Calcareous soils make up some of the most productive agriculture lands in Louisiana. Due to their minimal occurrence little research has been done on these soils. Understanding phosphorus (P) chemistry is necessary for environmentally sound management of these soils. In this study, P speciation was investigated using several chemical fractionation procedures as well as x-ray absorption near-edge spectroscopy (XANES) coupled with principal component analysis (PCA) and least-squares linear combination fitting (LCF) on five calcareous Louisiana soils of different geological origins. Phosphorus sorption isotherm parameters were determined and their relationships with other properties were evaluated. In addition, Zinc (Zn) lability due to the interaction with P and other fertilizer nutrients was characterized and a fertilizer P and Zn response trial for corn on a calcareous Norwood silt loam soil was conducted. The results showed that these calcareous soils were dominated by Ca-P phases. All chemically defined sequential P fractions except HCl-P were significantly correlated with different Fe fractions especially amorphous Fe, indicating that Fe-oxides play an important role in P retention. A significant correlation was found between P speciation by XANES analysis and sequential P fractionation for total Ca-phosphates as well as total Fe-/Al-phosphates (R² ≥ 0.81, P ≤ 0.0383). Further, an inclusion of the NaHCO₃ extraction in chemical fractionation procedures caused a redistribution of Fe-/Al-P while Ca-P was unchanged. The evaluation on P and Zn interaction showed that the presence of PO₄^3- decreased where as NH₄⁺ increased Zn lability, suggesting that Zn and P fertilizer placement should be separated while the simultaneous application of Zn and ammonium-N amendments could improve plant Zn availability. The field experiment exhibited a P fertilizer response when Bray II soil test P was < 220 mg kg^-1 while a Zn fertilizer response was dependent on P levels even when soil test Zn was very low by DTPA. It is concluded that P forms not only control P retention mechanisms for agronomic and environmental availability but also affect management of other nutrients in soils.

Studies were conducted in 2001-2004 evaluating genotype by environment interactions in cotton (Gossypium hirsutum L.). Genotype by Environment interactions were characterized using GGE Biplot for conventional cotton cultivars and their transgenic derivatives. Significant interactions existed for several non-target traits. Transgenic cultivars were taller, had greater height to node ratios, larger seed, and lower lint percentages. Transgenic cultivars containing the Bollgard gene yielded more than their conventional parents and STV4691B was the highest yielding, most stable cultivar. In 2002-2004, GGE Biplot was used to identify two levels (high/low) of discriminating locations for three distinct selection criteria. Crosses were made with parents recommended by a least squares means analysis for each population criteria and F₂ plants were planted in the high and low discriminating locations for each population. Gains by selection (h²) were calculated by regressing the F_2:3 plants on their F₂ parents. Genotypic variance was greater among F_2:3 progeny in discriminating environments compared to non-discriminating environments, regardless of population. Heritability was greater in the population containing fiber traits compared to yield. In 2004, GGE Biplot was compared to other widely-accepted stability analysis tools. Correlation coefficients between GGE biplot (stability evaluation) and the Cultivar Superiority Measure, Shukla's Stability Variance, the Eberhart-Russell regression model, Kang's yield stability statistic, and AMMI were 0.54, 0.91, 0.86, 0.63, and 0.55, respectively. Correlation coefficients between GGE biplot (mean performance + stability evaluation) and the Cultivar Superiority Measure, the Eberhart-Russell regression model, Kang's yield stability statistic, and AMMI were 0.95, 0.60, 0.85, and -0.33, respectively. Based on the results of this study and our experience using GGE Biplot, Model 3 with an entry-focused scaling is the most valuable analysis for breeders engaged in cultivar development. GGE Biplot was used with the 1993-2003 Louisiana Official Variety Trials to identify the most desirable (discriminating and representative) test locations in Louisiana for yield and fiber length. St. Joseph loam was ranked 1st for yield, Winnsboro irrigated was ranked 1st for fiber length, and St. Joseph loam was ranked 1st to simultaneously select for both traits. Winnsboro non-irrigated should not be used to select for yield or fiber length.

