Cotton Report 2001
ABOUT THE COLLECTION
The Cotton Report is one of several commodity-based agricultural research reports published by the University of Arizona.
This report, along with the Forage and Grain Report, was established by Hank Brubaker, Extension Agronomist, after seeing a similar report published by Texas A&M University in the mid-1970’s.
The purpose of the report is to provide an annual research update to farmers, researchers, and those in the agricultural industry. The research is conducted by University of Arizona and USDA-ARS scientists.
Both historical and current Cotton Reports have been made available in the UA Campus Repository as part of a collaboration between the College of Agriculture and Life Sciences and the University Libraries.
Contents for Cotton Report 2001
- Planting Date Effects Crop Growth and Yield of Several Varieties of Cotton, Marana 2000
- Evaluation of Irrigation Termination Effects on Fiber Micronaire and Yield of Upland Cotton, 2000
- Evaluation of Crop Management Effects on Fiber Micronaire, 2000
- Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 2000
- Recent Yield and Fiber Micronaire Tendencies for Upland Cotton in Arizona
- Heat Stress and Cotton Yields in Arizona
- 2000 Low Desert Upland Cotton Advanced Strains Testing Program
- Arizona Upland Cotton Variety Testing Program, 2000
- Upland Cotton Regional Variety Trial, 2000
- Short Staple Variety Trials, Graham County, 2000
- Short Staple Variety Trials in Cochise County, 2000
- Acala Cotton Variety Trial, Safford Agricultural Center, 2000
- Short Staple Variety Trial in Virden, NM, 2000
- Effects of High Frequency Irrigation on Irrigation Uniformity III
- Evaluation of a Drip Vs. Furrow Irrigated Cotton Production System
- Nitrogen Management Experiments For Upland and Pima Cotton, 2000
- Summary of Nitrogen Management Experiments in Irrigated Cotton
- Soil and Plant Recovery of Labeled Fertilizer Nitrogen in Irrigated Cotton
- N Volatilization from Arizona Irrigated Waters
- Evaluation of Potassium and Phosphorus Fertility in Arizona Soils
- Influence of Ironite and Phosphorus on Long and Short Cotton on the Safford Agricultural Center, 2000
- Evaluation of a Calcium-Based Soil Conditioner in Irrigated Cotton
- Soil Amendment Study on Long and Short Staple Cotton, Safford Agriculture Center, 2000
- Cotton IPM in Arizona: A Decade of Research, Implemention & Education
- Pest and Pesticide Usage Patterns in Arizona Cotton: Final 2000 Date
- Bollgard® and Bollgard II® Efficacy in Near Isogenic Lines of 'DP50' Upland Cotton in Arizona
- Mortality and Development Effects of Transgenic Cotton on Pink Bollworm Larvae
- Arizona's Multi-agency Resistance Management Program for Bt Cotton: Sustaining the Susceptibility of Pink Bollworm
- Relative Susceptibility of Whiteflies to Danital® + Orthone® Over a 5-year Period
- Sustaining Arizona's Fragile Success in Whitefly Resistance Management
- Honeydew Production by Sweetpotato Whitefly Adults and Nymphs
- Silverleaf Whitefly Studies: Effects of Trichome Density and Leaf Shape
- Cost-Effective Lygus Managment in Arizona Cotton
- Cotton Aphid Biology and Honydew Production
- Insecticide Evaluation Studies, Safford Agricultural Center, 1999-2000
- Agronomic and Economic Evaluation of Ultra Narrow Row Cotton Production in Arizona 1999-2000
- Evaluation of Narrow and Ultra Narrow Cotton in Arizona
- Continuing Investigations in Ultra-narrow Row Cotton, Safford Agricultural Center, 2000
Copyright © Arizona Board of Regents. The University of Arizona.
Nematodes and Their Control in Upland Cotton(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Cotton fields from 133 townships in 7 Arizona counties were surveyed for nematodes. Plant parasitic species were found in all fields sampled. Lesion nematodes (Pratylenchus spp.) were found in 33% of the samples and Root-knot nematodes (Meloidogyne spp.) were found in 35% of the samples. Field trials in Pinal Coiunty were conducted in 1998, 1999, and 2000 to determine the impact of nematode control on the yield of Upland cotton. Telone II® increased lint production in 20 of 24 trials.
