The coastal wetlands play a central role in maintaining productivity of the Gulf of Mexico while protecting coastal regions during severe storms. To help offset the loss of coastal marsh, there is growing interest in the beneficial use of dredge spoil for reconstruction of eroded areas. Hydraulic dredges are routinely employed to maintain navigation and the unconsolidated sediments can be pumped considerable distances to create gently sloping wetland areas. Some areas of these reconstructed wetlands are rapidly colonized by Spartina alterniflora, the dominant vegetative species in saline areas under tidal influence. Some areas, however, fail to colonize despite favorable positions near the tidal zone. Even where volunteer colonization succeeds, marked differences in vegetative growth are commonly observed. A study was conducted to assess the impact of landscape and edaphic features on volunteer colonization along five transects (40 sites) located in a reconstructed wetland near Port Fourchon LA. Volunteer stands were observed growing 8 cm below to 45.3 cm above mean tide level (MTL). Six of the more productive sites were located at elevations above the mean high water line and the elevation of one of the most productive sites was 30.1 cm above MTL. N deficiency appears to be the primary determinant of overall productivity of S. alterniflora in this marsh, and is more acute in areas receiving lower accumulations of organic matter. The organic C and total N contents of sediments in optimal environments were 11 g C kg-1 and 0.44 g N kg-1, respectively. Concentrations of >11 g N kg-1 in either uppermost leaves or standing biomass were sufficient for optimum productivity. Highly productive plants also contained higher amounts of P and K and substantially lower amounts of Fe and Al than severely stressed plants. The failure of low-lying areas to colonize appears to be due primarily to an excessive accumulation of salts. These persistently barren areas currently or may have once served as drainage ways with insufficient flow to flush salts to open water, and therefore salts accumulated to a level where colonization is no longer possible

Correlations between spectral reflectance imagery and anthocyanin content have the potential to influence the interpretation of imagery data. The objectives of this study were to correlate leaf anthocyanin concentrations in cotton (Gossypium hirsutum L.) leaves with selected types of spectral reflectance imagery, to determine if the imagery could be used as a predictive tool for anthocyanin concentration, and to establish a baseline anthocyanin concentration in cotton leaf tissue. Field experiments were conducted in 2004 near Winnsboro, LA, with both an aerial-based camera and a hand-held device to investigate imagery responses to anthocyanin concentration. Multiple planting and sampling dates were used to produce variation in both anthocyanin concentration and imagery values. Anthocyanin concentration had a positive correlation with increasing sampling date and a negative correlation with planting date confirming that anthocyanin levels increase with crop maturity. The Normalized Difference Vegetation Index (NDVI) values recorded with a NTech GreenSeeker and the Green Normalized Difference Vegetation Index (GNDVI) values obtained from aerial imagery both had a negative and significant (p<0.01) correlation with anthocyanin concentration. NDVI values from the aerial imagery also had a negative relationship, but were not significant (p>0.05). While anthocyanin concentration in cotton leaves have an influence on spectral reflectance imagery, the effect appears to be minimal. Attempts to fit a predictive linear regression model to leaf anthocyanin concentration using spectral reflectance imagery were not successful. Laboratory experiments were also conducted using cotton seeds and cotton seedlings in a germination chamber under irradiation at approximately 100 µmol m-2 s-1 for varying lengths of time. Baseline anthocyanin content for cotton seeds was determined to be approximately 2.0E-6 mol/cm2. A significant (p<0.05) difference was observed between the mean anthocyanin concentrations of seedlings with the first true leaf exposed to 24 hours of continuous light and seeds unexposed to light. No significant (p<0.05) differences were observed in mean anthocyanin concentrations in seedlings with the first true leaf exposed to 12 hours of irradiance or less. No apparent lag period between commencement of irradiance and initiation of anthocyanin production was observed.

