Nickel (Ni) is one of many trace metals widely distributed in the environment. High concentrations of Ni in soils and aquifers have been observed worldwide, causing several potential human health impacts. Better understanding of Ni transport in soils and aquifers is necessary to assess and remediate insitu environmental contamination. The movement of Ni in soils and aquifers is highly dependent on adsorption-desorption reactions in the solid phase. In this study, kinetic batch, sequential extractions, and miscible displacement experiments were conducted to investigate the effect of several of environmental factors including soil type, reaction time and competing ions, on the fate of Ni in soils. In addition, forward and inverse modeling efforts were made to mathematically predict the reactivity of Ni transport in soils. Based on batch study results, adsorption of Ni was highly nonlinear and strongly kinetic. The comparison of Ni sorption on soil followed the sequences: Windsor < Olivier < Webster, which was related to soil propertities (CEC, clay content, pH and organic matter). Desorption of Ni from all soils were hysteretic in nature which is an indication of lack of equilibrium retention and/or irreversible or slowly reversible processes. A sequential extraction procedure provided evidence that a significant amount of Ni was irreversibly adsorbed on all soils. Moreover, a multi-reaction model (MRM) with equilibrium, kinetic and irreversible sorption successfully described the adsorption kinetics of Ni in Windsor, Olivier and Webster soils and was capable of predicting the desorption of Ni from these soils. Column transport experiments indicated strong Ni retardation followed by slow release or extensive tailing of the breakthrough curves (BTCs). We evaluated several MRM formulations for prediction capability of Ni retention and transport in soils and concluded that nonlinear reversible, along with a consecutive or concurrent irreversible reactions were the dominant mechanisms. The use of batch rate coefficients as model parameters for the predictions of Ni BTCs underestimated the extent of retention and overestimated the extent of Ni mobility for all soils. When utilized in an inverse mode, the MRM model provided good predictions of Ni BTCs and the distribution of Ni with soil depth in soil columns. In natural soil and water environments the competition between Ni and Cadmium (Cd) has the potential of increasing Ni mobility and bioavailability. Our results from batch experiments demonstrated that rates and amounts of Ni adsorption by these soils were significantly reduced by increasing Cd additions. The presence of Cd in soils increased mobility of Ni in columns as well as forced Ni sorption at higher affinity (or specific sorption) sites. The simultaneous presence of Ni and Cd also changed the distribution of Ni and Cd from an accumulation pattern to a leaching pattern in Olivier soil column, which has the potential risk of contamination of ground water.

The bioavailability and fate of Zinc (Zn) in soils is influenced by reactions occurring at the water-mineral interface. Understanding Zn interaction with mineral surfaces is essential to the understanding of Zn fate and toxicity. In this study, adsorption experiments investigated the impact of ligands and pH on the adsorption of Zn to mineral surfaces. X-Ray Absorption Fine Structure Spectroscopy (XAFS) was used to elucidate the adsorption mechanisms of Zn to mineral surfaces as impacted by ligands. Impact of ligands on Zn adsorption was dependent on mineral type and pH of the system. XAFS analysis showed that adsorption mechanisms of Zn were impacted by pH and ligand presence. In the ferrihydrite system, Zn adsorption was enhanced in presence of citrate and phosphate (PO4), reduced in presence desferrioxamine (DFO-B), and reduced in presence of humic acid (HA) at pH>6.0. XAFS analysis showed that Zn formed strong linkages with high affinity edge sites of ferrihydrite in the control and in presence of enhancing ligands (citrate and PO4), whereas formed weaker, low affinity linkages in presence of supressing ligands (DFO-B and HA). From an environmental perspective, Zn was more likely to be desorbed from the ferrihydrite surface in the presence HA and DFO-B. In the kaolinite system, Zn adsorption was reduced in presence of citrate and DFO-B, and increased in presence of HA. Zn formed inner sphere complexes at pH 5.5 in the control and in presence of ligands. At pH 7.5, a Zn-Al layered double hydroxide was formed in the control, that was absent in presence of any ligand, suggesting that ligands suppress the formation of Zn-Al LDH in kaolinite. In the mixed ferrihydrite-gibbsite system, Zn adsorption was enhanced in presence of all ligands, excluding DFO-B. Adsorption mechanisms of Zn to ferrihydrite were unaffected by ligand presence. The impact of organic matter (OM) degradation on heavy metal distribution in sewage sludge was investigated. Cu, Pb and As were bond with the OM fraction of sludge, whereas Zn was bond to Fe/Mn oxide fraction. OM degradation increased mobility and bioavailability of Zn and Cu, whereas it had less impact on Pb and As.

