In some corn (Zea mays L.) producing regions of the US, soil testing is still recognized as an effective decision tool for nitrogen (N) fertilizer recommendation. This study was conducted to investigate the early-season N requirement of corn based on early-season soil nitrate level and document the seasonal changes of inorganic N distribution throughout the soil profile. A Gigger silt loam soil and a Sharkey clay soil were selected to establish the trial located in northeastern Louisiana. Treatments of varying N rates were arranged in a randomized complete block design with four replications. Nitrogen fertilizer rates of 0, 67, 134, 201, 268, 335, and 403 kg N ha-1 were applied at early-season VE-V3 leaf stage. Four split application treatments of the Louisiana N recommendation (268 kg N ha-1) were applied at early-season and midseason V7-V9 leaf stages (0-268, 67-201, 134-134, 201-67 kg N ha-1). Grain yield and yield components were determined. Soil inorganic N content was determined by 1 M KCl extraction procedure followed by continuous flow injection analysis. Gigger silt loam reached a maximum yield of 13.2 Mg ha-1 when the N rate was 134-134 kg N ha-1 and soil inorganic N content was 80 kg N ha-1. Sharkey clay achieved a maximum yield of 13.1 Mg ha-1 when 268 kg N ha-1 was applied in early-season and soil inorganic N content was less than 60 kg N ha-1. Split N applications optimized yield for the Gigger silt loam, but experience a yield reduction for the Sharkey clay. The optimum N rate for the Gigger silt loam was 134-134 kg N ha-1 treatment and 201 kg N ha-1 for the Sharkey clay soil applied only at early-season (P<0.05). Nitrogen rate had a significant effect on grain yield and 100-grain weight (P<0.01) as well as N uptake and total N grain content (P<0.05). Seasonal changes in inorganic N content occurred mostly in the 0-15 cm soil layer with decreasing variability with depth. These results show the potential for using inorganic N content to determine N application method in northeastern Louisiana corn production systems.

Nitrogen (N) is often the most yield limiting nutrient, particularly in corn (Zea mays L.) production systems. In the Mid-South, high N application rates have the potential to lead to high N loss. To minimize this loss, proper N management should focus on improving N use efficiency (NUE) while optimizing productivity. The potential to achieve both tasks can be met using enhanced efficiency N fertilizer (EENF). However, limited research has directly compared the active chemicals in EENFs for corn production in the Mid-South. A study was conducted in 2013 and 2014 at two locations in Louisiana to determine the effectiveness of EENFs on yield, grain N uptake, and NUE over varying N rates. Corn grain yield significantly increased when using EENFs compared to untreated urea (average of 1.54 Mg ha-1 Winnsboro, LA and 1.30 Mg ha-1 Saint Joseph, LA [P <0.0001]). Two stabilizers paired together (NBPT and DCD) in Super U, improved yields by nearly 3.0 Mg ha-1 when applied at the recommended N rate. The rate of N transformation was observed in greenhouse experiments, to determine the effectiveness of EENFs over multiple durations of time based on NH4+ and NO3- content in the soil system. While NH4+ concentration declined within 7 days post-application, nitrification inhibitors particularly Instinct had high NH4+ concentration and low NO3- concentration in both trials. This slower transformation minimizes the potential of N fertilizer to be lost. These results suggest crop uptake of N fertilizer would increase with higher NUE. Utilizing EENFs has the potential to increase NUE through specified conditions and time periods.

Developing improved cotton cultivars depends on how cotton cultivars perform the best when under stresses. Reniform nematode is a major plant pathogen, causing 4-6% yield loss in southern United States. A variation in reproduction and pathogenicity across reniform isolates collected from Louisiana on susceptible cotton was reported. This study was conducted to determine the response of resistant/tolerant cotton genotypes to multiple reniform isolates by inoculating 10,000 juveniles into seven days old seedlings. Across genotypes, the Evan and Avoyelles isolates had significantly higher vermiform nematodes (33,793 and 27,800/250 g soil, respectively) than other isolates. Across isolates, the number of juveniles on A2-190 and Lonren-2 (5,573 and 6,013, respectively) were significantly lower than that on other genotypes. There was a significant interaction between the genotypes and isolates suggesting that the response of genotypes to reniform isolates was different. Salt stress is a major abiotic stress, affecting cotton production in the Macon Ridge and Red River regions in Louisiana. In a preliminary study, 150 day neutral primitive cotton accessions were screened at 0, 125, 250 mM NaCl under hydroponics. A promising subset was rescreened for salt tolerance in pot culture. MT11 had the lowest reduction in plant height and dry shoot weight (32% and 47%), significantly less than FM958 (43% and 66%) across salt concentrations. MT1219 had the lowest accumulation of Na+ (1,026.37 mM) at 250 mM NaCl, and significantly lower than FM958 (2,135.39 mM). Based on reduction in plant parameters, MT11, MT1219, MT45, and MT245 performed better than other genotypes. This study also showed that both hydroponics and pot culture are effective in the screening of a large number of cotton genotypes against elevated salt concentrations. In addition to stresses, cotton breeders are interested to develop a selection index, which aids in an efficient selection of multiple fibers traits. Using the data mining techniques, all developed models agreed that fiber length and strength are the most important fiber properties in determining the spinning consistency index (SCI). This study showed that SCI can be used as alternative selection index for combining the multiple fiber traits to enhance yarn spinning.