E. polystachya introduced at stand densities (SD) of 10,000 through 70,000 stolon segments/ha produced 5.4 to 6 stolons/introduced segment; however, 130,000 through 520,000 SD produced 1.4 to 2.1 stolons per introduced segment indicating increased intra- and inter-specific competition. Stolon production was greater than 160,000 plants/ha with 30,000 through 520,000 SD. The 520,000 SD produced a total stolon length of 318 km/ha and no difference was observed for the 260,000 SD. Total node production was 290,000 nodes/ha with an average of 29 nodes/introduced segment in the 10,000 SD and 5.4 to 9.8 nodes/introduced segment with 70,000 or greater SD indicating greater inter- and intra-specific competition. Total biomass indicated similar trends with increasing densities. In a depth of emergence study, E. polystachya shoot emergence was 31, 63, and 44% for stolons planted at the 0, 1.3, and 2.5 cm depth, respectively. Shoot emergence was 25% for 5 cm depth, which was similar to the 0 and 2.5 cm depth. In a greenhouse study, glyphosate controlled E. polystachya 91% and control was 65 to 78% for all herbicides evaluated. When treated with glyphosate, biomass production was 19% of the nontreated E. polystachya. Two studies evaluated herbicides labeled for Echinochloa crus-galli (L.) Beauv. control in rice for activity on E. polystachya. The first study included: 448 g/ha clomazone PRE, 448 g/ha clomazone plus 420 g ai/ha quinclorac delayed PRE, 448 g ai/ha pendimethalin plus 420 g/ha quinclorac DPRE, 70 g/ha imazethapyr at EPOST, and 175 g ai/ha mesotrione PRE. Each PRE herbicide was followed by 315 g/ha cyhalofop POST. The second study included: 208 g ai/ha cyhalofop EPOST fb 315 g/ha cyhalofop LPOST, 22 g ai/ha bispyribac EPOST fb 22 g/ha bispyribac LPOST, 66 g ai/ha fenoxaprop EPOST fb 86 g/ha fenoxaprop LPOST, 70 g ai/ha imazethapyr EPOST fb 70 g/ha imazethapyr LPOST and 50 g ai/ha penoxsulam MPOST. Each POST program was assessed with and without 448 g ai/ha clomazone PRE. In the first study, clomazone, imazethapyr, and pendimethalin plus quinclorac controlled E. polystachya 78 to 80%. In the second study, treatments including cyhalofop, imazethapyr, and penoxsulam controlled E. polystachya 76 to 84%.

Although registration protocol stipulates that pesticide degradation be quantified using homogeneous soil, research suggests that degradation in intact soil may give results more consistent with field data. This project examined degradation of the turf and cereal fungicide BAS 505 [N-methyl-(E)-2-methoxyamino-2-(2-((2,5-dimethylphenoxy)methyl)phenyl) acetamide]. Yearlong and four-month-long incubation studies compared degradation rates in intact cores and homogeneous (batch) samples of Ruston fine sandy loam (fine-loamy, siliceous, thermic Typic Paleudults) soil. Recovery of BAS 505 in methanol extracts was measured 12 times over the 360 d incubation by HPLC-LSC analysis, and declined to 36 % and 57 % of the amount applied in cores and batch soils, respectively, by 360 d. But degradation in cores was faster than in batch soil only after long-term incubation. Since geostatistical surveys of soil biological, chemical and physical properties at the study site revealed spatial variability, a four month incubation using soil from different landscape positions was performed to verify field-wide consistency. Recovery was measured 5 times and after 120 d decreased to 65 % and 67 % of applied in cores and batch soils (averaged across all positions), respectively. This study found no significant difference in degradation of BAS 505, either between systems for any landscape position or among positions for intact and batch soils. In both studies and systems, degradation rate decreased over time and could be described by Nth-order kinetics but not 1st-order. Sorption BAS 505 in the Ruston soil was reversible so that sorption kinetics was likely not the cause of slowing degradation rate. Decreasing microbial activity with time (as by lack of nutrient inputs) may have occurred but this was not shown by the highly variable microbial biomass C data. A follow-up greenhouse study that compared BAS 505 degradation in packed cores of Ruston soil under bermudagrass (Cynodon dactylon (L.) Pers.), bare and bare but shaded found evidence that the presence of living grass led to faster degradation of BAS 505 versus bare soil. Thus, long-term static laboratory incubations may be a poor basis for projecting environmental fate and persistence.

