Heavy metal contamination is a major concern for soil and water quality. To quantify their potential hazard, it is crucial to understand their mobility and retention in soils. The source of the problem is anthropogenic activities such as mining, smelting, usage of sewage sludge and fertilizers. The objective of this study was to quantify Cd, Cu and Pb transport and retention in three soils having different properties, and evaluate their competitive influence on the mobility of individual heavy metal. The second objective was to quantify Cd, Cu and Pb retention kinetics in the different soils. This study also investigates the extent and distribution of retained Cd, Cu and Pb with depth in soil columns. In the study, batch experiments were carried out for different range of concentrations in time. The results indicated that retention of Cd, Cu and Pb in Windsor, Mahan and Webster soil is nonlinear. Lead exhibited highest retention among all three metals. Moreover, all three metals exhibited highest affinity in Webster soil, which has a higher clay content (mostly smectite), organic material and cation exchange capacity. Sorption of all metals was also observed to be kinetic when retention time increased from one day to seven days. Miscible displacement experiments in saturated soil columns were also carried out in two ways. In the first type, consecutive pulses of Cd, Cu and Pb were sequentially introduced to each soil column followed by an extended period of leaching with the background solution (KNO3, 0.005M). In the second type, two consecutive pulses of mixed solution (Cd, Cu and Pb), each followed by leaching with the background solution, were introduced to soil columns. Results indicate that Cd was the most mobile with the highest recovery the effluent solution, whereas Pb was the least mobile with the lowest recovery among all elements and soils. It was also observed that Pb resulted in enhanced mobility of both Cd and Cu . Efforts to describe results from the column experiments based on a multirection and transport model (MRTM) showed varied degrees of success. Although the models accounts for several sorption mechanisms including nonlinear equilibrium, kinetics, and irreversible reactions, the model was not successful in predicting the competitive behavior of heavy metals in the soil columns.

Field studies were conducted in 2011, 2012, and 2013 near Alexandria, LA to determine glufosinate rates and timings for control of rhizome johnsongrass [Sorghum halepense (L.) Pers.] in glufosinate-resistant soybean [Glycine max (L.)Merr.]. Johnsongrass control (75%) and height reduction (63%) throughout the season were greatest when glufosinate was applied at 0.7 kg ai ha-1 followed by (fb) 0.6 kg ha-1. Furthermore, following initial applications of glufosinate at 0.7 kg ha-1 (2670 kg ha-1) increased soybean yields were observed compared to 0.5 kg ha-1 (2400 kg ha-1), and soybean yields were greater following sequential glufosinate applications of 0.6 kg ha-1 followed by 0.5 kg ha-1. These data suggest that sequential applications of glufosinate is an option to control rhizomatous johnsongrass in glufosinate-resistant soybean. Additionally, field trials were conducted in 2011 and 2012 to assess control of johnsongrass in soybean with sequences of chlorimuron, clethodim, and fomesafen applied at early-post-emergence (EPOST), mid-postemergence (MPOST), and late-postemergence (LPOST). Sequential applications of glufosinate was added as a comparison treatment at all three timings. Clethodim applied EPOST was similar in johnsongrass control to sequentially applied glufosinate 35 days after LPOST. Johnsongrass control at harvest following sequential glufosinate applications (90%) or clethodim fb chlorimuron fb fomesafen (82%) did not differ. At harvest, differences in johnsongrass heights were not observed between treatments. Following sequentially applied glufosinate soybean yields were similar where clethodim was applied LPOST. Furthermore, trials were conducted to assess johnsongrass control in cotton [Gossypium hirsutum L.] in 2011, 2012, and 2013 following glufosinate applied two or three times sequentially, initiated 2, 3, or 4 wk after planting and sequential applications timed 2 or 3 wk apart. Johnsongrass control was maximized when three applications were applied at least 3 wk apart. However, johnsongrass control and reduction in heights was greatest when timing the initial application 4 WAP. Additionally, cotton yield was comparable to three total applications when two applications were made initiated 4 WAP.

The potential usage and benefits of native perennial grasses (NPG) in urban plantings may be severely hindered during establishment by high weed pressure. Two studies were conducted with the objectives of examining the tolerance of several NPG to commonly available herbicides during vegetative establishment; and comparison of establishment vigor of NPG in Louisiana when weed control is implemented. The first study was conducted in greenhouse conditions to evaluate tolerance of broomsedge (Andropogon virginicus L.); blue grama (Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths); Virginia wildrye (Elymus virginicus L.); switchgrass (Panicum virgatum L.); little bluestem (Schizachyrium scoparium (Michx.) Nash); and Indiangrass (Sorghastrum nutans (L.) Nash) established 6 weeks from plugs to applications of pendimethalin; sulfosulfuron; imazapic; triclopyr; or fenoxaprop. Overall, fenoxaprop was the most injurious to NPG and slowed tillering on affected species compared to controls. Plants treated with imazapic, triclopyr, or sulfosulfuron varied in tolerance among species as well as timing of application relative to temperature. Pendimethalin was consistently the least injurious to NPG. In the second study, the same NPG species were evaluated for establishment vigor in Baton Rouge, Louisiana and Fort Polk near Leesville, Louisiana over a 12-month period with pendimethalin applied at initial planting in October 2011 and again in March 2012. At the Baton Rouge site, little bluestem and broomsedge had the highest canopy coverages of 97.7% and 100% and corresponding biomasses 156.8 and 244.8 g at the conclusion of the 12-month establishment period along with the lowest weed encroachment of 1.7%. Little bluestem and broomsedge also achieved the highest canopy coverages and biomasses at the Fort Polk site, but overall NPG establishment was slower compared to NPG establishment in Baton Rouge. Environmental factors such as soil texture, fertility, and rainfall between the two locations affected NPG establishment. Results indicate herbicide applications at least during the first year of NPG vegetative establishment may be necessary to reduce weed competition in order to establish NPG in disturbed urban sites. Species selection, herbicide selection and application, and site characteristics must be accounted for when establishing NPG in urban areas.

