Forty-two years impact of chemical fertilization on soil phosphorus partition and distribution under rice-based cropping systems.

Understanding of soil phosphorus (P) transformation is crucial to minimize its edge-of-field loss associated with ecosystem disservices. A sequential chemical extraction procedure was used to assess the impact (42 years) of organic and chemical fertilizations on soil P partition and distribution under subtropical rice based cropping systems. Experimental treatments were control, N, NP, NK, NS, NZn, NPK, NSZn, NPKSZn, and N+FYM (farmyard manure). Composite soils were collected from 0-5, 20-25 and 40-45 cm depths, extracted, and analyzed for soluble P, NaHCO3-P (inorganic and organic), NaOH-P (inorganic and organic), acid soluble (H2SO4), and residual P fractions. The NPKSZn significantly increased the concentration of soil inorganic P compared to other treatments. When FYM was applied together with N fertilizer, the organic P concentration increased, which was statistically identical to NPKSZn and NPK treatments. While the labile (NaHCO3-Pi, NaOH-Po), residual, and total P concentrations were stratified at 0-5 cm depth, the concentration of NaHCO3-Po, NaOH-Pi, and acidic P fractions increased with soil depth. The soluble, NaHCO3 (Pi and Po), NaOH-Pi and NaOH-Po, acidic, and residual P fractions constituted about 0.4, 6.6, 1.7, 21.3, 37.7, and 8.3%, respectively, of the total P. A higher concentration of the labile P at the surface soil indicated that the impact of chemical fertilization stratified the available P for plant uptake or susceptible to edge-of-field loss. The NPKSZn and N+FYM both had higher NaHCO3-Po and NaOH-Po concentrations within 40-45 cm and 0-25 cm depths, suggesting that N+FYM could promote the transformation of non-labile P into labile P pool, by reducing P fixation by soil and transport them at 20-45 cm depth. It is concluded that long-term fertilization increased the concentration of P pools especially labile P by saturating the soil adsorption sites especially in surface soil.

Dairy manure and tillage effects on soil fertility and corn yields.

Organic amendments have received renewed attention to improve soil fertility for crop production. A randomized complete block split plot experiment was conducted to evaluate the dairy manure (DM) amendments of soil for corn (Zea mays L. cv. Monsanto 919) production under different tillage systems. Main plot treatments were no-till (NT), conventional tillage (CT), and deep tillage (DT), and subplot treatments were chemical fertilization (DM(0)), and DM at 10Mgha(-1)yr(-1) (DM(10)) and 20Mgha(-1)yr(-1) (DM(20)) with supplemental chemical fertilization. Results show that tillage and DM had significantly reduced bulk density (rho(b)) with greater porosity (f(t)) and hydraulic conductivity (K(fs)) than soils under NT and DM(0). Manuring was effective to improve soil physical properties in all tillage treatments. While manure significantly increased C sequestration, the N concentration was influenced by both tillage and manure with significant interaction. The CT significantly increased P as did the addition of manure. However, with manure, K was significantly increased in all tillage treatments. While tilled soils produced taller plants with higher grain yields, and water-use efficiency than NT soils, manuring, in contrast, increased corn harvest index. Manure exerted significant quadratic effect on corn biomass N and K uptake. The variable effects of tillage and dairy manuring on soil properties and corn growth are most probably related to "transitional period" in which soil ecosystems may have adjusting to a new equilibrium.

Carbaryl, 2,4-D, and Triclopyr adsorption in thatch-soil ecosystems.