The spatial and temporal variation of soil properties was evaluated on three sites in close proximity to Bayou Wikoff, St. Landry Parish, Louisiana. A total of 1,068 surface (0-5 cm) samples were collected, geo-located, and transported to Louisiana State University for physical and chemical analyses. Physical and chemical properties were spatially and temporally displayed using ArcGIS. Interpolation techniques such as spline, kriging, and inverse distance weighting were evaluated to determine the best fit model for the project. Spline and inverse distance weighting were found to be the least accurate interpolation models. Kriging provided the most accurate model of spatial and temporal data distribution. Clay content (for total suspended solid control), P levels, and organic C % were a primary focus for this study, as potential non-point source pollution threats to water quality in Bayou Wikoff. All three sites were evaluated individually, as each had unique management practices. Pasture Site 1 exhibited larger concentrations of nutrient deposition proportional to increasing organic C % and clay content in areas of lower elevation. These areas were nearest to the bayou and potentially allowed for runoff, reducing water quality. Pasture Site 2 has artificial swale formations that affected the distribution of the evaluated properties. Extensive research at this site exhibited patterns of nutrient distribution that correlated with the swale formations. In the low portion of the swale, clay content, organic C %, and corresponding nutrient concentrations increased. The Pristine Site, used as a control site, showed evidence that the surface soil (0-5cm) was heavily altered from natural deposition as a result of being turned, moved, or replaced. Overall, spatial and temporal assessments revealed that while the three sites have unique distribution patterns of clay and organic C %, the soils are not hazardous for water quality. However, best management programs should focus on swales and low lying areas to determine the affect of spatial variability.

Cotton (Gossypium spp.), the most important textile fiber crop in the United States (US), is cultivated in 17 states across the southern US. and a very important agricultural commodity for several states. The use of hybrids in the US has been limited due to seed cost production. The objective of this study was to investigate a novel method for the production of F2 cotton hybrids using honey bees as pollinators and Roundup Ready® gene as selection trait. This research was conducted during three years (2005-2007) in Louisiana. Crosses between non-transgenic and transgenic varieties were made in 2005 to obtain F1 cottonseeds using honey bees. In 2006, F2 cottonseed was obtained. In 2007, F1, F2, and parents were field tested using a randomized complete block design with 3 replications in two locations. Data analysis was conducted using the SAS PROC MIXED procedure with estimates of means generated using least square means (LS means). Results indicate that all crosses exhibited heterosis in the F1 hybrid populations relative to the best parent. The crosses LA1110023/PHY410R and ARKRM24-12-04/PHY410R exhibited a higher degree of heterosis for yield averaging 33.1% and 20.6%, respectively, across locations. Yield heterosis in the F2 population was of 20.9% and 19.5%, respectively, and statistically different from the best parent. The ARK9506-40-05/PHY410R cross had yield heterosis averaging 15.6% in the F1 population and 13.5% in the F2 population; however, these were not significantly different from the best parent. The lack of significant yield heterosis might be attributed to experimental error and suggests the need for further field testing. Fiber quality descriptors from the six crosses, did not have a significant heterosis in the F2 population relative to the best parent. In summary, the use of herbicide resistant varieties as males and Roundup Ready® gene as selection trait, conventional varieties as females and honey bees as pollinators, has proven to be a viable method for developing F2 hybrid varieties. Further variety testing will be required to determine the best combination of parents. Promotion of this technology among seed companies is required for the development of better and improved cotton varieties as F2 hybrids.