Continuing Investigations in Ultra-narrow Row Cotton, Safford Agricultural Center, 2000(College of Agriculture, University of Arizona (Tucson, AZ), 2001)The continuing investigation in ultra-narrow row cotton production has not produced a definitive answer to whether this practice would be economically feasible in this area. Results of this season showed that planting two seed rows on a bed can produce yields in excess of those yields produced with a single seed row, where the plant populations are comparable. This configuration can be harvested with a conventional spindle picker. Plant mapping data and HVI data are shown for all treatments in this study.
Evaluation of Narrow and Ultra Narrow Cotton in Arizona(College of Agriculture, University of Arizona (Tucson, AZ), 2001)A field experiment was conducted in 2000 to evaluate narrow (30") and ultra narrow (10") row spacing cotton production systems. The study was conducted at a commercial farm located near Buckeye, AZ. The experimental design was a randomized complete block with three replications. The treatments included 10" row spacings that were harvested with a finger stripper, 30" row spacings harvested with a brush stripper, and 30" row spacings harvested with a spindle picker. Plant growth and development was not affected by row spacing throughout the growing season. No significant difference was observed for lint yield however, gin turnout was slightly lower for stripper harvested treatments. Fiber quality measurements were similar for both row spacing with the exception of fiber micronaire which was lower in stripper harvested treatments. Bark was a major problem with stripper harvested treatments with at least 92% of bales receiving a discount compared with 36% of spindle harvested bales.
Agronomic and Economic Evaluation of Ultra Narrow Row Cotton Production in Arizona 1999-2000(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Ultra Narrow Row (UNR) and conventional (CNV) cotton production systems were compared with respect to agronomic practices, yield, fiber quality, and production costs in experiments conducted in 1999 and 2000 in central Arizona. Cotton rows were 10 and 40 inches apart in the UNR and CNV systems, respectively. In 1999, the average lint yield in the UNR system, 1334 lb/A, was significantly greater than the 1213 lb/A yield of the CNV system. Similar results were obtained in 2000 with yields of 1472 and 1439 lb/A for the UNR and CNV systems, respectively. Fiber grades of both systems were comparable with most bales receiving a grade of 21 in 1999. The average bale grades in 2000 were 11 and 21 in the UNR and CNV systems, respectively. The quality of the fiber produced in both systems was also comparable with staple and strength measurements meeting base standards in both years. However, there was a consistent difference between the UNR and CNV systems in both years with respect to micronaire. Micronaire averaged 4.5 and 4.0 in the UNR system in 1999 and 2000, respectively, and 5.0 and 4.9 in the CNV system in 1999 and 2000, respectively. Variable growing costs were $607 and $446 for the UNR system in 1999 and 2000, respectively, and $660 and $519 for the CNV system in 1999 and 2000, respectively. Harvest and post-harvest variable costs were $234 and $209 in the UNR system in 1999 and 2000, respectively, and $217 and $224 in the CNV system in 1999 and 2000, respectively. The economic data indicated that the UNR system reduced production costs and increased profitability without sacrificing lint yield or quality. However, these experiments also indicated that many production challenges such as planting and obtaining adequate plant populations, managing plant height control, and weed control need further study.
Insecticide Evaluation Studies, Safford Agricultural Center, 1999-2000(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Three studies were conducted over the two year period to explore the effectiveness of using pyrethroid insecticides only vs. rotating insecticide chemistries between the pyrethroids and organophosphates on both long and short staple cotton varieties. These same treatments were also evaluated over Bt and non-Bt varieties. In the worst case scenario, where weather conditions prevented timely application of insecticides and effectiveness of insecticides applied, long staple cotton yielded around 1/3 bale per acre after six insecticide applications. Within 200 feet of this experiment, during the same cropping season, with the same insecticides applied, DP 90B (a Bt variety) produced 3 bales per acre. Details of these studies are contained in this report.
Cotton Aphid Biology and Honydew Production(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Cotton aphid, Aphis gossypii Glover, fecundity, nymph development and honeydew production were studied in the laboratory. Apterous adult females produced an average of 1.7 nymphs per day and the nymphs (four instars) developed to adults in an average of 4.1 days at 26.7° C in the laboratory. Average longevity of adults was 16.1 days. More honeydew drops were produced by one-day old nymphs than three- or four-day old nymphs. Numbers of honeydew drops produced on a day to day basis were highly variable and did not show a distinct pattern of production. More honeydew drops, sugars and progeny were produced by adults at 26.7° C compared with 15.6 or 32.2° C. Increasing times of exposure of clean cotton lint to aphids and the resulting increasing amounts of honeydew sugars under laboratory and field conditions were significantly related to increasing cotton lint stickiness as measured with a thermodetector.
