The agronomic potential of 11 South American phosphate rocks was estimated by four laboratory methods (neutral ammonium citrate with two extractions, acid ammonium citrate [pH 3], 2% citric acid, and 2% formic acid) and by crop response data obtained from a greenhouse experiment with guinea grass (Panicum maximum Jacq.) on an acid (pH 4.9) Tropeptic Haplustox (Las Gaviotas) from Colombia. Standards for comparison included triple superphosphate (TSP) and phosphate rocks from the USA (North Carolina, central Florida, and Tennessee), Tunisia (Gafsa), and Israel (Arad). The relationship between laboratory reactivity values and crop response was evaluated following three cuttings of guinea grass at four rates of P application. Almost no yield was obtained without added P, and significant differences were observed between response curves of the P sources. Based on both solubility as measured by the four methods identified and crop response data, the 11 phosphate rocks were found to be segregated into four groups representing high (Bayovar), medium (Huila and Pesca), low (Sardinata, Patos de Minas, Lobatera, Araxá, and Abaeté), and very low (Catalão, Jacupiranga, and Tapira) reactivity. Solubility in neutral NH+4 citrate was found to be the most accurate of the chemical procedures tested. The relationship between yield and source solubility in neutral NH+4 citate showed that all of the sedimentary sources were more reactive than the igneous or metamorphic sources.

There has been a significant decrease in the number of preschool children with elevated blood lead levels (BLL), from 88.2 to 4.4 per 10,000 children over the last three decades as shown by National Health and Nutritional Examination Survey (NHANES) data. However, there are still certain high-risk populations that have not been well studied. One such group is that of pregnant women. During pregnancy, BLL tends to increase due to greater bone turnover, which causes release of lead stored in bone. This increase may not affect the pregnant woman's health directly but could be extremely harmful to the rapidly developing central nervous system in the fetus as it crosses the placenta easily. This current study was undertaken to estimate the prevalence of elevated BLL in pregnant women in a community hospital, monitor the effect of routine preventive practices on maternal BLL, and to elucidate the relationship between maternal and neonatal BLL and their anthropometric indices. A retrospective chart review was conducted on all hospital deliveries occurring in the first six years after the initiation of universal blood lead screening of pregnant women (n=6880). The prevalence of elevated lead (> or =10 microg/dL) in our patient population was 1.7%. The factors associated with elevated lead levels were recent immigration to the US, poor socioeconomic status and low educational levels. Simple interventions such as hand washing as well as calcium and iron supplementation significantly reduced maternal BLL from 16.82+/-9.5 to 11.48+/-9.3 microg/dL (P<0.0001). A significant correlation (r=0.4, P<0.007) is present between the post-intervention but not the pre-intervention maternal BLL and the neonatal BLL. Given the vulnerability of the developing fetal brain and that CNS complications are associated with elevated lead levels, antenatal lead screening should be part of routine prenatal care. Simple preventive measures may play a role in decreasing maternal BLL and thereby decreasing transplacental transfer of lead to the fetus.

A study was made of the effect of partial acidulation of rock phosphate, coating with elemental S, granule size, placement, and soil pH on yield and uptake of P and S by ryegrass grown on Miami (pH 6.7) and Dubuque (pH 6.0 and 7.0) silt loams in the greenhouse. In most cases, both yield and P uptake increased with each increase in level of acidulation; however, the results for the 50 and 100% levels were quite similar. Total P recovery by the ryegrass was highly correlated with the percentage of total P that was available (water soluble plus citrate soluble) in the fertilizer. Mixing of the granules with the soil gave higher yields and P recovery than banding, and the 10‐ to 20‐mesh granules were generally more effective than the 5‐ to 10‐mesh size on the soil at pH 6.0. Coating of the granules with elemental S gave no significant increases in yield but increased P recovery significantly from the 5‐ to 10‐mesh granules in several cases. Both yield and P uptake for rock phosphate were higher at pH 6.0 than 7.0.