Damaging and often irreversible effects occurring in aquatic ecosystems have recently been linked to the presence of pharmaceuticals in water bodies. Because this crisis has only recently been identified, existing reports on the consequences of this contamination are scarce. In EPA standard acute effluent toxicity tests, Ceriodaphnia dubia, Daphnia pulex, Pimephales promelas, Mysidopsis bahia, and Menidia beryllina were subjected to two of the most widely distributed pharmaceuticals in the U.S., ethinyl estradiol (EE2), a synthetic form of estrogen, and fluoxetine HCl (FLX), the active ingredient in Prozac®, for 96 hours to assess and evaluate toxic responses. After test termination, mortality curves were statistically analyzed to quantify 96 hour median effective concentrations (EC50s), no observable effect concentrations (NOECs), lowest observable effect concentrations (LOECs), and chronic values (Ch.V.s). Derived EC50s for both drugs identified C. dubia as the most sensitive organism. In terms of the Ch.V., C. dubia was the most sensitive organism administered EE2 and M. bahia given FLX. The most resilient species was P. promelas regarding the EC50 after EE2 dosing, D. pulex in respect to the Ch.V. after EE2 dosing, and M. beryllina pertaining to the EC50 and Ch.V after FLX dosing. Existing risk assessments and traditional toxicity tests do not incorporate sublethal effects. Because EE2 and FLX have the potential to alter serotonin, dopamine, and estrogenic hormones, biological activities encompassing these chemicals could be affected such as changes in behavior, growth and development, and fecundity. Observations on exposed organisms indicate that there were sublethal effects. The observed increases in abnormal behaviors of exposed organisms included unresponsiveness, irregular swim patterns, erratic activity, and convulsions with observed decreases in feeding habits and aggression. Ethinyl estradiol appeared to accelerate maturation; elevated concentrations appeared to slightly stimulate maturity while appearing to inhibit molting. The organisms exposed to higher concentrations of EE2 and FLX seemed to lack pigment. Continuous environmental pollution of these unregulated chemicals can cause stress on aquatic ecosystems and result in disturbances of the normal development and life cycles of aquatic organisms. If these sublethal disruptions in biological activity continually disregarded, catastrophic destructions of entire ecosystems could transpire.

Research conducted over two years evaluated EPTC at 2.0, 2.9, 3.9, and 4.9 kg ai/ha incorporated on pre-formed sugarcane beds using a Lilliston® rolling cultivator and a hipper/bedder. Averaged across EPTC rates 30 days after application, bermudagrass was controlled 62% when incorporated with a rolling cultivator compared with 43% for the hipper/bedder. For johnsongrass and purple nutsedge, incorporation implements were equally effective and control with EPTC 30 days after application averaged 49 and 30%, respectively. Averaged across incorporation methods, control of all weeds 30 days after EPTC application was maximized at 3.9 kg/ha, but control was no greater than when applied at 2.0 kg/ha (45% bermudagrass, 57% johnsongrass, and 33% purple nutsedge control). EPTC treatments were followed by glyphosate at 2.24 kg ai/ha and weed control was compared with a glyphosate alone program consisting of two applications of glyphosate at 2.24 kg ai/ha. Where EPTC was applied 60 days earlier and followed by one application of glyphosate, weed control was no greater than when glyphosate was applied twice (bermudagrass ground cover no more than 5% and johnsongrass control at least 88%). In contrast, purple nutsedge was controlled 31 to 40% where EPTC was followed by one application of glyphosate compared with 63% for two applications of glyphosate. An economic analysis of EPTC and glyphosate programs was performed using herbicide costs and variable costs associated with operation of incorporation implements and herbicide application. Cost of EPTC at 2.0 kg/ha plus application and incorporation would be $38.36/ha with the rolling cultivator and $49.33/ha for the hipper/bedder. Where EPTC at 2.0 kg/ha is followed by glyphosate as Roundup Original Max®, total cost would be $18.66/ha more than where generic glyphosate is used. For EPTC at 2.0 kg/ha incorporated with a rolling cultivator and followed by generic glyphosate, total cost would be $15.31/ha more compared with generic glyphosate applied twice. In other research, EPTC applied at 2.9 to 6.8 kg/ha and incorporated at planting did not negatively affect sugarcane shoot population 35 and 186 days after planting compared with standard herbicide treatments. EPTC was ineffective on grass and broadleaf winter weeds.

