• 1993 Cotton Seed Treatment Evaluations

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Cottonseed was treated with several fungicide treatments in an effort to protect the seed and seedling from disease. Seed germination and vigor was evaluated in three Arizona locations; Maricopa, Marana, and Safford. Stand counts were taken on two separate dates after emergence and percent emergence was calculated. Among the three locations only one, Marana, showed significant differences among treatments. The highest percent emergence being seeds treated with Nu-Flow ND at a rate of 7.5 fl oz/cwt. The untreated control placed last in the ranking at this location.
    • Boll Sampling to Predict Lint Yield in Upland and Pima Cotton

      Unrah, Bryan L.; Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Giving a cotton (Gossypium spp.) producer a method to predict lint yield, would be a useful management tool. The objective of this study was to determine if relatively simple measurements could be made near cut -out which could be used to adequately estimate lint yield for Upland (G. hirsutum L.) and Pima (G. barbadense L.) cotton. Data and samples were collected from the nitrogen (N) management study at Maricopa Ag. Center from two N treatments which were imposed on both Upland (var. DPL 5415) and Pima (var. S-7) cotton. The treatments were no added N and N added on an as- needed basis. Twenty hard -green bolls from the first or second fruiting positions were collected from each plot on 19 August 1993. The number of bolls expected to reach maturity prior to crop termination were then determined from five randomly selected plants in each plot. Measurements on each boll collected included fresh weight, diameter, number of locks, number of seeds, and dry seed cotton weight. Plant population was determined from early season stand counts. Seed cotton per boll was most highly correlated to boll weight for DPL 5415 and for Pima S-7 it was most highly correlated with boll diameter. These respective parameters were then used in linear regression to predict seed cotton /boll. Lint yield calculated from the regression models (using boll weight or diameter) and yield calculated from means of the data collected agreed quit well. Predicted yields from regression analysis overestimated the actual Upland yield by about 730 lb lint /acre and under estimated Pima yields to within about 150 lb lint /acre. It appears that this procedure has the potential to estimate lint yields to within about 150 lb lint /acre. However the sampling scheme will he refined especially in regard to estimation of plants /acre and bolls /plant which should improve yield estimate accuracy.
    • Cotton Defoliation Evaluations, 1993

      Silvertooth, J. C.; Stedman, S. W.; Cluff, R. E.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Three field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Upland cotton. These experiments were conducted at Coolidge, Marana, and Safford and utilized defoliation treatments designed for their potential effectiveness finder cooler weather conditions commonly experienced later in the defoliation season and at higher elevations. The treatments employed also offer potentials for use in close proximity to urban areas due to not having offensive odors associated with them. All treatments showed promise in terms of effectiveness and the results provide a basis for use recommendations in 1994 as well further points of study in future experiments.
    • Dry Matter Accumulation by Upland and Pima Cotton

      Unrah, B. L.; Silvertooth, J. C.; Steger, A. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Several investigations of dry matter accumulation by Upland cotton (Gossvpium hirsutum L.) have been conduced, however no investigations of this type have included American Pima cotton (G. barbadense L.). We conducted a study to describe the total dry matter accumulation and partitioning of that dry matter into various plant parts for both Upland and Pima cotton. During the growing seasons of 1990, 1991, and 1992 at two south-central Arizona locations, both Upland (var. DPL 90) and Pima (var. S-6) cotton were grown. Beginning 14 to 20 d after emergence, whole cotton plants were removed and cotton plants were separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction, also included squares, flowers, immature bolls, and burs from mature bolls, Regression analyses was used to model nutrient uptake as a function of both days after planting (DAP) and heat units after planting (HUAP). Regression analyses indicated that HUAP was equally good, and in most cases superior to using DAP to model dry matter accumulation and partitioning within both Upland and Pima cotton. The general patterns of dry matter partitioning for Upland and Pima cotton are similar. However, Upland and Pima differ in the relative amount of dry matter incorporated into reproductive (bur, seed, and lint) and vegetative (leaf and stem) structures. Upland cotton produced 3527 lb /acre more total dry matter than Pima cotton. At the end of this study the vegetative /reproductive ratio for Upland was 83% compared to 70% for Pima. Upland was also more efficient at partitioning lint dry matter within the total dry matter of the reproductive structures. Dry matter incorporated into reproductive structures was 23% lint for Upland, compared to only 14% lint in Pima cotton. In summary, Upland placed more total dry matter into reproductive structures, and of the amount placed into reproductive structures, a greater proportion was incorporated into lint, when compared to Pima cotton.
    • Evaluation of a Feedback vs. Scheduled Approach to PIX Application