Field trials conducted over two years evaluated weed control programs in second generation glyphosate-resistant (GR) cotton (Gossypium hirsutum L.). In a co-application study, glyphosate applied alone at the standard rate or in combination with acephate, acetamiprid, bifenthrin, cyfluthrin, cypermethrin, dicrotophos, dimethoate, emanectin benzoate, imidacloprid, indoxacarb, lambda-cyhalothrin, methoxyfenozide, spinosad, thiamethoxam, zeta-cypermethrin, mepiquat pentaborate, sodium calcium borate, and a foliar nitrogen fertilizer resulted in similar control of barnyardgrass [Echinochloa crus-galli (L.) Beauv.] (96-97%), johnsongrass [Sorghum halepense (L.) Pers.] (98%), hemp sesbania [Sesbania herbacea (P. Mill.) McVaugh] (66-73%), pitted morningglory (Ipomoea lacunosa L.) (67-72%), and sicklepod [Senna obtusifolia (L.) H. S. Irwin & Barneby] (86-91%), regardless of application timings at 3 to 4 lf or 7 to 8 lf weed stages. Additionally, fresh weight reduction was equivalent for treatments of glyphosate alone and co-applications and ranged from 89 to 100%. Weed control data from field studies in second generation GR cotton indicate the inclusion of fluometuron preemergence (PRE) to glyphosate postemergence over-the-top (POT) programs beneficial for some, but not all species evaluated, and very little difference was observed between two or three POT applications of glyphosate. Use of fluometuron PRE can prove beneficial in maximizing yield when early season glyphosate applications are delayed. In a related study, data suggests herbicides s-metolachlor, pyrithiobac, and trifloxysulfuron provide similar season-long control of most weeds evaluated. Barnyardgrass and browntop millet [Urochloa ramosa (L.) Nguyen] control can be maximized with co-application of s-metolachlor and glyphosate. Timing of residual herbicide applied at 2, 6, or 10 lf had little or no affect on control observed. For palmer amaranth (Amaranthus palmeri S. Wats.), sicklepod, barnyardgrass, and browntop millet, season-long control was optimized with residual herbicide applied at the 2 or 10 lf growth stages. Similar yield response can be expected among herbicides evaluated in combination with glyphosate. Analysis of yield data suggest the most consistent residual herbicide application timing for optimizing yield occurred at the 2 lf growth stage.

In field research conducted over two years, red morningglory control 35 days after treatment (DAT) was at least 90 % with atrazine at 3.36 kg ai/ha, diuron plus hexazinone at 1.57 + 0.44 kg ai/ha, flumioxazin at 0.14 kg ai/ha, sulfentrazone at 0.21 kg ai/ha, and metribuzin at 2.52 kg ai/ha. At 49 DAT, atrazine at 4.48 kg/ha provided only 70 % control, which was equivalent to that for diuron plus hexazinone and flumioxazin. Sulfentrazone at 0.21 kg/ha controlled red morningglory at least 93 % 49 DAT and by 77 DAT control was 78 %. From June through October, red morningglory seedling emergence was compared for no tillage and tillage treatments. Seedling emergence was equal for the tillage treatments in July, but more seedlings emerged in August and September where plots were tilled. Total seedling emergence for the growing season was 129 plants/m² for the no tillage treatment and 195 plants/m² where plots were tilled. Seed population in soil from June through October for the treatments decreased an average of 34.7%. When grown under 30 and 50 % shade, red morningglory seedling emergence decreased around 8% compared with full sun. Increasing shade to 70 and 90 % decreased seedling emergence around 40 %. Shade did not affect red morningglory height, but biomass per plant under 90 % shade decreased 48 %. Red morningglory produced more leaf area per plant under a shade environment. In the sugarcane (Saccharum spp. hybrids) and weed competition study, red morningglory infestation in November, based on the degree of wrapping of sugarcane stalks, was 24 % when plots were maintained weed free until late June and allowed to re-infest thereafter, but was no more than 9% when weeds were allowed to re-infest in July and August. In November, re-infestation was around 8% where plots were weedy until June or July and red morningglory was removed at that point, but weeds were not present in November for the August removal treatments. For the various weed removal treatments, sugarcane and sugar yield were equivalent to the season long weed free control, but yields were reduced around 27 % when red morningglory competed with sugarcane season long.

