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The conversion of atrazine or 2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine to hydroxyatrazine was undertaken. Dechlorination proceeded at neutral pH by the soil bacterial mixed culture LFB6. 18O-labeling experiments revealed that conversion was hydrolytic, mediated by bacterial enzymes. Reaction rates were significantly rapid, indicating that small soil bacteria populations can yield considerable amounts of hydroxyatrazine.

Soils exposed to repeated spills of atrazine, alachlor, and metolachlor yield enrichment cultures containing atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) at a concentration of 100 ppm (0.46 mM) as a sole nitrogen source. More than 80% of the S-triazine ring carbon atoms are liberated as CO2-14 when ring-mineralizing activity is restored by mixing pure cultures.

The National Resource Inventory (NRI) may be used to estimate soil organic C (SOC) levels at a regional scale if accurate and precise estimates can be made across a wide range of soils, land uses, and topographic positions. The objectives of this study were (i) to identify important sources of variation in SOC content at a regional scale and (ii) to determine the precision with which SOC content can be estimated. Surface soil samples (0-10 cm) were collected in four Major Land Resource Areas (MLRAs) and analyzed for SOC, sand, silt, and clay content. Land use, hillslope position, and slope aspect effects on SOC levels were evaluated by analysis of covariance with sand or clay content as a covariate to adjust for textural differences at each sample point. Land use was a significant source of variation in all four regions. Hillslope position and slope aspect were significant sources of variation in only one of the four regions and there were no significant interactions between land use and hillslope position or aspect. The SOC content ranged from 26 to 55 Mg ha 10 [cm.sup.-1] in the Northern Mississippi Valley Loess Hills, 22 to 50 Mg ha 10 [cm.sup.-1] in the Palouse and Nez Perce Prairies, 9 to 26 Mg ha 10 [cm.sup.-1] in the Central High Plains, and 5 to 8 Mg ha 10 [cm.sup.-1] in the Southern High Plains. Standard errors ranged from 0.5 to 5.0 Mg [ha.sup.-1] and were lowest in regions where SOC levels were also lowest. Results indicate the NRI can be an effective tool for estimating SOC levels under different land use and conservation practices on a regional scale.

Diversity of soil series present in a region may hinder identification of soil quality factors and indicators at a regional scale. Our objectives were (i) to identify soil quality factors for a diverse population of soils at the regional scale, (ii) to determine which factors vary significantly with land use, (iii) to select indicators from these factors that can be used with the National Resource Inventory (NRI) for monitoring soil quality, and (iv) to compare these results to a similar study involving only a single soil series. One hundred eighty-six points representing 75 soil series in the Northern Mississippi Valley Loess Hills and 149 points representing 58 soil series in Palouse and Nez Perce Prairies were sampled from a statistically representative subset of NRI sample points and analyzed for 20 soil attributes. Factor analysis was used to identify soil quality factors and discriminant analysis was used to identify factors and indicators most sensitive to land use within each region. In the Northern Mississippi Valley Loess Hills, five soil quality factors were identified. Discriminant analysis selected potentially mineralizable N (PMN), microbial biomass C (MBC), water stable aggregates (WSA), and total organic C (TOC) as the most discriminating attributes between land uses. In the Palouse and Nez Perce Prairies, six factors were identified. Discriminant analysis selected TOC and total N as the most discriminating attributes between land uses. The soil quality factors were similar among three of the four regions, but TOC was the only indicator common to all regions for distinguishing among land uses.