      Fletcher, D. C.; Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Lewis, E. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two field experiments were conducted in 1993 in Arizona to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to mepiquat chloride (PIX™) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments received no PIX applications due to plants lacking vegetative tendencies based upon height:node ratios (HNRs) and established baselines. Scheduled PIX applications ranged from 0.5pt. /acre to 0.75 pt./acre, and were applied at early bloom (approx. 1500 heat units after planting (HUAP), 86/55 °F threshold) and post early bloom (approx. 2000 HUAP). PIX treatments did consistently reduce plant heights compared to an untreated check. Statistically significant differences (P ≤ 0.05) in lint yield were observed among the treatments (feedback vs. scheduled)at the Safford location only. Evidence from these studies do reinforce the use of a feedback approach from the standpoint of conserving inputs and maintaining optimum growth control.
    • Evaluation of Date of Planting on the Yield of Several Upland Varieties at Marana, 1993

      Silvertooth, J. C.; Brown, P. W.; Norton, E. R.; Unrah, B. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A single field experiment was conducted in 1993 at Marana, Arizona (2,000 ft. elevation) to evaluate the response of three Upland cotton varieties to three dates of planting. Planting dates ranged from as early as 6 April to 11 May. Planting date was a significant effect for all varieties and revealed a substantial drop in yield with delays past 20 April in 1993, which corresponded to 568 heat units (HU, 86/55 °F thresholds) accumulated since 1 January.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1993

      Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two field experiments were conducted in Arizona in 1993 at two locations (Maricopa and Safford). Both experiments have been conducted for five consecutive seasons, with consistent plot locations. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima cotton. The experiments each utilized N management tools such as pre - season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. Results at both locations revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The effects of N fertility levels have been consistently evident in crop maturity and its relationship to lint yields.
    • Nitrogen, Phosphorus, and Potassium Uptake by Upland and Pima Cotton

      Unruh, B. L.; Silvertooth, J. C.; Steger, A. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Several investigations of nitrogen (N), phosphorus (P), and potassium (K) uptake by Upland cotton (Gossypium hirsutum L.) have been conduced, however no investigations of this type have included American Pima cotton (G. barbadense L.). We conducted a study to describe the total N, P, and K uptake and the partitioning of each nutrient into various plant parts for both Upland and Pima cotton. During the growing seasons of 1990, 1991, and 1992 at two south-central Arizona locations, both Upland (var. DPL 90) and Pima (var. S-6) cotton were grown. Beginning 14 to 20 d after emergence, whole cotton plants were removed and cotton plants were separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction, also included squares, flowers, immature bolls, and burs from mature bolls. The appropriate analyses for total N, P, and K were determined on each fraction (except lint). Regression analyses was used to model nutrient uptake as a function of both days after planting (DAP) and heat units after planting (HUAP). Regression analyses indicated that HUAP was equally good, and in most cases superior to using DAP to model total nutrient uptake and partitioning within both Upland and Pima cotton. In every case there was close agreement between the predicted and actual total nutrient uptake. For Upland cotton the actual total N, P, and K uptake was 199, 29, and 250 kg ha⁻¹ and the predicted total N, P, and K uptake was 199, 29, and 255 kg ha⁻¹, respectively. For Pima cotton the actual total N, P, and K uptake was 196, 29, and 215 kg ha⁻¹ and the predicted was 210, 29, and 229 kg ha⁻¹, respectively. The pattern of nutrient partitioning in Upland cotton were similar to the findings of others and Pima showed the same general patterns of partitioning as Upland cotton. Seeds were a major sink of nutrients. Nutrient uptake in seeds resulted in decreasing uptake in leaves and stems. Presumably, due to mobilization of nutrients from those parts to the seeds during seed development. The nutrient requirements to produce 100 kg lint ha' for Upland cotton was 15, 2.2, and 19 kg ha⁻¹ for N, P, and K, respectively and was 20, 3.0, and 22 kg ha⁻¹, respectively for Pima cotton.
    • Plant Population Evaluation for Upland Cotton

      Silvertooth, J. C.; Norton, E. R.; Stedman, S. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
    • Potassium Fertilization of Upland and Pima Cotton

      Unruh, B. L.; Silvertooth, J. C.; Galadima, A.; Clark, L. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      In a continuing effort to assess the agronomic necessity of potassium (K) fertilization in Arizona cotton (Gossypium spp.) production, one new and two on-going (Maricopa and Safford Ag. Centers), K fertility studies were conducted in 1993. They included locations ranging from western (Yuma) to eastern (Safford) Arizona, with both Upland (G. hirsutum L.) and American Pima (G. barbadense L.) cotton, using soil and foliar applications of K. The results indicated that there was no response to the added K at any of the locations by either Upland or Pima cotton.