Research is needed to ensure proper cotton N fertilization in various production practices without the detrimental effects of excess fertilization on yield and the environment. The objectives were i) to evaluate the effect of residual N on the uptake efficiency of cotton-applied N when following corn in rotation, ii) evaluate the potential for using leaf blade analysis and preset N thresholds to trigger foliar applications of N to cotton grown on clay soils and iii) evaluate the effect of preplant N on early root and shoot growth and N assimilation of cotton grown on a clay soil. Nitrogen rates of 0, 56 and 112 kg N ha^-1 as double labeled 5 atom% ¹⁵N NH₄NO₃^- were applied to cotton grown on Commerce silt loam (fine-silty, mixed, nonacid, thermic Aeric Fluvaquent) following previous corn N rates of 0, 168 and 280 kg N ha^-1. Total dry matter accumulation, total N assimilation and seedcotton yield on the upper third of the plant increased as corn- and cotton-applied N increased. Recovery of labeled N ranged from 40-53% in 1999 and 30-58% in 2000 and was highest following 0 or 168 kg N ha^-1 previous corn-applied N in both years. More plant N assimilation was soil-derived in both years following 280 kg corn-applied N ha^-1. Application of 112 kg N ha^-1 resulted in the most ¹⁵N assimilated but uptake efficiency was the lowest. Seedcotton yields of cotton grown on Sharkey clay (very fine, montmorillonitic, non-acid, thermic, Vertic Haplaquepts) using 44 or 67 kg soil-applied N ha^-1 along with foliar N as needed averaged 622 kg ha^-1 less than the recommended soil-applied rate of 134 kg N ha^-1 although N use efficiency was 34% higher. The lower yield occurred because of fewer bolls on the second and third fruiting positions of upper sympodial branches. Preplant N rate increased dry matter partitioning to shoots with potentially larger N reserves. This provided ample vegetative growth, more branching and production of fruiting sites, and provided adequate assimilate to meet this increased demand. Increased cotton yield appeared to be the result of N accumulation and not greater root growth.

Adsorption-desorption and transport behavior of pesticides are important processes that influence the amount retained by the soil and that which is susceptible to runoff or movement within the soil profile. Kinetic batch experiments were used to study the adsorption-desorption behavior of metolachlor (a non-ionic herbicide) and deltamethrin (a pyrethroid insectcide) in soils, and atrazine (a triazine) in sugarcane mulch residue. Miscible displacement experiments under steady flow conditions were carried out to examine the mobility of these pesticides in soils. Metolachlor adsorption and desorption by Sharkey clay soil(Very-fine, smectitic, thermic Chromic Epiaquerts) and Commerce silty loam soil (Fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Epiaquepts) soil were strongly kinetic. The Kd values of metolachlor adsorption for Sharkey were significantly higher than for Commerce. After six desorption steps, the average metolachlor desorbed was 30.5% and 43.9% for Sharkey and Commerce, respectively, and was dependent on the initial input concentration. Adsorption and desorption of atrazine by sugarcane mulch exhibited extensive kinetic behavior. Adsorption isotherms appeared linear for all reaction times. A linear multireaction model which accounted for reversible equilibrium and kinetic retention along with a consecutive irreversible reaction described both adsorption and desorption of atrazine retention results (r2=0.99). Deltamethrin retention by soils was strong, and positively related with cation-exchange capacity (CEC) and negatively related with soil pH. Deltamethrin recovery was dependent upon the initial input concentration, and did not exceed 10.2% of the total amount adsorbed for all the four soils (Sharkey clay, Mahan sand loam, Vacherie silty loam and Mhoon silt clay loam) representing a wide range of organic matter and clay contents. Extremely low mobility and thus strong retention for deltamethrin in the soil columns were observed. A new hysteresis coefficient based upon the difference in the area between adsorption and desorption isotherms was proposed. This coefficient was capable of quantifying hysteresis for both types of desorption isotherms: traditional desorption isotherms and time-dependent desorption isotherms. Results suggested that when an isotherm is measured based upon laboratory adsorption-desorption experiments or field measurements, equal reaction times should be maintained.

