Most of the variety trial locations are on research stations throughout the state; trials that are planted on commercial farms give an added dimension to the results. While on-farm trials present logistical obstacles to researchers and to producer-cooperators, data from these trials give an important indication of how varieties will perform in "real world" situations. The authors wish to express their appreciation to the Mississippi cotton producers who allowed us to grow these variety trials on their farms and often put up with the aggravation of farming around small-plot research:
Frank Mitchener, Sumner Keys Arnold, Tunica Mark and Louis Fratesi, Elizabeth Boyd Eifling, Percy
Variety selection is one of the first, and perhaps the single most important, decisions a cotton producer makes each season. This bulletin is intended to be an aid in making this crucial decision. Certain data will also be of interest to ginners, millers, and other sectors of the cotton industry. The varieties reported on in this bulletin were submitted by the cotton seed companies listed on previous pages. A total of 48 varieties in the Delta and 37 varieties in the Hills were evaluated.
Due to the large and growing number of cotton varieties being evaluated, those submitted for testing were divided into two groups based on maturity classifications determined by the companies submitting each variety. The Early Maturing Cotton Variety Test was comprised of 32 varieties in the Delta and 26 varieties in the Hills. The Mid-Season Cotton Variety Test was comprised of 17 varieties in the Delta and 12 varieties in the Hills. Stoneville LA 887 and Deltapine 50 were used as check varieties in tests of both maturity groups.
The Early Maturing and Mid-Season Variety Tests were conducted at four locations in the Delta: Stoneville, Tunica, Sumner, and Elizabeth. Elizabeth was a new location on a Sharkey clay soil, chosen to replace a mixed soil site formerly used at Stoneville. The Early Maturing and Mid-Season Tests were conducted at five Hill locations: Mississippi State, Brooksville (planted on 30-in. rows), Raymond, Holly Springs, and Verona.
With the exception of the tests at Brooksville, all tests were planted solid in 38- or 40-inch rows. Each variety was replicated six times at each location except the Early Maturing Test at Holly Springs, where four replications were used. Yield determinations were based on the weight of seed cotton mechanically harvested from two-row plots that ranged from 40 to 50 feet in length. Determination of lint percent, boll size, seed index (weight in grams of 100 fuzzy seed) and fiber properties were made from hand-harvested, laboratory- ginned 100-boll samples from two replications at each location. HVI fiber property determinations were made by the Cotton Fiber Laboratory of Louisiana State University, Baton Rouge, LA. In addition, large, machine-harvested samples were obtained from the tests at Stoneville, Elizabeth, and Mississippi State for processing on the USDA Ginning Laboratory's micro-gin (closely simulating commercial ginning). These samples were used to determine commercial gin turnout, and fiber samples were evaluated at the Agriculture Marketing Service office in Dumas, AR for classer's grade and HVI fiber properties. From this information, premuims and gross returns per acre (based on UDSA loan schedule, which may not accurately reflect differences in final market values) were calculated for each variety.
In addition to yield and fiber quality, relative maturity differences among varieties is an important factor in selecting which varieties to plant. Maturing a crop early is important in avoiding late season insect pressure and insuring that the crop can be harvested before the onset of adverse weather. Planting two or more varieties that differ in time to maturity may be valuable in spreading out equipment requirements. Various measures of crop development were taken at several locations to provide information on relative differences in maturity. At Stoneville, physiological development was monitored from early July until late August by periodically determining nodes above white bloom (NAWB, the number of nodes from the uppermost first position white bloom to the terminal) in ten plants per plot in three replications. A value of 5 or less for NAWB (NAWB5) is considered an indication of imminent cutout and can be used in deciding when to terminate insect control efforts. The number of days from planting to NAWB5 was calculated for each variety.
The number of nodes above the uppermost first position cracked boll (NACB) can be used as an indicator of harvest readiness. A boll is considered mature if it is four or fewer nodes above a boll which has already cracked. When the crop averages four or fewer NACB, it is usually safe to defoliate. NACB counts were made on ten plants per plot in three replications of tests at Stoneville, Sumner, Mississippi State, Brooksville, and Raymond approximately 130 days after planting. At some locations, percentage of bolls open was also determined at that time by counting open and green bolls on five plants in each of three replications.
In addition to the main variety tests discussed above, a separate test comprised of 24 varieties was conducted on narrow (30- or 32- in.) rows at three locations in the Delta, and a test comprised of 31 varieties was conducted with and without a nematicide on a reniform nematode-infested soil near Egremont, MS. The narrow row test in the Delta was planted at Stoneville, Sumner and Percy, with yield and fiber properties determined in the same way as for the main variety tests. At Egremont, five replications were used, the test was planted in a 2 x 1 skip row pattern, and only seed cotton yield was determined.
In all tests, seed of each variety was supplied by the company that submitted the variety for testing. Recommended management practices were followed in each test. The on-farm cooperators decided planting dates, fertilizer rates, amount of supplemental irrigation, defoliation date, insect and weed control strategies, and harvest date. These tests do not encompass all growing and environmental conditions in the state, but they provide a guide to producers in selecting among varieties best suited for their area or growing conditions.
Results from the narrow row test at Percy and the Mid-Season Variety Test at Verona are not reported due to excessive variability in the data. Data tables for other tests are organized as follows:
At the bottom of each table are summary statistics that are very important in interpreting the test results. Despite efforts to provide a uniform test environment, all experiments are subject to a certain degree of error due to variation between plots arising from differences in soil type, fertility, insect damage, weed pressure, etc. Therefore yield potential (and performance with respect to other characteristics) cannot be measured with complete accuracy. By conducting replicated trials we can account for or remove some, but not all, of the effect of non-uniform conditions among plots. As a result, the mean performance of some varieties may be numerically different due to natural variation in the data, but not statistically different when variability in the test is taken into account. The least significant difference (LSD) is a statistic that estimates the smallest difference between two varieties that should be considered something other than natural variation. For example, if the LSD for lint yield in a given trial is 80 lbs/A, varieties that differ by less than 80 lbs/A should be considered equal in yield. In key tables and for key traits, values that are not significantly different from the variety with the highest value (or in the case of NAWB5 and NACB, the lowest value) in the trial are shown in bold type. For example, in Table 1, the highest yielding variety in 1994 was Stoneville 474 with 1237 lbs/A. The LSD for this data set was 75 lbs/A. All varieties yielding within 75 lbs/A of 1237 (i.e. 1162 or greater) are considered equal in yield to Stoneville 474 and are shown in bold type. In some cases, yield data from 1992 for example, data were not available to calculate LSD values and only means are presented. The LSD values given in this bulletin are at the 5% probability level which means that 5% or less of the time, the analysis indicates that two varieties are equal when if fact they may be different. The letters "NS" in place of an LSD value indicate that there was no statistical difference among varieties in that trial for the trait in question.
The coefficient of variation (CV) is a measure of relative precision of a given trial and is generally considered to be an estimate of the amount of unexplained variation in that trial. In general, the higher the CV, the less precise is a given trial.
| Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the Mississippi Agricultural and Forestry Experiment Station and does not imply its approval to the exclusion of other products that also may be suitable. |
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