THE AUTHORS

Bobby Phipps, Assistant Professor in Agronomy and State Extension Cotton Specialist; Andrea Phillips, Research Specialist; and Bobby Tanner, Farm Worker.

ACKNOWLEDGEMENT

A special thanks goes out to our producers/cooperators Charles Parker, Johnny Hux, and Chuck Provance for the use of their natural resources which allows the Missouri cotton producers a reliable and unbiased source of information.

COMPARING VARIETIES

The performance of a variety cannot be measured with absolute precision. Uncontrollable variability influences the yield of each variety. One source of variability often found is the soil not being uniform throughout the test site (location). There are other factors that contribute to this variability. Some of the variables are uncontrollable due to economic and technical reasons. Statistical analysis is used to evaluate and make comparisons on what is being studied (yield), and at the same time measuring and evaluating the uncontrollable variables. Duncan's multiple range test was used to compare all variety yields to each other. Varieties that are followed by the same letter are not statistically different from one another at .05% level. This means if two yields are followed by different letters, then the higher yielding variety has a 95% chance of being superior to the lower yielding variety. A measurement of the uncontrollable variables is C.V. (Coefficient of Variation). As the C.V. increases, the amount of uncontrollable variables are increasing and influencing the test results.

COTTON VARIETY PERFORMANCE TRIALS

Cotton variety trials are carried out as part of the Cotton Project of the University of Missouri Agricultural Experiment Station located at the U.M.C. Delta Center. These tests are conducted to provide a reliable, unbiased, up-to-date source of information for comparing varieties. The Roundup Ready trial had an application of Roundup applied over the top before five leaves appeared and one directed spray application later in the growing season.