Smooth cordgrass (S. alterniflora) is a perennial grass that dominates the salt marsh in tidal wetlands along the Atlantic and Gulf Coast of North America and has been used for preventing soil erosion and restoring wetlands. Accessions collected from south Louisiana were studied to investigate flowering phenology, pollen viability, crossability, and seed production. S. alterniflora exhibited protogynous flowering where stigmas exserted 2 to 5 days from the floret prior to anthesis. Pollen shed primarily between 8:00 and 10:00 AM. Pollens were viable with average germination of 69% and stigma was receptive after exsertion. Pollen germinated in 15 minutes and pollen tubes reached micropyle in 55 to 75 minutes after contacting stigma. Protogyny could be used to produce controlled hybrid without emasculation and it could reduce tedious labor required for making crosses. S. alterniflora was cross-pollinated with 52% seed set for cross-pollination and 26% for self-pollination. Flowering started in early July and ended by the middle of October with a flowering peak between early September and early October. During the flowering peak, seed set, kernel weight, and seed viability were positively correlated to flowering date while unfilled and total seeds/panicle were negatively correlated with flowering date. Kernel weight, flowering date, seed weight/panicle, and panicle height were positively correlated with seed set. Plant flowering during the peak period might produce better seed set and seed weight. Field investigation showed an average seed set of 47% with range from 0 to 94% for S. alterniflora, which provided large opportunity for selection. Several lines with improved characteristics were selected and would be valuable for recurrent selection program with an objective of developing improved S. alterniflora populations. However, short term breeding objective should be focused on selection of plants from native collection that have high percentage of seed set, germination, and broad adaptability.

Uniola paniculata (sea oats) has been used extensively to build artificial dunes as well as stabilize existing dunes along the southern Atlantic and Gulf of Mexico coasts of United States. A breeding program could enhance coastal restoration by developing improved plants for beach restoration. Our goal was to initiate a successful breeding program for sea oats adapted to low dune profiles, with high seed yield and germination, and superior vegetative biomass essential for reducing coastal erosion. The specific objectives were to: 1) examine effect of storage environment on sea oats seed germination; 2) determine time necessary for sea oats seeds to germinate; 3) determine sea oats seed moisture content; 4) determine pathogen incidence during germination; 5) determine survival and performance of vegetative sea oats plants and sea oats seedlings at beach environments with shallow dune profiles; 6) develop efficient methods to identify saturation tolerant sea oats lines; 7) determine sea oats seed yield in natural and artificial environments and 8) identify fungal and bacterial pathogens of sea oats seed. Sea oats seed stored in hermetically sealed jars at room temperature had highest average germination and seed germination was highest 21 days after germination. Sea oats seed moisture content, ranged from 6 to 16 %, and was negatively correlated with germination. Small sea oats seedlings had highest mortality however, seedling cost significantly less than vegetative plants. Increasing seedling densities could reduce production costs and result in acceptable survival rates accompanied with genetic diversity. We found that small seedlings flooded continuously to 14 cm depth in greenhouse for 3 months could predict sea oats survival in saturated beach conditions after 6 months. In 2007, 2009, 2010, and 2011 we determined sea oats seed yield in natural and artificial environments. Consistent seed yields were not obtained for either environment; however, sea oats seed were produced in artificial production nurseries. Finally, to determine seed pathogens colonizing sea oats seed, bacteria and fungi were isolated from sea oats seed harvested in 2011 and identified using both morphological and molecular techniques. The dominant bacterial genera colonizing sea oats seed were Bacillus and Enterobacter; while the dominant fungal genera were Fusarium and Curvularia.

