• A Comparison of Three Cotton Tillage Systems: Six Year Summary

      Coates, Wayne E.; Thacker, Gary W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two reduced cotton tillage systems, both of which utilize controlled traffic farming techniques, were compared to a conventional tillage system in terms of energy requirements, field work time requirements, crop yield, and operating costs. Six seasons of testing show the Sundance system to have the lowest energy requirement of 31.95 Hp- Hr /Ac, the Uprooter -Shredder-Mulcher the second lowest at 47.16 Hp- Hr /Ac, and conventional tillage the highest at 66.89 Hp- Hr /Ac. Field work times of the two reduced tillage systems were about 58% that of conventional tillage. Costs of the two reduced tillage systems are lower than for conventional tillage. We have never measured a significantly lower lint yield with either of the two reduced tillage systems, relative to conventional tillage.
    • 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.
    • The Pegasus Rapid Plowdown System: A New Concept in Cotton Tillage

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      This new concept in tillage is to open a deep, temporary slot next to the cotton row and to insert the stalks and/or roots into the slot before the soil falls back in. The Pegasus Rapid Plow Down System is a relatively simple implement which offers good residue burial and reliability. Our limited field test data indicate that this invention requires less energy and field work time than conventional tillage systems.
    • 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.