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Annual application of N at rates of 118 (118N), 236 (236N), and 354 (354N) kg•ha⁻¹ on 35 year old 'Western Schley' pecan trees during four years had little effect on mineral composition and foliar N. No differences in yield, nut quality, and reproductive characteristics were found. Alternate bearing intensity in four consecutive years was 37, 33 and 28% in 118N, 236N, and 354N, respectively, with a significant linear response. Rates from 118 to 236 kg N•ha⁻¹ satisfy N needs for pecan in irrigated pecan orchard of the southwest of United States. The effect of one-time banding of zinc sulfate (74 kg Zn•ha⁻¹) and zinc-EDTA (19 kg Zn•ha⁻¹) was evaluated over a period of four years on ‘Wichita’ pecans growing in alkaline soil. Significant differences in foliar Zn levels were found one month after application of Zinc-EDTA. Differences also were noted during the next three years on approximately 25% of the sampling dates. Yield, leaflet area, and trunk cross sectional area were not affected. Zinc-EDTA increased Zn uptake by 'Wichita' pecan trees in alkaline conditions during three years. A field study indicated that manure or manure plus Zn increased foliar Zn levels in pecans after two years of annual applications. Manure (24 ton ha⁻¹) plus zinc sulfate (258 kg Zn•ha⁻¹ as zinc sulfate) treatment had the highest foliar Zn levels. No differences were observed in trunk growth, leaf area, leaf weight, nut filling, and yield. Manganese toxicity symptoms are exhibited when leaf Mn levels are higher than 1700 μg•g⁻¹ during the standard date sampling of July and affected reproductive characteristics and leaf and shoot growth. More severe visible symptoms include delayed budbreak and die-back of young shoots. In potted pecan trees, zinc EDTA treated trees had a foliar Zn of 244 μg•g⁻¹, in foliar sprayed trees (eight foliar sprays of a combination of zinc sulfate and UAN32) had 140 μg•g⁻¹, and in control trees had 33 μg•g⁻¹. Soil adsorption isotherms showed that of the three fertilizers evaluated Zn sulfate was adsorbed most strongly by the soil (1.5 mg Zn•g⁻¹ of soil). Soil adsorption from Zn EDTA solutions was insignificant.

Weed control is typically achieved by broadcast spraying postemergence herbicides on the entire orchard floor which wastes chemical by spraying bare ground. Growers can account for spatial variation in weed density and only spray weedy areas instead of applying herbicide to entire fields by using the automatic spot-sprayer, WeedSeeker sprayer. We conducted field experiments in flood- and microsprinikler-irrigated lemon orchards, and flood- and sprinkler-irrigated pecan orchards to measure the amount of herbicide applied, weed control, tree yield, and the economic value of adopting the WeedSeeker sprayer compared to conventional boom spray technology. The WeedSeeker sprayer reduced cumulative herbicide use by at least 36% compared to the conventional boom sprayer at all sites. Weed control obtained using the WeedSeeker sprayer was usually similar to the conventional boom sprayer. There were no effects of the treatments on yield at any location. The partial budget analysis, used to determine the economic value of adopting the technology, showed that as the area of the orchard and the cost of the herbicide increased, the time to recover the initial investment in the WeedSeeker sprayer decreased. The investment in the technology can typically be recovered in less than five years in Arizona lemon and pecan orchards.We also conducted greenhouse experiments to determine the effect of various sensitivity settings and leaf area on the operational efficiency of the WeedSeeker sprayer. The WeedSeeker sprayer did not detect and spray all broadleaf and monocot plants unless a sensitive setting was used. The WeedSeeker sprayer was more efficient when detecting broadleaf plants compared to monocot plants. Our results indicate that operating the WeedSeeker sprayer using a sensitive setting (sensitivity level 2) will result in the most efficient detection of weeds.Finally, field studies were conducted in a non-bearing pecan orchard to evaluate weed management systems using various postemergence and preemergence herbicides. Most postemergence herbicides controlled the weed species present in the orchard. Tank mixing the herbicides generally resulted in greater control compared to applying them alone. All preemergence herbicides reduced the weed emergence compared to not using a preemergence herbicide. No pecan tree damage was observed in any treatment.

Thesis (M.S.)--Texas State University-San Marcos, 2008. / Vita. Appendices: leaves 34-54. Includes bibliographical references (leaves 31-33). Also available on microfilm.