Nitrogen (N) is one of the most important and limiting nutrients in crop production. The best management practices for N fertilization is always challenging due to its dynamic system in the nature. Remote sensing has emerged as one of the most useful technologies in modern agriculture for non-invasive monitoring of plant N status. The objectives of this research were to 1) determine the effect of water background turbidity and depth on red and red-edge reflectance based prediction models for biomass and grain yield in rice, 2) evaluate agronomic parameters of different sugar cane varieties in response to variable levels of nitrogen supply, and 3) determine the effect of sugarcane varieties on the relationships between spectral reflectance and agronomic parameters. Rice experiments were variety (CL152 and CL261) x N trial established in Crowley, LA in 2011 and 2012. Sugarcane experiments were variety (L 99-226, L 01-283, and HoCP 96-540) x N trial established in St. Gabriel and Jeanerette, LA from 2010 through 2012. Spectral reflectance and agronomic parameters were collected each week for three consecutive weeks beginning two weeks before panicle differentiation in rice and for four consecutive weeks beginning three weeks after N fertilization in sugarcane. There was no significant effect of water background (turbid or clear) on the spectral reflectance at panicle differentiation, one week after panicle differentiation, and at 50 % heading (p <0.05). Water depth slightly influenced the reflectance at red waveband but this effect was not carried over when vegetation indices were computed. Use of red-edge based vegetation indices improved the estimation of biomass and grain yield in rice. The effect of variety on the accuracy of the yield prediction model varied depending on the transformation of reflectance within the red-edge and near infrared bands i.e., into normalized (NDVI) and simple ratio (SR) forms of vegetation indices. This result was associated with the behavior of near infrared wavebands on the geometrical structure of the plant canopy. There were no significant effects of variety on grain yield prediction models using derivative based red-edge indices. Our findings showed that red-edge based NDVI and SR are better predictors of rice grain yield than red-based NDVI and SR. Red-edge based NDVI or SR indices both have potential to predict rice grain yield and rice responsiveness to N fertilization. In sugarcane, the measured agronomic variables at early growth stage, i.e. biomass, tiller number, N content, height and FAI of three sugarcane varieties and their responses to N fertilizer were highly variable across year. The sugar yield response to N determined at harvest had stronger linear relationships with N response of biomass and N content at 4 to 5 weeks after N fertilization compared with N response of height and FAI. There were no differences in leaf spectral reflectance among varieties. In canopy level-spectral reflectance, wavebands at 450-500, 650-700, and 780-830 nm showed high correlation coefficient with agronomic parameters. The vegetation indices which have the potential for predicting biomass N uptake were red and red-edge based simple ratio and normalized difference vegetation index. Varietal effect on the models for estimating biomass and N uptake was significant only when red-based vegetation indices were used (p<0.05). Addition of plant height in the model substantially improved biomass and N uptake estimation while diminishing the effect of variety. Remote sensing technology can be a potential tool to estimate biomass and N uptake in rice and sugarcane. The delivered information from this technology is useful to improve mid-season N management.

Sustainability calls for policies that meet current societal needs without compromising the needs of future generations; thus, a dual relationship between human and natural resources is required. The main goal of the current research was to introduce up-to-date environmental techniques for sustainable natural resource utilization in semiarid and humid ecosystems in short and long term. To achieve this goal, two studies were implemented. First, sustainable land use management was evaluated in a newly reclaimed, semiarid region in the Bustan 3 area (341.27 km2), Egypt. To achieve sustainable management in this agro-ecosystem; detection of land cover change, assessment of the most sensitive areas to desertification, and evaluation of land capability for agricultural use were required. Using multi-temporal remotely-sensed data in the Bustan 3, the results indicated that this area had been drastically changed from 100% barren desert land to 79% agricultural land, due to successful land reclamation efforts in the 1990s. Although 70% of this area had a good capability for agricultural production, ¡­89% of the Bustan 3 area was critically sensitive to desertification. By applying suitable land management scenarios, the land capability for agricultural use could be increased. Second, a natural resource conservation program was examined by studying the effects of compost/mulch, as a best management practice, for soil erosion control on highway roadsides in Louisiana, USA (a humid region). Louisiana is plagued by widespread impairments to surface water quality. Total suspended solids (TSS) and associated turbidity in runoff water are considered the most problematic nonpoint source pollutant of Louisiana surface waters. At the plot scale, the effects of compost/mulch on soil and water resources were evaluated. Research results showed that the use of compost/mulch without tillage incorporation successfully conserved the topsoil on the roadsides, increased soil moisture retention, moderated soil temperature, and reduced the TSS, soil loss, runoff, and water flow rate. Tillage incorporation is not recommended since it decreased the compost/mulch effectiveness in reducing runoff and sediment losses. While the two studied areas, in semiarid and humid regions, were disparate in their characteristics, sustainable natural resource management was successfully achieved by using appropriate management practices in each case.

