Variety Selection

by Jeffrey C. Silvertooth,
Extension Agronomist - Cotton

When you consider the fact that the survival of a cotton farm depends on yield and quality, it’s not surprising to conclude that variety selection is very important. In the past few years there has been a lot of interest and attention directed towards the cotton varieties that are available to Arizona cotton farmers. Some cotton farmers have questioned whether many varieties available in Arizona are well adapted to this region. In addition, many growers have expressed concern that they have only a limited amount of information available to them regarding variety performance. In the past few years the number and type of varieties available to farmers across the state has increased substantially. Short, medium, or full season varieties are available for cotton producing areas extending from the low deserts to the higher elevation regions. Yield is always an important factor to consider in the selection of a good variety. Farmers also need to consider the fiber properties (length, strength, micronaire, etc.), heat tolerance, leaf hairiness, insect and disease resistance, maturity, and a number of other factors in selecting a variety. Cotton varieties that have been genetically engineered (transgenics) for herbicide tolerance and resistance to insects are also very important to consider when selecting varieties.

There are a number of ways in which a farmer can go about selecting the best varieties to plant on their farm. As with any other decision, the best variety selections are usually based on sound information. Information concerning variety performance can be obtained from a number of sources including seed companies, the University of Arizona Cooperative Extension System, and other local farmers. Variety testing is one of the oldest forms of agricultural experimentation. Even though many aspects of the agricultural industry have changed, variety testing still remains a useful source of information for the selection and management of the best varieties for a region or a specific farm. Variety tests do not have to be elaborate experiments. A good variety testing program should have a few basic features including: a replicated design, representative sites at multiple locations, well managed and realistic growing conditions (good water management and pest control), common ranges in maturity classes among varieties in the test, and at least one variety at each location to serve as a common standard.

The University of Arizona (UA) is involved in a Pima variety development program but does not have an Upland cotton variety development program. Nevertheless, the UA still provides information regarding Upland cotton variety performance from several advanced strain variety tests, and 11 standard Upland commercial variety tests located across the state (Table 1). Seven or eight commercial seed companies commonly participate in the UA Upland commercial variety testing program. These companies market the majority of cottonseed in Arizona. For each of the 11 locations, each of the companies enter two varieties that they feel are best suited for that particular location. Each of the 11 experiments are managed on a county level by the local county Extension agricultural agent, and are located on commercial farms in close cooperation with the farmer. In each case, the individual plots are at least six rows wide (conventional row spacing of 36 to 40 inches), extend the full length of the irrigation run, and are randomized and replicated four times across the field. For example, with seven companies we have 14 varieties, and with four replications, we have 56 individual plots at each location, which can sometimes stretch the patience of even the most cooperative of farmers. Fortunately, we have some excellent farmers that are willing to work with us as cooperators on these projects in an effort to develop information (yield and quality data) that serves to benefit everyone in their areas.

The resultant information from these tests can provide a basis of review for other local farmers as they consider the varieties to plant on their farms in the next season. It can also serve as a comparison with other sources of information on variety performance. However, the best method of measure for many farmers is still a hands-on approach, gained only by trying a variety on their own farm. A grower may tend to plant a dominant (favorite) variety on their farm, but it is always a good idea to diversify the varieties on a farm to some extent each year and to closely observe their growth, development, and yield. Shifting varieties used for different situations, such as soil types or planting dates, is an important part of managing varieties for a farm.

Variety test information is probably most useful in selecting varieties that have both good yield capacities and consistency. In reviewing variety testing data it is not always the variety that comes in at the top of a given test that is the most important, but also the varieties that rank in the top grouping at several representative locations that also deserve careful consideration. This demonstrates the adaptability of a variety across a given region, which contributes to its consistency. All of us are naturally attracted to the varieties that come in at the top of a test, but the varieties that are consistently strong performers are also important to take a look at. This is also very important in terms of variety performance over several seasons. Some varieties may look good for one or two seasons, but not have the capacity to perform consistently over the course of several years, due primarily to variations in weather.

If you are interested in a new and exciting variety for your farm, it would be a good idea to review some of the information available from variety tests. Variety test results are summarized in the UA Cotton Report each year. For example, if you are interested in finding varieties with good heat tolerance, the data from 1994, 1995, and 1996 could be useful. The results from the 1997 entire statewide UA Upland commercial variety testing program are available at this time. Important information for review associated with each test includes not only yield, but also the location, growing conditions, and basic cultural practices. Many of the County Agents are publishing and distributing this information at the county level as soon as it is available. For some tests we also have in-season plant mapping information that can be useful in understanding variety performance.

Full Disclaimers

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona.

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