Field research evaluated response of USG 3209 wheat to glyphosate drift representing 12.5, 6.3, and 1.6% of the usage rate of 1,120 g ai/ha (140, 70, and 18 g/ha, respectively). Applications in 140 L/ha spray volume were made at first node in late February/late March, boot stage in late March/early April, and early flowering in early to mid-April. Bleaching of leaf foliage was observed for all glyphosate rates regardless of application timing. Height 28 days after treatment (DAT) was reduced 47% with glyphosate applied at 140 g/ha at first node and around 26% for 70 g/ha applied at first node or 140 g/ha applied at boot stage. Yield was reduced 72% when glyphosate was applied at 140 g/ha at first node, 45% when applied at boot stage, and 54% when applied at flowering. For 70 g/ha wheat yield was reduced 25 to 30% for the three application timings, but yield was not reduced for 18 g/ha. In another study, response of six wheat varieties to glyphosate was the same as that observed for USG 3209. The influence of carrier volume was evaluated where glyphosate at drift rates representing 12.5 and 6.3% of 1,120 g/ha was applied to USG 3209 wheat at first node in late February/late March and at heading in early to mid April. Glyphosate was applied in constant carrier volume of 234 L/ha where herbicide concentration declined with reduction in dosage and in carrier volumes adjusted proportionally to glyphosate rate to include 30 L/ha for 12.5% rate and 15 L/ha for 6.3% rate. Glyphosate applied at first node in proportional carrier volume reduced height 42% 28 DAT, 2.8 times the reduction for glyphosate applied in 234 L/ha. Height reduction was no more than 15% when glyphosate was applied at heading regardless of carrier volume. Yield was reduced 42% when glyphosate at 140 g/ha was applied in 234 L/ha, but was reduced 54% when applied in proportional carrier volume. For 70 g/ha glyphosate applied in 234 L/ha yield was reduced 11%, but yield reduction was almost 4 times greater when applied in proportional carrier volume.

Phosphorus (P) loading into surface water from runoff and subsurface flow leaving soils subjected to long-term applications of poultry litter (PL) will degrade water quality. A practical way to reduce such loading is to remove soil P through plant uptake and harvest removal. The primary field study presented here examined the effectiveness of hay harvest utilizing a double-cropped system - perennial warm-season forage grass, common bermudagrass (CB; Cynodon dactylon (L.) Pers.), overseeded with annual ryegrass (ARG; Lolium multiflorum Lam.), a cool-season forage, in reducing soil P from a Ruston fine-sandy loam impacted by PL amendments. A secondary field study similarly examined CB, bahiagrass (BG; (Paspalum notatum Flugge.), crabgrass (CG; Digitaria sanguinalis (L.) Scop.) and switchgrass (SG; Panicum virgatum L.). The primary study was conducted as a randomized block design with three replicate plots of four previous rates of PL (0, 5, 10 and 20 Mg ha-1) applied annually (1996-2001) to CB sod, at the Calhoun Research Station in Calhoun, Louisiana. Following the last PL application, plots were overseeded with ARG in Fall 2001, forage harvested and analyzed for dry matter yield, tissue P concentration and P removal. Double-cropped ARG and CB were harvested as hay and analyzed as above through 2005, giving four years of data. In Spring 2002, four small sub-plots BG, CB, CG and SG were established in the upper end of the main plots used in the primary study and corresponding data for these warm-season forages was collected for three years. Over four years, ARG removed more soil P than did CB (112 vs. 76 kg P ha-1, averaged across all rates of previous PL application and soil Bray2 P levels) because of higher tissue P concentration. The double-cropped hay system, therefore, removed nearly 200 kg P ha-1 or reduced soil P by about 100 mg kg-1. Despite low tissue P concentration, high biomass production by SG extracted an average of 64 kg P ha-1 annually over three years. This rate was significantly greater than that for CB, BG or CB, and perhaps equaled or exceeded the combined rate for ARG and CB in the double-cropped system.

