Liming poultry manures to decrease soluble phosphorus and suppress the bacteria population.

Stabilizing phosphorus (P) in poultry waste to reduce P losses from manured soils is important to protect surface waters, while pathogens in manures are an emerging issue. This study was conducted to evaluate CaO and Ca(OH)2 for killing manure bacterial populations (pathogens) and stabilizing P in poultry wastes and to investigate the influence on soils following amendment with the treated wastes. Layer manure and broiler litter varying in moisture content were treated with CaO and Ca(OH)2 at rates of 2.5, 5, 10, and 15% by weight. All treated wastes were analyzed for microbial plate counts, pH, and water-soluble phosphorus (WSP), while a few selected layer manures were analyzed by phosphorus X-ray absorption near edge structure (XANES). A loamy sand and a silt loam were amended with broiler litter and layer manure treated with CaO at rates of 0, 2.5, 5, 10, and 15% and soil WSP and pH were measured at times 1, 8, and 29 d. Liming reduced bacterial populations, with greater rates of lime leading to greater reductions; for example 10% CaO applied to 20% solids broiler litter reduced the plate counts from 793,000 to 6500 mL-1. Liming also reduced the WSP in the manures by over 90% in all cases where at least 10% CaO was added. Liming the manures also reduced WSP in soils immediately following application and raised soil pH. The liming process used successfully reduced plate counts and concerns about P losses in runoff following land application of these limed products due to decreased WSP.

Differential Sensitivity of Phytophthora parasitica var. nicotianae and Thielaviopsis basicola to Monomeric Aluminum Species.

ABSTRACT Aluminum (Al) is toxic to many plant pathogens, including Thielaviopsis basicola and Phytophthora parasitica var. nicotianae. Because fungi-toxicity of Al has been described in soils over a wide pH range, multiple species of Al may be responsible for pathogen suppression. The goals of this work were to determine the sensitivity of T. basicola and P. para-sitica var. nicotianae to Al over a range of pH values, quantify the toxicity of monomeric Al species to production of sporangia of P. parasitica var. nicotianae and chlamydospores of T. basicola, and detect the accumulation of Al in pathogen structures. A complete factorial treatment design was used with Al levels ranging from 0 to 100 muM and pH levels ranging from 4 to 6 in a minimal salts medium. The chemistry of test solutions was modeled using GEOCHEM-PC. Colonies were grown in 5% carrot broth, and after 1 or 2 days, the nutrient solution was removed, colonies were rinsed with water, and Al test solutions were added to each of four replicate plates. After 2 days, propagules were counted and colonies were stained with the Al-specific, fluorescent stain lumogallion. The oomycete P. parasitica var. nicotianae was sensitive to multiple monomeric Al species, whereas sensitivity of T. basicola to Al was pH-dependent, suggesting that only Al(3+) is responsible for suppression of this fungal pathogen. Chlamydospore production by T. basicola was inhibited at pH values <5.0 and Al levels >20 muM, whereas sporangia production by P. parasitica was inhibited at Al levels as low as 2 muM across all pH values tested. The lumogallion stain was an effective technique for detection of Al in fungal tissues. Aluminum accumulated in sporangia and zoospores of P. parasitica var. nicotianae and in nonmelanized chlamy-dospores of T. basicola, but not in cell walls of either organism. The differential sensitivity of the two organisms may indicate that true fungi respond differently to Al than members of the oomycota, which are more closely related to plants.

Bonding of Hg(II) to reduced organic sulfur in humic acid as affected by S/Hg ratio.

Organic matter is an important sorbent of heavy metals in soils and sediments. The heterogeneity of organic matter, including the presence of various reactive O-, N-, and S-bearing ligands, makes it difficult to precisely characterize the nature of metal-ligand binding sites. The objective of this research was to characterize the extent and nature of Hg(II) bonding with reduced organic S in soil organic matter. Sulfur-rich humic acid (0.7 +/- 0.1 mol of S kg-1) was extracted from samples of surface soil from a marine wetland. Synchrotron X-ray absorption near-edge structure (XANES) analysis at the S K edge indicated that 70 +/- 3 mol % of the organic S was in a reduced oxidation state. Aqueous solutions containing 2 mmol of Hg kg-1, 0.1 M NaNO3, and humic acid added at various S/Hg molar ratios at pH 5.60 +/- 0.02 were characterized using extended X-ray absorption fine structure (EXAFS) spectroscopy at the Hg LIII edge. Spectral fitting showed that as the total S/Hg ratio increased from 0.6 to 5.6 (reduced S/Hg of 0.4-4.0), the fraction of Hg-S bonding relative to Hg-O (or Hg-N) bonding increased from 0.4 to 0.9. Results demonstrated preferential bonding of Hg(II) to reduced organic S sites and indicated that multiple sulfur ligands were coordinated with Hg2+ ions at high S/Hg ratios, which corresponded to low levels of complexed Hg(II).

Nonphytotoxic Aluminum-Peat Complexes Suppress Phytophthora parasitica.