Cost-Effective Lygus Managment in Arizona Cotton(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Timing sprays for maximum return on investment requires sampling and counting both Lygus adults and nymphs in a minimum of 100 sweeps. Once at least 15 total Lygus and 4 nymphs per 100 sweeps are detected, sprays for Lygus should be made. This '15/4' regime should protect yields, moderate spray frequency and costs, and maximize profit. Economic thresholds are impacted by the prevailing economic conditions such as lint value and costs of control; however in this case, the relationship that maximizes returns was not changed when varying these parameters well beyond market standards. A key finding of these studies is that aside from profits, yields plateau prior to the more aggressive treatment regimes. This phenomenon, where more protective approaches result in yield reductions, occurred in all three years of study (1997, 1999, 2000). This signals the importance of optimizing inputs so that sprays are made only when indicated by sampling and once the 15/4 level is reached, but no sooner. More aggressive approaches by definition cost more money to maintain, but also have some probability of lowering yields while risking secondary pest outbreaks. The specific mechanism for this yield decline is unknown at this time. At the other end of the spectrum, delaying action beyond the 15/8 action threshold risks economic yield loss and reductions in quality, especially color grade and micronaire. While this work definitively establishes the relative importance of Lygus nymphs to yield loss and to the need for action, the conditions under which these tests were carried out are limited to in-season infestations of Lygus. Further work is necessary to better quantify change in the action levels according to plant phenology and other plant-based factors (e.g., plant population, fruit retention, plantwater status, etc.). Early season infestations may respond differently to the action levels proposed, and it is expected that later season populations of Lygus pose far less damage potential when square populations and retention are very low.
Silverleaf Whitefly Studies: Effects of Trichome Density and Leaf Shape(College of Agriculture, University of Arizona (Tucson, AZ), 2001)We examined nine upland cotton cultivars in 2000 to determine silverleaf whitefly (SLW)-cotton leaf trichome relationships. The hairy leaf cultivar Stoneville 474 had significantly higher numbers of SLW eggs, nymphs and adults compared to eight other smooth leaf cotton cultivars. The top young leaves on main stem terminals had fewer SLW eggs, nymphs and adults, but higher numbers of trichomes compared with older leaves. Among the eight smooth leaf cultivars, the four okra leaf cultivars as a group had fewer SLW eggs, nymphs and adults compared with the four normal leaf cultivars.
Honeydew Production by Sweetpotato Whitefly Adults and Nymphs(College of Agriculture, University of Arizona (Tucson, AZ), 2001)We determined honeydew production by male and female sweetpotato whiteflies and the effects of temperature on honeydew production of each sex. We also determined honeydew production by each nymphal instar. Overall, adult SPW produced more honeydew than nymphs. Adult females produced more honeydew than males. The relative differences between honeydew production for males and females and between amounts adults produced compared with nymphs were consistent. However, honeydew production by adult and nymph individuals was subject to large degrees of variation.