Smooth cordgrass (Spartina alterniflora Loisel) and sugarcane (Saccharum spp. hybrids) are both grasses that belong to the family Poaceae and have significant impact on Louisiana environment and economy. Coastal Louisiana accounts to ~80% of the national wetland loss through natural and human interventions; (re)vegetation is considered an important component of coastal restoration efforts. Smooth cordgrass, a warm season marsh grass, is used as an ecosystem engineer to stabilize and restore Louisiana coastal marshes. In this study, genetic diversity was determined among 13 elite smooth cordgrass accessions of Louisiana through 276 polymorphic markers generated by 23 SSR and 32 RAPD primers. AMOVA results showed that sufficient variation existed among smooth cordgrass accessions for further exploitation in breeding program. A few genetic markers unique to specific smooth cordgrass accession(s) were also developed. Sugarcane, the number one row crop in Louisiana, is sensitive to cold; so cold tolerance is desirable to expand its cultivation in more northern environments. Cold tolerance alleles of Saccharum spontaneum can be exploited to develop sugarcane clones tolerant to low temperatures. To this end, forty differentially expressed genes (DEGs; 29 up-regulated and 11 down-regulated) were identified in a cold-tolerant clone Ho02-144 and a cold-sensitive clone L79-1002 under cold stress, using annealing control primer system. Reverse-transcription PCR (RT-PCR) analysis of the cold-responsive DEGs revealed distinctive expression profiles in the tolerant and sensitive clone. Mining of the cold-responsive DEGs yielded 12 sequences with simple sequence repeats (SSRs), which were used to design eSSR primers. Genotyping of 48 Louisiana sugarcane clones and 16 ancestral parents with these eSSRs generated 170 polymorphic markers that could classify cultivated sugarcane clones from their ancestral S. spontaneum clones at 0.23 similarity coefficient. The cold responsive genes will be useful for breeding cold tolerant sugarcane either through genetic engineering or selection through the use of gene-based markers.

Breeding for grain quality traits and resistance to sheath blight (SB), a disease caused by Rhizoctonia solani Kuhn, are important objectives for the rice (Oryza sativa L.) industry. Grain quality traits and SB resistance play an important role in the economic prosperity of commercial rice markets. The objectives of our research were to: (1) Explore performance and stability for SB resistance among doubled-haploid (DH) lines of the SB2 mapping population using GGE biplots (2) Exploit whole genome sequences of 13 inbred lines to identify non-synonymous SNPs (nsSNPs) and candidate genes for SB resistance. Genotype-by-environment interaction for SB analysis was performed using heritability-adjusted GGE (HA-GGE) biplot. DH lines were evaluated for two years in Louisiana and Arkansas; a single mega-environment was identified consisting of the four year-location combinations. HA-GGE biplot analyses identified 11 high and stable DH lines; five susceptible DH lines were also identified with greater stability than the susceptible parent used to develop the SB2 population. Material identified in this study represents a potential source of SB resistance for cultivar development. Two filtering strategies were developed to identify nsSNPs between two groups of known resistant and susceptible lines. More than 200 genes with selected nsSNPs were assigned to 42 categories based on family/gene ontology. Individual alleles of 24 nsSNPs were evaluated by PCR whose presence/absence corresponded to known resistant/susceptible phenotypes of nine additional lines. Resistant alleles were detected in two accessions of O. nivara that suggests sources for resistance occur in additional Oryza sp. Results from this study provide a foundation for future marker-assisted breeding of rice for SB resistance.