Field experiments in 2013 evaluated residual herbicide effects on ball (Trifolium nigrescens viv.) and white (Trifolium repens L.) clover. For the October planting, averaged across clovers, ground cover for 2,4-D plus aminopyralid and 2,4-D plus picloram averaged 4.4 and was less than for the nontreated (7.0). For the November and March plantings, ground cover for all herbicides was equivalent to the nontreated. Averaged across clover species and planting date, herbicide treatments except 2,4-D plus aminopyralid (4) resulted in ground cover 49/112 days after planting (DAP) equal to the non-treated (5.7). Lowest plant population 4 to 6 wk after Oct/Nov planting was observed for 2,4-D plus aminopyralid (6.3) and 2,4-D plus picloram (7.3). Only 2,4-D plus aminopyralid resulted in yield reduction from the nontreated (29.8%). Field experiments also evaluated simulated residual effects of fluroxypyr plus triclopyr and 2, 4-D plus picloram on ball (Trifolium nigrescens viv.), white (Trifolium repens L.), crimson (Trifolium incarnatum L.) and red (Trifolium pretense L.) clover. For all clovers, when averaged across herbicide rates, plant population 214/217 and ground cover 86/87 DAP was equivalent for fluroxypyr plus triclopyr and the non-treated and greater than 2,4-D plus picloram. Averaged across herbicide rates, clover height was equivalent for fluroxypyr plus triclopyr and the non-treated. 2,4-D plus picloram reduced clover height 67 to 88% from the non-treated. Ground cover 161/196 DAP, when averaged across clovers, for all rates of fluroxypyr plus triclopyr was equivalent to the non-treated. All rates of 2,4-D plus picloram were reduced compared to the non-treated (1.4 to 4.0 vs 7.9). Averaged across clovers, plant height following all rates of fluroxypyr plus triclopyr was equivalent to the non-treated (14.2 to 14.3 vs 15.3 cm) and greater than 2,4-D plus picloram. Compared with the non-treated, 2,4-D plus picloram at 25, 38, and 50% x rates reduced height 58, 76, and 85% respectively. Averaged across clover species, yield for fluroxypyr plus triclopyr at all rates was equivalent to the non-treated (2624.0 to 2839.7 vs 2811.9 kg/ha). Compared with the non-treated, 2,4-D plus picloram at 25, 38, and 50% x rate reduced yield 65,89, and 99%, respectively.

Burgeoning demand for sweetpotato [Ipomoea batatas (L.) Lam] is being driven by strong consumer consumption of fries and robust fresh market sales. Acreage has rebounded to meet needs, but increased supply has weighed negatively on fresh market prices, and processing sweetpotato is generally at a low price point. Growers are challenged with increasing production costs and labor is the most expensive input; reducing labor costs through mechanized harvest is critical. Many popular varieties of sweetpotato are highly susceptible to skinning damage and the problems that are associated with exposed root flesh such as rotting, weight loss, and sunken areas. The present study compared methods to assess skinning damage and determine if it is possible to breed for a more skinning resistant variety to aid in further mechanization. A torque wrench was found best at quantifying the amount of force required to cause skinning damage. A two year study of a parent and offspring population using the torque wrench found a heritability estimate of 0.10 on an individual plant basis and a 0.63 heritability on a family basis. It is assumed that an estimate above 0.50 is sufficient to improve a trait and data showed utility using families in breeding scheme, albeit this brings complications. The research also examined genes differentially expressed at skinning injury sites in 2 different environments. Over expression of genes involved in healing may decrease damage that does occur after skinning damage and complement a more durable skin. Consequences of skinning are lessened by curing roots (32° C; 85% relative humidity for 5 days); wound sites are rapidly healed with nominal desiccation. Cyt P450 and Ext, genes associated with periderm formation and wound healing, were found up-regulated in a curing environment compared to skinned sites at ambient outside conditions (conditions varied from approximately 26-30°C, with 50-70% RH ) over multiple time points (2 h, 4 h, and 24 h after skinning). Multiple genes associated with stress were found up-regulated in the ambient conditions. It is hypothesized that selection of genotypes with a more durable skin and enhanced repair mechanisms may further the quest towards mechanized harvest.

"Major Subject: Molecular and Enviromental Plant Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.

"Major Subject: Molecular and Enviromental Plant Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.

"Major Subject: Molecular and Enviromental Plant Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.

"Major Subject: Molecular and Enviromental Plant Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.

"Major Subject: Molecular and Enviromental Plant Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.