Sustaining Arizona's Fragile Success in Whitefly Resistance Management(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Arizona cotton experienced a severe crisis in 1995 stemming from resistance of whiteflies to synergized pyrethroid insecticides. The insect growth regulators (IGRs), Knack® (pyriproxyfen) and Applaud® (buprofezin), served a pivotal role in resolving this problem. Similarly, Admire® (imidacloprid), the first neonicotinoid insecticide to obtain registration in Arizona, has been the foundation of whitefly control in vegetables and melons. In this paper we provide an update regarding the susceptibility to key insecticides of whiteflies from Arizona cotton, melons, and greenhouses. Overall, whitefly control in Arizona cotton remained excellent in the 2000 season and there were no reported field failures. However, there was a significant decrease in susceptibility to Applaud of whiteflies collected from cotton. One collection from Eloy, Arizona, in 2000 had susceptibility to Applaud that was reduced 129-fold relative to a reference strain. Whiteflies resistant to Knack, detected for the first time in Arizona in 1999, were again detected in 2000 but at lower frequencies than in 1999. Though whiteflies resistant to Admire/Provado® continued to be found at specific locations, overall susceptibility to Admire/Provado in 2000 remained high in whitefly collections from cotton. The new neonicotinoid insecticides, thiamethoxam and acetamiprid, were similar in toxicity to Arizona whiteflies in laboratory bioassays and we confirmed the significant but relatively low-order cross-resistance we previously reported between these neonicotinoids and Admire/Provado. Arizona whiteflies continued to be relatively susceptible to mixtures of Danitol® (fenpropathrin) and Orthene® (acephate). Factors that could undermine the current success of whitefly resistance management in Arizona are discussed. These include: 1) more severe resistance to IGRs in whiteflies from cotton, stemming from increased IGR use within and outside of cotton; 2) resistance of vegetable, melon and greenhouse whiteflies to the various formulations of imidacloprid (Admire, Provado, Merit®, Marathon®); 3) the imminent registration of new neonicotinoid active ingredients in cotton, greenhouses and other Arizona crops.
Relative Susceptibility of Whiteflies to Danital® + Orthone® Over a 5-year Period(College of Agriculture, University of Arizona (Tucson, AZ), 2001)As part of a program to assess differences in susceptibility to insecticides among regional populations of Bemisia tabaci, insecticide resistance monitoring was carried out at the Maricopa Agricultural Center from fall, 1995 through 1999. Monitoring efforts were concentrated on Danitol®+Orthene® following reports of control problems and documentation of resistance to this mixture in 1995. We were interested in the longer-term dynamics of resistance in light of radically altered treatment regimens beginning with the use of IGRs in 1996. Although the frequency of susceptible individuals to Danitol+Orthene tended to increase in the later years, highly resistant individuals were still present 5 years after the resistance episode of 1995. Whitefly adults collected from various insecticide treatment plots other than Danitol+Orthene were generally uniform in their responses from the time of initial whitefly infestation until defoliation. However, a dramatic shift in susceptibility occurred following a single application of Danitol+Orthene in 1997 and 1999. The increased frequency of resistant individuals following treatment suggests that any large scale return to the use of Danitol+Orthene could rapidly select for proportionally higher numbers of resistant whiteflies and perhaps reduced control in cotton fields.
Arizona's Multi-agency Resistance Management Program for Bt Cotton: Sustaining the Susceptibility of Pink Bollworm(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Bt cotton has been used in Arizona since 1996 with exceptionally positive results in terms of economic returns to growers and reductions in insecticide use in cotton. Yet, the isolation of pink bollworm highly resistant to Bt cotton from collections made in Arizona in 1997 demonstrated the seriousness of the threat that resistance poses to transgenic Bt technology. For this reason unparalleled measures have been taken to detect and manage resistance of pink bollworm to Bt cotton in Arizona. This paper presents results of statewide monitoring of pink bollworm susceptibility to the Bt toxin, Cry1Ac, conducted from 1997 to 1999. Mean susceptibility of Arizona pink bollworm to Cry1Ac increased from 1997 to 1999. Mean corrected mortality in 1μg/ml Cry1Ac assays was 52.3% in 1997, 90.6% in 1998, and 97.9% in 1999. Mean corrected mortality in bioassays of 10 μg/ml was 94.5% in 1997, 99.8% in 1998, and 100% in 1999. Selection with Cry1Ac in the laboratory has produced from 1997 field collections a strain possessing 200 to 900-fold resistance to Cry1Ac. This resistant strain is capable of surviving on Bt cotton. We provide an overview of other components of the multi-agency collaboration to sustain efficacy of Bt cotton in Arizona. These include: 1) evaluation of the field performance of Bt cotton; 2) mapping and analysis of use of Bt and non-Bt cotton and compliance with refuge requirements; 3) effectiveness of internal versus external refuges and movement of pink bollworm moths from refuges; and 4) activities of the Arizona Bt Cotton Working Group to formulate and implement effective resistance management strategies.