Thatch development in intensively managed turf sites may cause environmental concerns for greater sorption or leaching of applied chemicals in terrestrial ecosystems. To determine the adsorption potential of Carbaryl (1-Napthyl N-methylcarbamate), 2,4-D (2,4-dichloro-phenoxyacetic acid), and Triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) in turf ecosystems, composite thatch and underlying soil samples from three-and six-year-old stands of cool-season Southshore creeping bentgrass (Agrostis palustris Huds.) and warm-season Meyer zoysiagrass (Zoysia japonica Steud.) were collected. The samples were processed and analyzed for total organic carbon (COrg); extractable (CExt), humic (CHA) and fulvic acid (CFA); anthrone reactive nonhumic carbon (ARC) fractions; and CHA and CFA associated iron (Fe) contents. Pesticide adsorption capacity (Kf) and intensity (1/n), organic carbon partition coefficient (KOC) and Gibbs free energy change (deltaG) were calculated for thatch materials and the underlying soils using a modified batch/flow technique. Both bentgrass (BT) and zoysiagrass thatch (ZT) contained a greater concentration of CExt, CFA, CHA, and ARC than the respective soils (BS and ZS). The CExt, CFA, CHA, and ARC concentration was higher in BT compared with ZT. The BT contained a greater concentration of bound Fe in both CFA and CHA fractions than in BS, whereas ZT had more bound Fe in CHA fraction than in ZS. On average, the BT had a greater concentration of bound Fe in CExt, CFA, and CHA fractions than in the ZT. Among the pesticides, Carbaryl had higher Kf and 1/n values than 2,4-D and Triclopyr for both thatch and soil. Although the KOC and deltaG values of Carbaryl were higher in both BT and ZT than in the underlying soils, the KOC and deltaG values of 2,4-D were significantly higher in BS and ZS than in the overlying thatch materials. The 2,4-D and Triclopyr had higher leaching indices (LI) than Carbaryl for both BT and ZT materials than the respective soils. The Carbaryl, however, had a higher LI for soils than for thatch materials. Averaged across thatch materials and soils, COrg accounted for 96, 85, and 84% variations in Carbaryl, 2,4-D, and Triclopyr adsorption, respectively. Among the COrg fractions, lignin followed by CFA and CHA accounted for greater adsorption of pesticides, especially Carbaryl. The concentration of CHA and CFA bound Fe did not correlate with Kf and 1/n values of pesticides.

Development of a fluorescence polarization-based diagnostic assay for equine infectious anemia virus.

The control of equine infectious anemia virus (EIAV) infections of horses has been over the past 20 years based primarily on the identification and elimination of seropositive horses, predominantly by a standardized agar gel immunodiffusion (AGID) assay in centralized reference laboratories. This screening for EIAV-seropositive horses has been to date hindered by the lack of a rapid diagnostic format that can be easily employed in the field. We describe here the development of a rapid solution-phase assay for the presence of serum antibodies to EIAV based on fluorescence polarization (FP) (patent pending). Peptides derived from antigenic regions of EIAV core and envelope proteins were initially screened for their utility as probes in an FP assay to select the best peptide antigen candidates. The FP assay was optimized to detect the presence of EIAV-specific antibodies by a change in the FP of a fluorescein-labeled immunoreactive peptide diagnostic antigen. The most sensitive and specific peptide probe was a peptide corresponding to the immunodominant region of the EIAV transmembrane protein, gp45. This probe was tested for its reactivity in the optimized FP assay with 151 AGID-positive horse sera and 106 AGID-negative serum samples. The results of these studies demonstrated that the FP assay reactivity correlated with reported AGID results in 106 of 106 negative serum samples (100% specificity) and in 135 of 151 positive serum samples (89.4% sensitivity). The FP assay was also found to have a very low background reactivity and to readily detect antibodies produced early in infection (

Alterations in cell membrane permeability by the lentivirus lytic peptide (LLP-1) of HIV-1 transmembrane protein.

Previously we reported that synthetic peptide homologs of an amphipathic region (designated the lentivirus lytic peptide, or LLP-1) near the carboxy terminus of HIV-1 transmembrane protein (TM) were toxic for both prokaryotic and eukaryotic cells when added exogenously to cell cultures. We postulated that these peptides may exert their toxic effects in much the same manner as natural cytolytic peptides such as magainins, cecropins, and melittin by forming pores through cellular membranes. Here we show the results of 51Cr-release assays and membrane flux measurements of peptide treated cells that support our hypothesis. We have also tested a limited panel of LLP-1 peptide analogs in these assays and found that relatively minor alterations in peptide charge or amphipathicity in the parent HIV LLP-1 sequence resulted in total loss of membrane perturbative properties. These results demonstrate that the peptide homolog of HIV-1 LLP-1 can indeed perturb membranes by forming pores of defined size in cytoplasmic membranes. Furthermore, the analog studies described here reveal that the amphipathy and high positive charge of this protein segment are required for the membrane perturbative properties.