Reasons for the gradual genetic yield improvement (21-31 kg ha-1yr-1) reported for soybean [Glycine max (L.) Merr.] during decades of cultivar development are not clearly understood. Identification of mechanisms for the yield improvement would aid in providing indirect selection criteria for streamlining cultivar development. Our objective was to identify yield components, growth parameters, phenological data, and/or other agronomic data responsible for yield improvement in 18 public southern cultivars released between 1952 and 2000. The study was done at the Ben Hur research farm near Baton Rouge, LA (300N Lat) during 2007 and 2008. Experimental design was a randomized complete block with four replications and one factor (cultivar). Data were obtained on yield, seed per area, seed size, seed per pod, pod per area, pod per reproductive node, reproductive node number per area, percent reproductive nodes, node number per area, total dry matter (TDM) at R7 and harvest index (HI). Data were analyzed sequentially at primary (seed number per area and seed size affecting yield), secondary (pod number per area and seed per pod effecting seed number per area), tertiary (pods per reproductive node and reproductive node number per area affecting pod number per area) and quaternary levels (node number per area and percent reproductive nodes affecting reproductive node number per area). Yield improvement among these cultivars was not related to length of the seed filling period, or days from emergence to R5 or R7. Neither was lodging resistance involved. Greater yield in new vs. old cultivars was mainly due to greater TDM (R7) (71%) and secondarily to higher HI (29%). Yield components responding to greater dry matter accumulation to create more yield in new vs. old cultivars were node and reproductive node number per area, pod number per area and seed number per area. A possible indirect selection criterion for yield during cultivar development is reproductive node number per area.

Field research was conducted from 2006 to 2009 to study Texasweed [Caperonia palustris (L.) St. Hil.] interference and management in Cocodrie rice. Texasweed interference at 10 plants/m2 caused 24 to 31% rice yield reduction. The maximum possible yield loss was estimated to be 81%. Rice yield reduction was primarily due to a reduction in culms/m2 and filled grains per panicle. For maximum yield, Texasweed must be removed by two weeks after emergence and managed until permanent flood establishment. Shade had no effect on Texasweed emergence but significantly reduced growth and reproduction. At 100 days after emergence, 50, 70, and 90% shade reduced dry matter per plant by 31, 47, and 90%, respectively. Texasweed height increased with increasing shade up to 70% and then decreased. After 28 DAI, Texasweed height in 70% shade increased 15 to 21% compared with 0% shade. Texasweed seemed to mitigate the adverse effect of shade on growth by increasing specific leaf area and leaf biomass. In a flood depth study, Texasweed plants were able to survive and produce seeds in flood depths up to 30 cm; however, growth and fruit production were reduced. A 76 and 41% reduction in total dry matter per plant was recorded for Texasweed flooded at two- to three-leaf and four- to five-leaf stage, respectively. Increasing flood depths resulted in an increase in plant height and greater biomass allocation to the stem. Texasweed plants produced adventitious roots and a thick spongy tissue, secondary aerenchyma, in the submerged roots and stem, which may play a role in its survival under flooded conditions. For Texasweed control, bensulfuron-methyl interacted synergistically with both penoxsulam and bispyribac-sodium. Bensulfuron-methyl, therefore, can be mixed with either penoxsulam or bispyribac-sodium to improve Texasweed control. V-10142 provided excellent PRE and EPOST activity on Texasweed. V-10142 at 224 g ai/ha by itself, applied to four- to five- leaf Texasweed, was not effective but improved Texasweed control when mixed with bispyribac-sodium at 29 g ai/ha or penoxsulam at 40 g ai/ha.