Mortality and Development Effects of Transgenic Cotton on Pink Bollworm Larvae(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Pink bollworm (PBW), Pectinophora gossypiella (Saunders), larval mortality after different times of confinement on NuCOTN 33B® (Bt) cotton bolls were compared with larval mortality on Delta and Pineland 5415 cotton bolls as controls. We also compared larval mortality on different age cotton fruiting forms and determined the Bt susceptibility of different age PBW larvae. Infesting Bt bolls with PBW eggs that hatched within 24 h resulted in 92% larval mortality after 48 h and 100% mortality in 4 days or longer. There were no differences between cultivars in numbers of larval entrances holes into bolls. Generally, days to pupation for both males and females were longer on Bt bolls compared with non-Bt cotton. There were no significant mortality differences for larvae feeding on Bt fruiting forms of different ages ranging from one-half grown flower buds to 40-day old immature green bolls.
Bollgard® and Bollgard II® Efficacy in Near Isogenic Lines of 'DP50' Upland Cotton in Arizona(College of Agriculture, University of Arizona (Tucson, AZ), 2001)The Cry1Ac gene (Bollgard®) is available in cotton either alone ('B') or in combination (Bollgard II®) with a second gene, Cry2Ab ('X'). We evaluated these two different transgenes, separately and together, in near isogenic lines of the upland cotton variety ‘DP50’. DP50B was previously transformed with the Cry2Ab gene to give rise to the experimental line 985BX which was then back-crossed to DP50 to produce near isogenic single gene variants, 985B and 985X. The lepidopteran target was pink bollworm (PBW), Pectinophora gossypiella (Saunders), which was evaluated in two field studies through a series of samples from artificially and naturally-infested bolls. In one study (NTO), three cotton lines (DP50, DP50B, 985BX) were evaluated under three spray regimes. In the second study (Isoline), five near isogenic lines (DP50, DP50B, 985B, 985X, 985BX) were evaluated under two spray regimes: fully sprayed and lepidopteran unsprayed. In lines containing only one transgene, Cry1Ac or Cry2Ab, bolls had consistently fewer PBWs than the non-Bt variety. Very few PBWs developed into large (3rd instar) larvae in these Bt varieties. The majority (NTO: 83%; Isoline: 94%) of PBWs recovered were dead first instar larvae. Less than 5% of the DP50B bolls in the NTO study were infested with feral large (≥3rd instar) larvae, and large larvae were present in less than 2% of naturally-infested bolls of single-gene lines in the Isoline study. PBW age and mortality distributions confirmed that the single transgenes were effective in stopping PBW development and killing young instars. Cry2Ab displayed a broader spectrum of efficacy as it was significantly more effective against citrus peelminer (Marmara spp.), an incidental lepidopteran present in high densities in the tests. The two-gene (Cry1Ac + Cry2Ab) line showed better (at least 10-fold) efficacy than the single-gene lines against PBW large larvae infestation. The PBW age distributions found in this variety consisted almost entirely (98%) of dead first instar larvae. Less than 0.6% of the bolls of the two-gene variety in the NTO study were infested with large (≥3rd instar) larvae, and there was no infestation by large larvae in any of the naturally-infested bolls in the Isoline study. Yields and other agronomic parameters of the two-gene and single-gene varieties were superior or similar to the null parent. Second pick yields of all Bt varieties were significantly higher than the recurrent parent non-Bt line, suggesting a high degree of efficacy against typically high PBW densities during the late season. Cotton lines with transgenes (Cry1Ac & Cry2Ab) separately and combined demonstrated a high degree of efficacy and agronomic performance for usage in Arizona against PBW. The ramifications of isogenic comparisons of PBW incidence on efficacy and resistance monitoring are discussed.
Pest and Pesticide Usage Patterns in Arizona Cotton: Final 2000 Date(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Arizona's pesticide use reporting (PUR) database is used to track and quantify the general decline in pesticide use in the state. A full summary of the official 2000 growing season pesticide usage is included. The database also enables tracking of changing usage patterns. For two years, target pest information has been included in the Arizona PUR database. Limitations in the PUR database are discussed. The reporting coverage shortfall for insecticide reports in the PUR database is estimated and found to be reasonable relative to sample based approaches to pesticide use reporting.