ABSTRACT Amendment of peat-based potting media with Al(2)(SO(4))(3) suppresses damping-off of Vinca (Catharanthus roseus) caused by Phytophthora parasitica. The species of aluminum (Al) responsible for disease suppression have not been identified. The objective of this study was to determine the effects of amount and pH of Al(2)(SO(4))(3) amendment solutions on survival of P. parasitica. In separate experiments, peat was amended with Al(2)(SO(4))(3) solutions adjusted to pH 4 or 6 at either 0.0158 or 0.0079 g of Al per gram of peat. Amended peat was placed in Büchner funnels maintained at -2.5 kPa matric potential. Peat was infested with P. parasitica by placing zero, two, or five colonized Vinca leaf disks in each funnel, and 15 Vinca seeds were placed in each funnel. After 24 h, the matric potential was brought to 0 kPa to induce zoospore release and returned to -2.5 kPa after 24 h. Pathogen populations and stand counts were assessed after 2-week incubation. Al amendment solutions at both pH 4 and 6 reduced pathogen populations at 0.0158 g of Al per gram of peat. Solutions at pH 4 reduced pathogen populations by more than 90% at both inoculum levels; amendment solutions at pH 6 reduced populations by 95% at the low inoculum level and 65% at the high inoculum level. The prevalence of Al(OH)(2)(+) in peat amended with Al(2)(SO(4))(3) solution at pH 6 suggests that ions other than Al(3+) may be responsible for pathogen suppression. Based on the difference in chemical conditions of Al-amended peat and suppressive mineral soils, the mechanism of Al-mediated suppression of plant pathogens is speculated to be different in the two systems. Peat containing Al-peat complexes was chemically suppressive to P. parasitica and may confer Al-mediated suppression of plant pathogens with a nonphytotoxic form of Al.

Formation of chloropyromorphite in a lead-contaminated soil amended with hydroxyapatite.

Conversion of soil Pb to pyromorphite [Pb5(PO4)3Cl] was evaluated by reacting a Pb contaminated soil collected adjacent to a historical smelter with hydroxyapatite [Ca5(PO4)3OH]. In a dialysis experiment where the soil and hydroxyapatite solids were placed in separate dialysis bags suspended in 0.01 M NaNO3 solution a crystalline precipitate, identified as chloropyromorphite, formed on the dialysis membrane containing the soil. The aqueous composition of the solution indicated that dissolution of solid-phase soil Pb was the rate-limiting step for pyromorphite formation. Addition of hydroxyapatite to the soil caused a decrease in each of the first four fractions of sequential extractable Pb and a 35% increase in the recalcitrant extraction residue. After a 240-d incubation at field-moisture content there was a further increase in the recalcitrant extraction residue fraction of the hydroxyapatite-amended soil to 45% of the total soil Pb. The increase in the extraction residue fraction in the hydroxyapatite amended 0-d incubated soil as compared to the control soil illustrates that the chemical extraction procedure itself caused changes in extractability. Thus, the chemical extraction procedure cannot easily be utilized to confirm changes occurring in amended soils. The further increase after the 240-d incubation implies that the reaction also occurs in the soil during incubation. Extended X-ray absorption fine structure (EXAFS) spectroscopy indicated that after the 240-d incubation the hydroxyapatite treatment caused a change in the average, local molecular bonding environment of soil Pb. Low-temperature EXAFS spectra (chi data and radial structure functions--RSFs) showed a high degree of similarity between the chemical extraction residue and synthetic pyromorphite, providing additional evidence that the change of soil Pb to pyromorphite is possible by simple amendments of hydroxyapatite to soil.

The ras-related GTPase rac1 regulates a proliferative pathway selectively utilized by G-protein coupled receptors.

Ras and rac are each members of the superfamily of monomeric GTPases and both function as molecular switches to link cell-surface signals to intracellular responses. Using a novel assay of cellular proliferation called R-SAT (Receptor Selection and Amplification Technology), we examined the roles of ras and rac in mediating the proliferative responses to a variety of cell-surface receptors. Activated, wild-type and dominant-negative mutants of rac and ras were tested for their effects on cellular proliferation either alone or in combination with receptors. Activated rac (rac Q61L, henceforth rac*) and ras (ras G12V, henceforth ras*) each induced strong proliferative responses. Dominant-negative rac (rac T17N, henceforth rac(-)) dramatically suppressed proliferative responses to G-protein coupled receptors (GPCR's) including the m5 muscarinic receptor and the alpha1B adrenergic receptor. In contrast, rac(-) had little or no effect upon responses to the tyrosine kinase receptor TrkC, and only partially suppressed responses to the Janus kinase (JAK/STAT) linked granulocyte macrophage colony stimulating factor (GM-CSF) receptor. Dominant-negative ras (ras T17N, henceforth ras(-)) blocked the proliferative responses to all of the tested receptors. Compared to rac(-) and ras(-), wild-type rac and ras had only modest effects on the tested receptors. Overall these results demonstrate that rac mediates the proliferative effects of G-protein coupled receptors through a pathway that is distinct from the proliferative signaling pathway utilized by tyrosine kinase linked and JAK-linked receptors.