Project Summaries

02-235AZ  Project Manager: D. C. Jones

ARIZONA UPLAND COTTON ADVANCED STRAINS TESTING PROGRAM

E.R. Norton, University of Arizona

Arizona Upland Cotton Testing Program

02-235AZ

E.R. Norton, D.L. Hatch, and K.F. Ellsworth
University of Arizona

Cotton Incorporated Project Manager: Don C. Jones

One of the most critical decisions cotton producers make each year is choosing which variety is best suited to their region and more specifically to their farm. With the advent of transgenic technologies and the quick development and release of varieties each year, that decision can be very difficult. Variety trial information produced by both the private and public sectors can help provide the information needed to make an informed decision.

The Arizona Upland Cotton Advanced Strains Testing Program conducted through the University of Arizona, with support from participating seed companies and Cotton Incorporated through the Arizona Cotton Growers Association State Support Committee, provides critical and unbiased information to the seed companies on the performance of varieties that will likely be grown in Arizona in subsequent years. It also provides the Arizona cotton industry with an unbiased view of plant materials that are being considered for commercialization prior to release into the public market place. This situation provides an opportunity to influence the decisions as to which varieties will be advanced for release, helping to ensure varieties with high yield potential and high fiber quality characteristics are available for the Arizona cotton growing industry. One of the unique aspects of this program is the range of conditions under which strains are evaluated. Three locations selected for testing range from slightly above sea level (100 ft, Yuma) to over 2800 ft. elevation (Safford), thereby providing a diverse set of climatic conditions for variety evaluation. This program provides an opportunity to evaluate the same variety across varied environments and to observe the effects of these conditions on plant growth and development, yield, and fiber quality.

Three separate field trials were conducted in 2012 across the cotton producing regions of Arizona. Locations included Yuma (130 ft above MSL), Maricopa (1170 ft. above MSL), and Safford (2900 ft above MSL). Plot dimensions were four rows wide and 38 feet in length. Row spacing varied among locations with 38, 40, and 42 inch row spacing at Safford, Maricopa, and Yuma respectively. All plots were arranged in a randomized complete block design with four replications. Plots were planted with 200 seeds per 40 feet of row length to achieve a plant population of 2-4 plants per linear foot. If populations were found to be higher, thinning crews were employed to achieve the desired population. In 2012 there was no need for plot thinning. Early season data, including stand counts and vigor rating, were collected within 2 weeks of planting or initial water-up irrigation. This data was used to calculate a population estimate and to evaluate seedling vigor. Plant growth and development data was collected at early bloom or slightly thereafter and just prior to harvest at each location to document crop vigor and progression towards cut-out giving an indication of relative maturity. Data collected included plant height and nodes above white flower (NAWF). Final plant height data was also collected from each entry near harvest time. Yield was estimated by harvesting the center two rows of each experimental unit and weighed with a hanging basket equipped with load cells. A large grab sample (approximately 6-8 lbs.) was also collected from each experimental unit from which percent lint was determined by ginning the sample on a small research gin at the Maricopa Agricultural Center. Fiber quality was determined by the USDA-AMS cotton classing office in Visalia, CA. A premium or discount for each entry was then calculated based upon fiber quality data and the USDA CCC (Commodity Credit Corporation) loan schedule. This premium/discount was applied to a base price of 52 cents per pound and a final crop value was calculated by multiplying the base price plus the premium/discount by the total lint yield of the entry. All data collected was summarized and analyzed according to statistical procedures as outlined by the SAS Institute.

Planting conditions experienced in the Yuma area during the time of planting and stand establishment were excellent. Plots were planted March 20. Conditions facilitated establishment of a uniform and healthy stand of cotton throughout the plots. Average plant density was 3.1 plants per foot with an average vigor rating of 5.1 on a scale of 1-9. Early bloom data was collected on June 21. Significant variation in plant height existed at this stage of the season with a range of approximately 35 to 45 inches. Values for NAWF also varied from 7 to slightly less than 10. This is a good indication of relative maturity of the variety. Final plant height ranged from 41 to 65 inches. Final irrigation occurred in early August with initial defoliation on 18 August. Plots were harvested on 12 September. Cooler than average summer temperatures during the peak bloom period resulted in high fruit retention levels and high yield potential. The first two weeks of August turned extremely hot, but the crop had matured by that time and was not adversely affected by the heat stress. High temperatures at this point in the season helped to facilitate an efficient defoliation. Yield in this trial ranged from a low yield of 1442 lbs lint/acre to slightly over 2000 lbs lint/acre. Significant differences were observed in lint yield estimates with a least significant difference of 303 lbs. Statistically significant differences also were observed in percent lint values and every fiber quality parameter measured with the exception of percent uniformity. Only one entry evaluated at Yuma produced fiber that fell in the discount range. This discount was associated with leaf grade, which is typically a result of poor defoliation and not necessarily associated with fiber properties. Eight of the 26 entries evaluated in Yuma during 2012 performed better than average in terms of both lint yield and fiber quality.