Runoff of sediments and nutrients, particularly phosphorus (P) from agricultural fields is considered as one of the main causes of water quality impairment. Very little research has been done on relating suspended solids in runoff to soil test information. This two-part study was aimed at:1) evaluating the relationship between total suspended solids (TSS), P forms in runoff, and soil salinity measurements, particularly electrical conductivity (EC), and 2) establishing the relationships between runoff P forms and the various soil test P measures, across a variety of selected Louisiana calcareous and acid soils. In the first part of the study, five Louisiana soils with clay content of 27 to 44% were selected, treated with different concentrations of salt solution (7.5 to 30 dS m-1), subjected to simulated rainfall, and various runoff parameters were measured. The TSS, total phosphorus (TP), and particulate phosphorus (PP) in runoff were found to decrease with consecutive simulated rainfall event. A highly significant relationship existed between TSS and turbidity of the runoff water (R2 = 0.92, P < 0.001). Each of TSS, turbidity, TP and PP negatively correlated to soil EC (R2 = 0.22-0.29, P < 0.05). A very significant relationship was observed between TP and TSS in runoff (R2 = 0.73, P < 0.001). In the second part of the study, nine soils of varying chemical and physical properties (pH, % clay, CaCO3 etc.) were used. The results revealed that among the measures of soil P examined, only water extractable P and Mehlich III P were reliable indicators of DP losses, explaining about 86% and 57% respectively, of the variability in runoff DP. The study showed that Olsen P (R2 = 0.73, P < 0.01), NH4-oxalate P (R2 = 0.50, P < 0.05), and NaOH P (R2 = 0.50, P < 0.05), reasonably correlated with runoff TP. Among the calcareous soils, Bray II P, NH4-oxalate P and NaOH P each explained about 40% of the variability associated with TP in runoff water. Along with soil test P measures, soil EC relationship with TSS could be useful in predicting P losses in runoff and hence requires further examination.

Field studies evaluated the effect of plant population and seeding configuration on cotton (Gossypium hirsutum L.) growth and yield. Seeding configuration did not influence plant growth and development parameters. Averaged across seeding configurations, plants grown at a density of 152,833 plants ha-1 were taller than plants grown at 50,958 and 33,975 plants ha-1, and produced fewer mainstem nodes than all other populations. A 4- and 5-day (2003) and 13- and 14-day (2004) delay in peak bloom was associated with populations of 50,958 and 33,975 plants ha-1, respectively, when compared to 152,833 plants ha-1. Lint yield was not significantly reduced until plant population was lowered to 33,975 (30.5 cm plant spacing) or 50,958 (three plants per hill, 60 cm hill spacing) plants ha-1. Fiber properties were not influenced by plant population or seeding configuration. In field experiments conducted at two Louisiana locations, the effect of late-season insect simulated defoliation (manual leaf removal) and premature harvest-aid application on cotton yield and fiber quality was evaluated. Results suggest a negative impact on yield and fiber quality should not occur when terminating management strategies for late-season bottom defoliating insects at plant development ≥ NAWF5 (five nodes above the uppermost first position white flower, i.e. cutout) +550 HU (heat units), while harvest-aid application should not be initiated until plant development exceeds NAWF5+750 HU. Data obtained from field studies conducted in both Louisiana and Tennessee, which evaluated the effect of carrier volume and nozzle type on cotton harvest-aid efficacy, determined that harvest-aids should be applied through flat fan or hollow cone nozzles at carrier volumes of at least 93.5 L ha-1. These applications are necessary to maximize efficacy, by increasing canopy penetration by spray droplets, to achieve adequate defoliation for a once over harvest. Defoliation timing experiments in Louisiana identified 40 to 60 percent open bolls as the stage of crop maturity when harvest-aid application will result in maximum lint yields. However, a second harvest may be necessary to realize maximum lint yield. Delaying defoliation until after 75 percent open bolls may have detrimental effects on fiber quality resulting in discounts and reduced gross revenue.

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.