Methods to control thatch layers in mature turfgrasses have relied on sand-topdressing and/or mechanical removal. Mechanical removal of thatch through vertical mowing and aerification is effective but disruptive to playing surfaces compared to sand topdressing. As a result, many turf managers have opted to implement sand-topdressing regiments as their primary method for reducing thatch buildup. This research was conducted to 1) determine the effect of cultivar on thatch decomposition and 2) examine the effect of sand topdressing on thatch microenvironment and decomposition. Sand topdressing treatments consisting of sterilized or non-sterilized sand applied at 0.4 cm 14 d-1 or as a single application at 1.2 cm and an untreated control to two hybrid bermudagrasses (Cynodon dactylon L.), Tifway and Celebration from May to September in 2008 and 2009. At the initiation of the experiment, Celebration had twice the thatch layer of Tifway. The only treatment that reduced thatch was sand applied every 14 d-1 reduced thatch 21% to 34% and 20% to 30% for Tifway and Celebration, respectively. In contrast, a single sand topdressing application led to net accumulations of 20% to 30% compared to accumulations of 29% to 38% increases in untreated plots. Sand applied more frequently resulted in higher microorganism populations and had no detrimental effect on turfgrass quality. Routine sand applications increased thatch relative humidity (RH) compared to untreated controls for both hybrid-bermudagrass cultivars. Laboratory experiments were conducted to examine the effect of temperature, 20 C and 30 C, and RH (80%, 90%, 95%, >99%) on Tifway and Celebration thatch decomposition. Increasing temperature and RH resulted in 189% to 397% increase in microbial degradation. Failure to provide adequate moisture reduced microbial activity and led to declines of 170% to 243% in decomposition when thatch was subjected to drying conditions. Because thatch tissue composition and response to changes in temperature and RH were similar between cultivars, newer more vigorous hybrid-bermudagrass such as Celebration will require a frequent sand topdressing regiment in conjunction with mechanical removal for acceptable thatch control.

Indeterminate and determinate soybean (Glycine max (L). Merr.) cultivars were treated with the harvest aids, paraquat and sodium chlorate, when moisture of seed collected from the uppermost four nodes of plants averaged 60, 50, 40, 30, and 20% (+ or - 2%). Harvest aid application at 60% seed moisture reduced yield of the Maturity Group (MG) IV indeterminate cultivar 15%, but yield was not affected with application at 50% seed moisture. For MG V and MG VI determinate cultivars, application at 60 and 50% seed moisture reduced yield 4 to 22%, but yield was not affected when harvest aid was applied at 40% seed moisture. Soybean treated with harvest aid was harvested 8 to 15 days before the non-treated. The value of paraquat harvest aid was also evaluated when used in fungicide and insecticide IPM programs. Fungicide (pyraclostrobin plus thiophanate-methyl at R3) application increased soybean green leaf retention, green stems, and seed moisture. Failure to control stink bug resulted in increased green pods, seed moisture, and seed damage. Application of harvest aid decreased green leaf retention, green stems, and seed moisture. When harvest aid was applied and stink bug was not controlled, seed quality deductions for moisture, foreign material, and damage were < $63.10/ha. When stink bug was controlled at the maximum level (acephate plus cyfluthrin when population reached 2 to 3 per 25 sweeps) or the intermediate level (lambda-cyhalothrin when population reached threshold of 8 to 9 per 25 sweeps), deductions were < $30.24/ha. When harvest aid was not applied, seed quality deductions across all fungicide/stink bug control programs were 3.8 to 6.4 times greater than when harvest aid was applied. Increase in net return due to harvest aid was greatest when fungicide was applied and stink bug was controlled at either level ($171.49 and $169.89/ha) and lowest when fungicide was not applied ($94.81 and $78.49/ha). Even so, net returns were more than enough to offset the cost of a paraquat harvest aid application. At a second location, net returns, regardless of harvest aid application, tended to be highest when fungicide was applied and when stink bug was controlled.