With controlled traffic tillage, the field is divided into "traffic zones" to which all wheel traffic is confined and `production zones" where the plants are grown and there is no wheel compaction. Researchers have shown that using this concept can result in significantly lower tillage costs and field work time than with conventional "broadcast" tillage systems. Most researchers have shown that controlled traffic cotton yields are as high, and are sometimes higher than with conventional tillage. In our research, we have not measured any differences in yield or soil compaction between controlled traffic and conventional tillage systems.

Two field experiments were conducted in Arizona in 1992 at two locations (Maricopa and Safford). 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 were evident in crop maturity and its relationship to lint yields.

The computer program AZSCHED, with weather data obtained from AZMET, was used to schedule irrigations for a yield trial of Upland Cotton (DPL 90) at the Maricopa Agricultural Center. Cotton lint yields were compared between plots from eight treatments involving the combination of two irrigation efficiencies (70% and 90%), two nitrogen fertilizer placements (sidedressed and broadcast), and two phosphate fertilizer applications (0#/a and 50#/a). A potassium bromide (KBr) tracer was applied to select areas in each plot prior to the first irrigation. The total amount of fertilizer as nitrogen applied in split applications to both the sidedressed and broadcast plots was 120 #/a. The average amount of water applied to the plots were 33.5" for 70 % efficiency and 26.9" for 90% efficiency. Soil samples from each KBr applied plot were taken to a depth of 10' for analysis of bromide and nitrate to determine the depth of water movement through the soil profile. The plots were harvested on October 7, 1992. This year there was no significant difference in lint yield between any of the treatments: irrigation efficiencies, nitrogen placement, or phosphorous application.

A replicated field study was conducted at the Maricopa Agricultural Center in 1992 investigating Upland cotton lint yield and fiber quality response to foliar applied potassium thiosulfate. Applications were applied at early, peak, and late bloom. There were no significant yield or lint quality response by treatment.

Two reduced cotton tillage systems, both of which utilize controlled traffic farming techniques, are being compared to a conventional tillage system in terms of energy requirements, field work time requirements, crop yield, and operating costs. Four seasons of testing show the Sundance system to have the lowest energy requirement of 28.2 HpHr /Ac, the Uprooter-Shredder-Mulcher (USM) the second lowest at 40.5 HpHr /Ac, and conventional tillage the highest at 54.4 HpHr /Ac. Field work times of the two reduced tillage systems are about one-half 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.

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.

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.

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.

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.

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.