ABSTRACT Sugarcane suckers, otherwise known as bullshoots or water sprouts have been reported in south Louisiana. Suckers are physiologically immature shoots and tend to accumulate less sucrose compared to mature stalks. Suckers may affect productivity by increasing biomass while contributing little to sucrose content. An understanding of the environmental and cultural factors responsible for sugarcane sucker production in Louisiana may provide answers that could be useful in minimizing its negative effect on production. The study objective was to investigate the effects of nitrogen (N) treatments on sugarcane and sugarcane sucker production in variety HoCP 85-845 under Louisiana growing conditions. This variety had previously been identified as having a high propensity to produce suckers. A secondary objective was to investigate the effects of a split N application on sugarcane sucker production and sugar yield. Two experiments were conducted; the first was planted in the fall of 2000 (plant cane data) on a Sharky clay soil and a second was planted in the fall of 2001 (ratoon and plant cane data) on a Commerce silt loam soil. Significant differences (P ¡Ü 0.05) in sucker population were found among treatments in the 2001 ratoon crop in mid-September before Tropical Storm Isidore and Hurricane Lili affected southern Louisiana. Severe lodging due to the two tropical systems prevented stalk counts from being made in the 2001 plantcane experiment. At time of harvest (mid-December) significant differences were found for cane yield, sucrose content, and stalk weight in both experiments however no significant differences were found among treatments for sucker population. These results were not conclusive because of the high amounts of rainfall and severe lodging experienced. On average, suckers contributed 1.6% and 0.93% to total cane yield in the 2001 ratoon and plantcane crops, respectively. For sugar yield in the same year and crops, 9.4% and 2.2% of total sugar yield was attributed to suckers, respectively. Given the added costs of transportation and milling, suckers are likely to have an overall negative effect on sugar production and processing.

The goal of this study is to evaluate the potential of three plants, Thelypteris palustris (marsh fern), Asparagus sprengeri (asparagus fern), and Lolium perenne (perennial ryegrass) for use in phytoremediation of arsenic-contaminated soils. Specifically, the objectives of this study are to (1) confirm if arsenic accumulation occurs in the selected plants, (2) to examine morphological effects of arsenic in the selected plants, and (3) to evaluate the oxidation state of arsenic upon accumulation in the selected plants. The analytical method combination of ICP-MS, SEM, and XANES was used to accomplish the objectives of this study. The results indicate marsh fern, asparagus fern, and perennial ryegrass all uptake arsenic. Bioaccumulation factors of all plants except ryegrass are > 1, indicating that they are accumulators of arsenic. The bioaccumulation factors of marsh fern were found to be in the range of the bioaccumulation factors (>10) of the known hyperaccumulator, Pteris vittata. After arsenic exposure, plants exhibited necrosis or vascular system degradation and collapse. All plants contained a mixture of the arsenic oxidation states of As (V), As (III), and/or As (0). Ryegrass was the only plant to contain As (III) chemically associated with sulfur. As (V) and/or As (0) were the dominant oxidation states in above-ground biomass of asparagus fern and ryegrass. As (V) was the dominant oxidation state in the roots of marsh fern. In conclusion, marsh fern, asparagus fern, and ryegrass have the ability to survive arsenic exposure and accumulate arsenic into above-ground parts. Marsh fern is a good candidate for phytoextraction of areas contaminated with low levels of arsenic. Although, asparagus fern and ryegrass are not good candidates for phytoextraction, their potential in phytostabilization should be further investigated.