Quantitative and qualitative evaluation of compost is necessary in order to provide consumers with basic knowledge about the products composition, and to protect public health and the environment by preventing the spread of contaminated material. Current methods for analysis of basic compost properties give accurate results but are time consuming and require numerous laboratory procedures. This study evaluated the use of visible near-infrared diffuse reflectance spectroscopy (VisNIR DRS) for organic matter (OM) determination and field portable X-ray fluorescence (PXRF) spectroscopy for determination of elemental composition of composted materials. These technologies were evaluated as alternatives to standard laboratory methods for their use in rapid in situ analysis. Thirty-six compost samples from a wide range of feedstocks were gathered and tested with VisNIR DRS and PXRF. For VisNIR DRS, the influence of sample moisture on scanning results was evaluated and the use of raw reflectance, first-derivatives, and second-derivatives of the reflectance spectra were compared. Partial least squares regression (PLS) and principal component regression (PCR) were used to build regression models of VisNIR DRS scans and lab measured OM. For PXRF, the influences of sample moisture, particle size, inter-elemental interactions, and OM on PXRF scanning results were investigated. Results from the VisNIR DRS study produced a promising r2 value of 0.82 and residual prediction deviation (RPD) value of 1.72 for the ovendried first-derivative PLS model. Results indicate that VisNIR DRS shows great promise as a technique for analysis of OM content of dried compost samples, however further investigation with a larger sample set is necessary before VisNIR DRS can replace laboratory methods. Results of PXRF for elemental analysis were most promising for dried samples and for determining the elements Ca, Cr, Cu, Fe, K, Mn, P, and Zn. Arsenic detection was found to be greatly limited due to the influence of elevated Pb concentrations in the samples. Additionally, sample moisture, particle size, and OM were found to have varying influences on PXRF scan results for different elements. Compost elemental screening and definitive quantification of certain elements via PXRF is recommended by this study.

Under Louisiana climatic conditions, production of sugarcane (Saccharum spp.) is limited to a maximum growth period of nine months. To increase sucrose concentration in the crop, ripener is applied prior to harvest. The chemical ripeners, glyphosate and trinexapac-ethyl were applied to the sugarcane cultivars HoCP 96-540, L 99-226, L 99-233, HoCP 00-950, and L 01-283 eight weeks prior to harvest. When glyphosate was applied at 210 g ae/ha, TRS for the cultivars was increased 10 to 28% compared with the nontreated. Increases in TRS with glyphosate were greatest for HoCP 96-540 and L 99-226 and least for HoCP 00-950 and L 01-283. Trinexapac-ethyl at 350 g ai/ha increased TRS for the cultivars 7 to 10% and increases were greatest for L 99-233 and least for HoCP 00-950. Sugarcane yield averaged across cultivars was reduced 9% with glyphosate and 7% for trinexapac-ethyl at 350 g/ha. An increase in sugar yield per hectare, a function of TRS and sugarcane yield, was observed only when glyphosate was applied to HoCP 96-540 (16% increase) and when trinexapac-ethyl at 300 g ai/ha was applied to L 01-283 (13% increase). In a second study where eight cultivars were harvested six weeks after glyphosate application, TRS for HoCP 96-540 was increased an average of 10% compared with the nontreated and sugarcane yield was decreased 17%; sugar yield was not affected. In another study, sugarcane yield, TRS, and sugar yield were not affected by nitrogen rates of 67, 112, and 157 kg/ha. Six weeks after application of glyphosate at 210 g/ha TRS averaged across N rates was 11% greater than the nontreated and 9% greater than when trinexapac-ethyl was applied at 350 g/ha. TRS following trinexapac-ethyl was equivalent to the nontreated. Sugarcane yield and sugar yield were not affected by ripener application. In a separate study TRS and sugar yield were not affected when glyphosate or trinexapac-ethyl was applied in 75 and 150 L/ha spray volume or when none or 0.25% v/v surfactant was added to the spray solution. Averaged across spray volume and surfactant treatments, TRS was as much as 8% greater for glyphosate compared with trinexapac-ethyl.