10 pp. / Forage sorghum yields have been should to increase with narrow row spacing of 20 inches or less. The purpose of this research is to determine the effect of narrow row spacing on forage sorghum yield and quality in Arizona. Two row spacing (20 and 40 inch) and two forage sorghum hybrids (Great Scott and Silo 700D BMR) were evaluated in a study conducted at the University of Arizona Maricopa Agricultural Center in 2015. Row spacing had no effect on forage yield, moisture, plant height, or maturity even though light interception was greater for the closer row spacing. The only feed quality parameter affected by row spacing was lactic acid which increased with row spacing. Hybrid by row spacing interactions was detected for a few feed quality parameters. Decreasing forage sorghum row spacing from 40 to 20 inches does not appear to have an advantage based on the results of this study.

Comprehensive and accurate diagnosis and treatment planning is crucial in successful orthodontics. An essential part of the diagnostic exercise is to determine whether there is a tooth size/arch length discrepancy (Bishara, 2001). The mixed dentition space analysis is one method of determining this (Moyers, 1973). The procedure requires the measurement of the anteroposterior dimension of the crowns of erupted teeth and the prediction of the size of the crowns of the unerupted permanent canine and premolar teeth. The comparison of tooth sizes enables the calculation of the ‘leeway space’, which may provide for the transition to the full intercuspation of the first permanent first molars as well as the relief of a certain amount of crowding in the arch (Gianelly, 1995). To date, the application of data of methods of measuring and estimating tooth size have been limited by the relative complexities of the method (Paredes et al, 2006), and the application of the data has been limited by the demographic profile of the patient (Schirmer and Wiltshire, 1997; Khan, 2006). The aim of this study is to develop a technique of precisely measuring the mesiodistal tooth size of the crowns of teeth from computerized images of panoramic x-rays, using the Leica QWin© System of Image Analysis (Leica, UK(Pty) Ltd). Ideally, this method would be accurate, reproducible and easy to use by a clinician. Thirty sets of study casts and the corresponding panoramic radiographs of patients in the mixed dentition stage of dental development were chosen, according to specific criteria, from the archived records of the Undergraduate Clinic at The School of Oral Health Sciences, University of the Witwatersrand. On the study casts, the mesio-distal widths of the second deciduous molar (‘e’) and of the first permanent molar (‘6’) teeth in each quadrant were measured with a digital vernier caliper. The corresponding radiographs were digitally photographed at a fixed distance, and uploaded onto the computer programme. A magnification factor was determined using the image of a premeasured object. The images of the ‘e’ and the ‘6’, together with the image of the unerupted second premolar tooth (‘5’) were measured with the calibrated linear function of the Leica QWin© System. The data was thus corrected for by the relevant magnification factor. The size differential between the ‘e’ and the ‘5’, representative of the leeway space, was then calculated. A calculation of the intra-examiner repeatability demonstrated a low co-efficient of variation of the measurements recorded on both the study casts and on the computer. The measurements of the teeth taken on the study casts were compared with the corrected measurements of the same teeth taken from the computer images of the teeth. Tooth size measurements taken with the Leica QWin System were greater than those taken with the vernier calipers. In both methods the sizes of the teeth were larger in the mandible than in the maxilla. This observation was also reported by Kraus et al (1969). The values for leeway space were calculated in both jaws. The mean values of leeway space in the maxilla were 0.81mm on the left hand side and 1.08mm on the right hand side, and 2.43mm on the left hand side and 2.59mm on the right hand side in the mandible. These values were similar to those recorded by Nance (1947) and by Bishara et al (1988) who also found that values of leeway space were smaller in the maxilla than in the mandible. The accuracy of the measurements taken with the proposed method was found to be dependent upon correct patient positioning in the focal trough of the machine at the time of panoramic radiographic exposure, the use of a marker known in size placed at the site to be measured in order to correct measurements for magnification and the definition of corresponding mesio-distal points on the teeth from which measurements would be taken on both sets of records.

There is renewed interest in cotton performance grown using various row spacings and plantings patterns in the Midsouth. Cotton seed size has been reduced compared to sixty years ago. Planting smaller seeds is concerning due to having less energy for emergence as well as complicating the ginning process. Two row spacings, two planting patterns, and two cotton varieties were evaluated over eight site years from 2019-2020. The solid planting pattern produced a higher yield on a land area basis. In addition, two varieties, each with three seed counts, were planted at three seeding rates and evaluated over six site years from 2019-2020. Greater seedcotton yields were observed from larger seed sizes and higher seeding rates. Row spacing had no impact on yield but depending on input cost, a 2x1 skip pattern could be beneficial. Also, higher seeding rates and larger seeds maximized yields.

Call number: LD2668 .T4 1953 W48 / Master of Science

Call number: LD2668 .T4 1978 S31 / Master of Science

Call number: LD2668 .T4 1984 L624 / Master of Science

Individual clumps of the perennial grass Bouteloua gracilis from which 25% or 75% of neighbors had been removed to a radius of 50 cm displayed significantly higher biomass production over one summer than did control plants. Neighbor removal also resulted in increased tiller production and flowering as compared to control plants. These results clearly demonstrate the importance of competition to B. gracilis in this system. In contrast, significant differences in predawn leaf water potential were found on only two of four sampling dates during the growing season. On the driest sampling date, increased variability in leaf water potential within treatments obscured the effect of treatment, even though the difference in mean leaf water potential between 75% removal and control treatments (0.35 MPa) was quite high. On the wettest sampling date, all plants appeared well-hydrated, and there was only negligible difference among treatments. In a second study, I examined the effect of near neighbors on the fecundity of an annual herb, Machaeranthera tanacetifolia (Asteraceae). Fecundity was negatively related to the number of neighbors within a biologically meaningful neighborhood radius for both conspecific neighbors and grass neighbors in 1984, and for grass neighbors in 1985. However, in no case did neighbors explain more than 6% of the variance in fecundity of M. tanacetifolia, and most plants produced few or no seeds regardless of the number of neighbors. I present a simple graphical model in which competition from neighbors serves as a necessary but not sufficient condition for high fecundity; other factors must also be favorable if a plant is to be successful. Application of this model to my data revealed that the amount of area occupied by neighbors had an important effect on fecundity for the subset of the population for which other conditions were inferred to be most favorable. As other conditions became less favorable, neighbors became less relevant to fecundity. I then discuss these results in terms of a general model of the interacting effects of competition and other factors, and distinguish four possible classes of outcome.

No description available.

Call number: LD2668 .T4 1957 M56 / Master of Science

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