Information on the probability distribution and variability of soil properties at a regional scale could improve the ability of the USDA-Natural Resources Conservation Service (NRCS) to monitor soil condition using the National Resources Inventory (NRI). Our objective was to evaluate the hypothesis that the probability distribution of 17 physical, chemical, and biological soil properties are: (i) normally distributed, or (ii) log-normally distributed at a regional scale, and to estimate the magnitude of change that may be detected assuming either a normal or log-normal distribution. Samples were collected irrespective of soil series from two Major Land Resource Areas (MLRAs) (no. 9 and 105), and from the Ascalon (fine-loamy, mixed, superactive, mesic Aridic Argiustoll) and Amarillo (fine-loamy, mixed, superactive, thermic Aridic Paleustalf) soils in MLRA 67 and 77, using the NRI sampling design. Most soil properties were non-normally distributed, with the frequency of non-normality varying between MLRAs. Confining sampling to a single soil series did not consistently improve the precision with which soil properties were estimated. [Log.sub.e] transformation resulted in normal distributions for most soil properties and reduced variability two- to threefold. However, a few soil properties remained non-normally distributed. Soil pH may be monitored at the regional scale with a high degree of precision. Small changes in soil C content (3-8% of the regional mean} may be detected using [log.sub.e] transformed total organic C as the indicator. Sampling soil properties as part of the NRI should improve NRCS' ability to monitor soil condition on a regional scale.

The article focuses on the use of aerial seeding as a means of increasing crop production in the U.S. Topics discussed include the benefits and limitations of aerial seeding, factors to be considered in employing aerial applicators and the economical aspect of the practice. Also presented are the alternative practices of seeding cover crops and areas in the U.S. that have seen an increase in aerial seeding.

Shoot-to-root communication is crucial for plant acclimation to phosphorus (P)-deficiency. Both sugars and miRNAs have been implicated as potential signal molecules transported through phloem from shoot to root for the regulation of gene expression and Pi uptake in the root. By studying the expression patterns of both a serine/threonine phosphatase gene (PvHAD1) and microRNA399 (miR399) in common bean (Phaseolus vulgaris L.), we provide evidence for the interaction between light, phloem transport, and miR399 in the systemic regulation of gene expression under P-deficiency. Especially, miR399 expression in both the shoot and the root requires photosynthetic carbon assimilation during the onset of P-deficiency. In contrast to systemic signaling, local sensing was the primary causal factor for rapid down-regulation of PvHAD1 by Pi prior to the reduction of miR399 level in P-deficient roots. Furthermore, this initial response to Pi in P-deficient root was also mimicked by the Pi analog, phosphonate (Phi). Our current findings suggest that plants have developed a highly coordinated dual regulatory pathway, namely long-distance signaling of P-deficiency from shoot to root versus local sensing of Pi in the root. [ABSTRACT FROM PUBLISHER]

White lupin (Lupinus albus L.) develops proteoid roots when grown in phosphorus (P)-deficient conditions. These short, lateral, densely clustered roots are adapted to increase P availability. Previous studies from our laboratory have shown proteoid roots have higher rates of non-photosynthetic carbon fixation than normal roots and altered metabolism to support organic acid exudation, which serves to solubilize P in the rhizosphere. The present work indicates that proteoid roots possess additional adaptations for increasing P availability and possibly for conserving P in the plant. Roots from P-deficient (–P) plants had significantly greater acid phosphatase activity in both root extracts and root exudates than comparable samples from P-sufficient (+P) plants beginning 10 d after emergence. The increase in activity in –P plants was most pronounced in the proteoid regions. In contrast, no induction of phytase activity was found in –P plants compared to +P plants. The number of proteoid roots present was not affected by the source of phosphorus supplied, whether organic or inorganic forms. Adding molybdate to the roots increased the number of proteoid roots in plants supplied with organic P, but not inorganic P. Increased acid phosphatase activity was detected in root exudates in the presence of organic P sources. Native-polyacrylamide gel electrophoresis demonstrated that under P-deficient conditions, a unique isoform of acid phosphatase was induced between 10 and 12 d after emergence. This isoform was found not only within the root, but it comprised the major form exuded from proteoid roots of –P plants. The fact that exudation of proteoid-root-specific acid phosphatase coincides with proteoid root development and increased exudation of organic acids indicates that white lupin has several coordinated adaptive strategies to P-deficient conditions. [ABSTRACT FROM AUTHOR]