Cotton IPM in Arizona: A Decade of Research, Implemention & Education(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Cotton production in Arizona has been faced with major challenges in insect control during the past decade. These challenges have been met through IPM programs of research, implementation, and education. The decade began (1990) with an outbreak of our key lepidopteran pest, the pink bollworm. Growers sprayed for all pests more than 11 times at a cost of over $113 / A that year. The following years (1991–1995) saw the introduction of and devastation by a serious, quality-reducing insect, the sweetpotato or silverleaf whitefly. Growers sprayed up to 6.6 times (1995) at a cost of over $145 / A to combat this single insect pest. The cotton IPM program at the University of Arizona along with industry, grower, and USDA partners readied farmers for the introduction (1996) of two strategic sets of pest control technology, ‘Bt’ transgenic cotton and insect growth regulators (IGR). Through an aggressive educational campaign, growers learned about the safe, effective, and sustainable use of these technologies. As a result, cotton growers saw their average spray requirement plummet from 12.5 sprays at $217 / A (1995) to an historic low of 1.91 sprays at $37 / A (1999). Now new threats from an old pest, Lygus bugs, pose serious challenges to these staggering advances in cotton IPM. This paper highlights the key advances made in research, implementation, and education during this volatile decade. Furthermore, we conclude with one example how systematic, large-scale, and long-term research can provide insight into the role that new technology and the knowledge to use it properly have on cotton grower and industry success.
Soil Amendment Study on Long and Short Staple Cotton, Safford Agriculture Center, 2000(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Two soil amendments, Agriblend Plus and Superfloc A-836, were applied to cotton beds prior to planting at rates of 5, 10, 15 and 20 pounds per acre, incorporated and planted to short staple (DP 655BR) or long staple (HTO) cotton. The experimental plots were fertilized, irrigated and managed in a manner to produce optimal cotton yields. No statistically significant yield increases were seen from any of the treatments, even though a few interesting trends were observed. The report contains observations on plant mapping and lint quality data, in addition to yield data.
Evaluation of a Calcium-Based Soil Conditioner in Irrigated Cotton(College of Agriculture, University of Arizona (Tucson, AZ), 2001)A two site evaluation of a calcium (Ca²⁺)-based soil conditioner was conducted during the 1999 cotton season. The two locations included one at the Maricopa Agricultural Center (MAC) in Maricopa, AZ and the other was on a grower-cooperator field in Tacna, AZ. Both studies involved the use of CN-9, a Ca-nitrate solution with 9% nitrogen and 11% Ca. At MAC theCN-9 solution was sprayed over the seedbed post planting but prior to the first water-up irrigation. At the Tacna site CN-9 was applied in a sidedress application at planting. Routine plant measurements were taken throughout the duration of both studies and lint yield estimates were made at each location at the end of the season. No significant differences due to the application of CN-9 were detected in any data collected.
Influence of Ironite and Phosphorus on Long and Short Cotton on the Safford Agricultural Center, 2000(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Ironite and phosphorus were applied as a combined treatment and also individually to plots planted to long and short staple cotton to find their effect on crop development and lint yield. A statistically significant increase in lint yield was seen with 14 pounds of Ironite and 200 pounds of 16-20-0 per acre compared with the untreated check in the short staple plots. An increase in long staple yield was observed as the Ironite treatment increased from 7 to 28 pounds per acre when coupled with 200 pounds of 16-20-0. Few differences were seen between treatments in any of the plant mapping variables measured or with HVI values. More research and an economic analyses are needed to determine if this would be a recommended procedure in the Safford valley.
Evaluation of Potassium and Phosphorus Fertility in Arizona Soils(College of Agriculture, University of Arizona (Tucson, AZ), 2001)Two field experiments were conducted during the 2000 growing season to address fertility recommendations for fertilizer phosphorus (P) and potassium (K). A K fertility study was conducted near Tonopah, AZ consisting of two treatments, an untreated control and a treatment receiving a total of 20 gallons of K-Sul/acre. No significant differences were observed in leaf blade K concentrations between treatments. Plant growth and development estimates revealed that fruit retention (FR) levels remained consistently higher in the untreated control versus the treated plots. A second study involved treatments consisting of both P and K fertilizers was conducted near Cibola, AZ. Four treatments in this experiment included an untreated control plus treatments of 11-52-0, 0-0-60, and 4-17-40 at 100, 200, and 300 lbs. fertilizer/acre respectively. Plant growth and development estimates were similar among treatments during the season. At the end of the season the untreated control had a slightly higher FR level than the other treatments, which also produced a significantly higher yield. No other differences in yield among the fertilized treatments were observed.