Leaf and crown rot of Liriope is an increasing problem affecting Liriope in the nursery and landscape for the past eight years primarily in the southeastern United States. Symptoms start with water soaking of leaves at the crown area, followed by yellowing of the entire leaf starting at the base. Affected crowns rot and leaves turn brown leading to death of the plants. Phytophthora palmivora and Fusarium oxysporum were isolated and identified from Big Blue Liriope symptomatic plants taken from the nursery and landscape. The pathogens were positively identified by morphological features of the pathogens and then confirmed with polymerase chain reaction. Pathogenicity tests were performed in the greenhouse using three Liriope cultivars including Emerald Goddess and Super Blue, considered to be tolerant to this disease, and Big Blue which was considered to be more susceptible. Four inoculation treatments were used: water control, Phytophthora palmivora, Fusarium oxysporum and P. palmivora + F. oxysporum. Results from this study confirm the pathogenicity of previously identified P. palmivora and F. oxysporum microorganisms causing leaf and crown rot. P. palmivora was the primary microorganism causing leaf and crown rot on Emerald Goddess and F. oxysporum on Big Blue leading to increased disease incidence and a decrease in fresh and dry weight of leaves. Super Blue showed no significant differences in fresh and dry weight of leaves and roots, and in percentage of disease incidence between the inoculation treatments (P>0.05). A survey was conducted at 11 wholesale and 7 retail nurseries in Louisiana to confirm that leaf and crown rot was a problem in Liriope production. P. palmivora and F. oxysporum were recovered from plants exhibiting leaf and crown rot symptoms which indicated that the disease was present in all nurseries. Poor sanitation and cultural practices were found to be the primary factors leading to the development and spread of leaf and crown rot disease.

Spectral vegetation index-based models that are used to estimate yield potential are commonly developed from the relationship between early-season crop canopy reflectance readings and actual yield obtained at harvest. Plant population stand can influence cane yield potential and nutrient requirement. This study was conducted at LSU AgCenter Sugar Research Station in St. Gabriel, LA to evaluate (1) the relation between estimated early season biomass yield and the spectral vegetation indices acquired at the same time, (2) nitrogen (N) response pattern between early-season biomass production and yield at harvest, and (3) the relationship between coefficient of variation (CV) among normalized difference vegetation index (NDVI) readings and stand population of cane planted as whole stalk and billets. Treatments were applied in split plots with a randomized complete block design with four replications. Varieties (Ho 02-113, US 72-114) and N application rates (0, 56, 112, and 224 kg N ha-1) were assigned as main plots and sub-plots, respectively. Another experiment was conducted with planting schemes (whole stalks and billets) and varieties (Ho 02-113, US 72-114, Ho 06-9001, Ho 06-9002, L 01-299, and L 03-371) arranged as main and sub-plots, respectively. Biomass clippings and canopy spectral reflectance readings using Jaz® spectrometer were collected at three, four, and five weeks after N application (WAN). Results showed that early-season biomass yield and its canopy reflectance collected at the same time were correlated. Overall, the relationships between vegetation indices (VIs) and biomass were best described with quadratic model at four WAN. Reflectance from red wavelengths (670 and 690 nm) and VI computed from them consistently performed better than the reflectance from red-edge wavelengths in relating early-season biomass production. Variables collected at four and five WAN showed similar response pattern to variable N rates as with harvest. Under favorable weather, billet-planted cane produced higher initial plant population compared to whole stalk-planted cane in 2013. Negative correlation was found between CV among NDVI and plant population. Coefficient of variation among red-based vegetation indices produced better correlation with plant population than those from different wavelengths. Variety had no effect on canopy spectral reflectance.

Availability of dicamba- and 2,4-D-resistant crops will provide alternative weed management options, but the risk of off-target movement of herbicides to sensitive crops is of concern. Soybean [Glycine max (L.) Merr.] treated with diglycolamine (DGA) salt of dicamba at 4.4 g ae/ha (1/128 of the recommended use rate of 560 g/ha) at V3/V4 (two to three trifoliate) was injured 39% 14 days after treatment (DAT) and injury was 97% with 280 g/ha (1/2 of use rate). For application at R1 (first flower), injury 14 DAT was 23% at 1.1 g/ha (1/512 of use rate) and was 68% at 70 g/ha (1/8 of use rate). Soybean yield for dicamba at 4.4 g/ha was reduced 4% when applied at V3/V4 and 10% at R1; for 17.5 g/ha (1/32 of use rate), yield was reduced 16% at V3/V4 and 36% at R1. Research was also conducted to evaluate volatility of various formulations of 2,4-D applied at 1,120 and 2,240 g ae/ha; dicamba applied at 560 and 1,120 g/ha; and triclopyr applied at 1,680 and 3,360 g ae/ha. Herbicides were applied to tilled soil and potted cotton (Gossypium hirsutum L.) and tomato (Solanum lycopersicum L.) plants were placed in treated strips. Injury was visually rated using four criteria (leaf cupping/crinkling/ drooping; leaf rolling/strapping; stem epinasty; and stem swelling/cracking) and a severity scale of 0 to 5 (0= no injury and 5= severe). A weighted factor assigned to each injury criterion provided an estimate of total injury on a 0 to 100% scale. Only leaf cupping/crinkling/drooping injury was observed for cotton and total injury 14 DAT was no more than 11% for the 1x rates of the herbicides and formulations. Total injury for tomato for the 1x rates of 2,4-D isooctyl ester was 36% 14 DAT and injury was attributed primarily to stem epinasty and stem swelling/cracking. For the 2,4-D dimethylamine (DMA) and acid formulations and for the dicamba DMA, DGA, and acid formulations, total injury for tomato was equivalent and was as high as 24% for the 1x rates. Injury to tomato with triclopyr butoxyethyl ester was 2.1 times that of triclopyr acid.

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.