and HMX. Planted systems with parrot feather had no effect on removal rates of explosives in anaerobic gravel systems. Reciprocating wetlands were not effective in biodegrading RDX or HMX, but were very efficient at removing COD. A scaled-up concept for bioremediating contaminated groundwater can be envisioned with the data obtained in the current study. The effectiveness of anaerobic gravel systems indicate an anaerobic subsurface-flow constructed wetland can be established as the primary treatment for remediation with C added to the influent or step fed down the length of the wetland. Another option would be to add compost as a more permanent source of C to the gravel substrate. With time, the need for C supplementation may be reduced with the C exudates and redox lowering potential of certain plants like canarygrass (Phalaris arundinacea). As a secondary treatment, a reciprocating wetland would appear to be a logical choice to quickly remove C released in effluent waters of the anaerobic wetland.

Chemical characterization and bioavailability of phosphorus in water-insoluble fractions of three mono-ammonium phosphate fertilizers.

Elemental impurities in mono-ammonium phosphate (MAP) fertilizers, such as Fe, Al, Ca, Mg, and F, result in compounds other than NH4H2PO4. The phosphorus availability of the impurity compounds was determined in 3 commercial MAP fertilizers produced from North Carolina, Florida, and Idaho phosphate rocks. Soluble compounds, including NH4H2PO4, were washed out of the fertilizers, and the water-insoluble fraction was collected. The North Carolina, Florida, and Idaho MAP fertilizers contained 13, 16, and 17% water-insoluble fractions, respectively. Availability of phosphorus in each MAP fertilizer and water-insoluble fraction was determined in a greenhouse pot study using sorghum-sudangrass (Sorghum bicolor) as the test crop. There were no differences in dry matter weights or phosphorus uptake between reagent grade MAP and each MAP fertilizer. Lower dry matter weights and phosphorus uptake were produced from the water-insoluble North Carolina, Florida, and Idaho fractions (NC greater than FL greater than ID). Chemical analysis and characterization with optical microscopy, infrared spectroscopy, and X-ray diffractometry indicated 77.3, 73.8, and 73.6% NH4H2PO4 in the North Carolina, Florida, and Idaho MAP fertilizers, respectively. MgAl(NH4)2H(PO4)2F2, AlNH4HPO4F2, and FeNH4(HPO4)2 were identified as water-insoluble phosphorus compounds. There was a significant negative correlation between the percent phosphorus present as MgAl(NH4)2H(PO4)2F2 and the phosphorus availability. Increased crystallinity of the various water-insoluble compounds also contributed to reduced phosphorus availability.

Availability of phosphorus in bone meal.

Two commercially available bone meal products (grades 0-12-0 and 6-12-0) were examined. Samples were prepared according to AOAC method 2.007, and total and available phosphorus contents were determined. Portions of these preparations were reground to pass through successively smaller sieves, and subsequent analyses indicated the availability of phosphorus to be directly proportional to fineness of grind. A quantity of the citrate-insoluble fraction of the bone meal was obtained by following AOAC extraction procedures. Agronomic studies were conducted that compared this insoluble fraction with the original bone meal material and with reagent grade Ca(H2PO4)2.H2O. The data indicated poor correlation between the analytically defined and agronomically determined availability of phosphorus.

Quinazoline CB 3717 and CB 3703 inhibition of folate retention and metabolism in Ehrlich ascites carcinoma cells and some organs of the host-mouse.

Disturbances in folate metabolism in Ehrlich ascites carcinoma-bearing mice caused by 2 quinazoline-antifolates are described. They are manifested by diminished retention in tumour cells and the host-liver of injected radioactive folate and by a decreased extent of its conversion to coenzymatic, polyglutamate forms. Kidney retention of folate was also affected by either quinazoline, showing a severalfold decrease in mice treated with CB 3703, and a 2-fold increase in those treated with CB 3717. Kidney folylpolyglutamate content was also greatly reduced.