Master of Science / Food Science Institute - Human Nutrition / Kadri Koppel / Pecan [Carya illinoinensis(Wangenh.) K. Koch] is a native North American nut tree that has progressed into a significant agricultural crop. Flavor characteristics were evaluated for sixteen pecan cultivars: ‘Giles’, ‘Hirschi’, ‘Maramec’, ‘Oswego’, ‘Lakota’, ‘Chetopa’, ‘Colby’, ‘Witte’, ‘Dooley’, ‘Kanza’, ‘Pawnee’, ‘Stuart’, ‘Chickasaw’, ‘Peruque’, ‘Major’, and ‘Henning’ using descriptive sensory analysis. A trained panel consisting of six panelists first developed a vocabulary for the raw pecans and scored the intensities of the samples for 20 flavor attributes. Results showed that the sixteen samples differed significantly (P ≤ 0.05) on 10 of the attributes. ‘Giles’, ‘Lakota’, and ‘Pawnee’ differed from the other 13 cultivars for the majority of the attributes. The remaining thirteen cultivars showed few differences in individual attribute ratings, but did show differences when mapped using multivariate techniques indicating as many as two clusters of pecan cultivars based on flavor. The same sixteen cultivars were then roasted and evaluated using descriptive sensory analysis by the same trained panel using the same 20 flavor attributes. Three texture attributes were also evaluated. These results were compared to the results from the raw pecans. Results showed that 4 attributes differed significantly across all cultivars when raw and roasted flavor was compared. Ten of the flavor attributes had higher intensities for the roasted pecans than for the raw pecans. Most of these attributes fell within the categories of ‘nutty’ and ‘sweet’. When pecans were roasted many flavor attributes were intensified, as compared to when they were raw. How the flavor of the sixteen cultivars changed over a 12 month period was then evaluated. Raw pecans were evaluated when fresh, at 3 months, 6 months, 9 months, and 12 months by descriptive sensory analysis. A trained six member panel evaluated four flavor attributes at all five time points. Results showed that bitter had the highest intensity scores for all 16 cultivars at all 5 time points. Rancidity increased over time and sweetness decreased over time for all attributes. The results from these studies can be used as a baseline for future pecan research.

This study evaluates the effects of nitrogen and phosphorus response in young (two- and three-year-old), non-bearing,'Western Schley' and 'Wichita' varieties of pecan (Carya illinoinensis (Wangenh.) C. Koch) grown in two orchards in San Simon, AZ. Using tree trunk diameter and rates of photosynthesis, transpiration, stomatal conductance, and transpiration as proxies for tree growth and positive response, and by analyzing foliar elemental concentrations of N and P, preliminary results suggest that 'Wichita' responds better than 'Western' to N and P fertilizer with respect to tree growth. Additions of nitrogen ranging from 5.6 kg N·ha⁻¹ to 35.9 kg N·ha⁻¹ increased foliar N concentration in 'Wichita', although there was no response to photosynthesis, stomatal conductance, intracellular CO₂, or transpiration. Additions of phosphorus fertilizer up to 112 kg·ha⁻¹ improved tree growth; and growth increased with increasing foliar P concentration.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This study evaluated the effects of a major chlorine disturbance on fish communities in Pecan creek by the City of Denton's Pecan Creek Water Reclamation Plant. Fish communities in Pecan Creek were sampled using a depletion methodology during February, April, July, and November, 1999. February and April sampling events showed that the fish communities were severely impacted by the chlorine. Sampling during July and November showed fish communities recovered in Pecan Creek. The first-twenty minutes of shocking and seining data were analyzed to mirror an equal effort methodology. This methodology was compared to the depletion methodology to see if the equal effort methodology could adequately monitor the recovery of Pecan Creek after the chlorine disturbance. It was determined that the equal effort methodology was capable of monitoring the recovery of Pecan Creek, but could not accurately represent the fisheries community as well as the depletion method. These data using the twenty-minute study were compared to a previous study. Results of this study were similar to those found in a previous study, although fish communities were more severely impacted and took longer to recover.

Pecan Creek flows southeast through the City of Denton, Texas. Characterized as an urban watershed, the basin covers approximately 63.5 km2. Pecan Creek is an intermittent stream that receives nonpoint runoff from urban landuses, and the City of Denton's wastewater treatment plant, Pecan Creek Water Reclamation Plant, discharges effluent to the stream. Downstream from the City of Denton and the wastewater treatment plant, Pecan Creek flows about 6,000 m through agricultural, pasture, and forested landscapes into Copas Cove of Lake Lewisville, creating backwater conditions. Pecan Creek water quality and chemistry were monitored from August 1997 to October 2001. Water quality was influenced by seasonal, spatial, climatic, and diurnal dynamics. Wastewater effluent discharged from the Pecan Creek Water Reclamation Plant had the greatest influence on water quality of the stream and backwaters. Water quality monitoring of Pecan Creek demonstrated that dissolved oxygen standards for the protection of aquatic life were being achieved. Water quality modeling of Pecan Creek was completed to assess future increases in effluent flow from the Pecan Creek Water Reclamation Plant. Water quality modeling indicated that dissolved oxygen standards would not be achieved at the future effluent flow of 21 MGD and at NPDES permitted loadings. Model results with application of a safety factor indicated that the maximum allowable concentrations for a 21 MGD discharge would be 2.3 mg/L of ammonia and 7.0 mg/L of biochemical oxygen demand at summer conditions. Drought conditions that occurred from 1998 to 2001 reduced water levels in Lake Lewisville and impacted dissolved oxygen water quality in Pecan Creek. Water quality observations made during the period of drought allowed for the development of a model to estimate the zone of the dissolved oxygen sag in Pecan Creek based on reservoir elevation. Finally, monitoring results were analyzed with nonparametric statistical procedures to detect water quality changes in the backwater area of Pecan Creek, as influenced by storm events.