Plots were established at the Maricopa Agricultural Center on 20 April and irrigated on 23 April. Excellent weather conditions at the time of planting resulted in uniform stands and healthy seedlings. On average, initial evaluations of plant stand demonstrated a plot population of 3.8 plants per linear foot of row. Seedling vigor estimations averaged 6.1 on a scale of 1-9 with 9 being the highest. No issues related to seedling disease were observed in any of the plots during establishment. Plant growth was significantly different among entries. Range in average plant height was 23 to 29 inches. A range of NAWF values was observed at early to mid-bloom with the lowest of 6.2 to slightly under 9.5. This range indicates significant differences in relative maturity among the varieties tested. Final plant height at this location ranged from 38.5 to 53.9. Plots received a final irrigation on 21 September. Irrigation was extended two weeks later than normal in an effort to complete development of green bolls associated with some of the later maturing varieties. Initial defoliation was 9 November and received a total of three defoliation applications in an effort to achieve adequate leaf drop and to open as many mature bolls as possible. Cooler temperatures during this time made efficient and adequate defoliation difficult. These conditions resulted in higher than normal leaf grade scores in the fiber quality data. Relatively cooler summer temperatures resulted in lower than normal heat stress through late July. The first two weeks of August experienced high temperatures and significant levels of heat stress. However, this did not appear to negatively impact final yield. Range in lint yield was 1146 to 2521 lbs of lint yield per acre with an average yield of 1791. Statistically significant differences were observed in lint yield with a least significant difference of 356 lbs. Percent lint turnout was also significantly different among varieties. All fiber quality parameters measured resulted in statistically significant differences among varieties evaluated. Four of the entries evaluated produced fiber that received a discount as a result of leaf grade scores. Average leaf grade for this trial was 3 with some entries receiving leaf grade scores of 6 and 7. This is a direct result of the difficulty experienced in achieving adequate defoliation. Difficulty in defoliation was observed generally in commercial fields throughout the region when defoliation was initiated in the early part of November. No other measured fiber quality parameter fell within the discount range for any of the varieties tested. Seventeen of the 42 entries tested in this trial performed better than average in terms of both lint yield and fiber quality.

Plots were established at the Safford Agricultural Center on 19 April. This is the only one of the three sites planted into moisture and not irrigated to initiate germination. Weather conditions surrounding the planting date were optimum with warm soil temperatures resulting in good germination with the exception of a few plots that were compromised in one replication due to soil moisture conditions at planting. The plots were eliminated from the analysis and statistical procedures were used to correctly analyze the data. Average plant spacing at the Safford location was 2.5 plants per foot and an overall average seedling vigor rating of 5.9. Plant height at early bloom ranged from 18.5 inches to slightly over 25 inches. Differences in NAWF values were observed among varieties and ranged from 6.6 to 9.6. Final plant height ranged from 25.7 to 41.7 inches. Conditions experienced by the crop during the growing season were optimum for high yield. Plots received the final irrigation on 8 September and were defoliated with a one-time application on 13 October. Warm conditions at the time of defoliation resulted in effective and efficient leaf drop and boll opening. Plots were harvested on 15 November. Statistically significant differences in lint yield were observed among varieties tested with a LSD of 360 lbs. lint per acre. Yields ranged from 985 to slightly under 2000 lbs. lint per acre. Differences associated with percent lint were statistically significant and ranged from 30 percent to slightly over 41 percent. This was the largest range in percent lint observed among the three locations. Significant differences among varieties for each of the fiber quality parameters measured were also observed. Of the 42 varieties evaluated at the Safford location in 2012, 11 produced higher than average lint yield and fiber quality.

Several new varieties performed very well at all three locations in 2012 which is a good indication that we continue to move in the right direction in terms lint yield and fiber quality. Several of the entries that performed well in Arizona in 2011 and 2012 as experimental varieties were advanced in 2012 or will be advanced by the seed companies in 2013 into commercial production. We will continue with this evaluation of recently released and experimental varieties in Arizona in 2013 in an effort to find varieties that continue to raise the bar with respect to yield and fiber quality expectations for the Arizona cotton industry.

 

Project Year: 2012
 

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