The number of cotton varieties needed to account for a major portion of the U.S. acreage has increased. In 1972, two varieties, Stoneville 213 and Deltapine 16, accounted for 50% of the U.S. acreage. Stoneville and Deltapine varieties accounted for 43% of the U.S. acreage in 1986 but this acreage was divided among 13 Deltapine and six Stoneville varieties. The five most popular varieties in 1986 accounted for only 37% of the U.S. acreage.

Varieties earlier in maturity than Deltapine 16 and Stoneville 213 became readily available for planting in the late 1970's and the planting percentage of these two varieties rapidly declined. The percentage of early maturing varieties increased significantly from 1978, to 1986 in the Mid-South and Texas. In 1978 early maturing varieties accounted for only 15, 8, 17, 13, 25, and 22%, respectively of the Mississippi, Arkansas, Tennessee, Missouri, Louisiana and Alabama acreage but this increased to 94, 98, 99, 92, 78 and 76%, respectively, for the same states in 1986. In contrast, only small increases in the percentage of early maturing varieties occurred in the southeast and western cotton growing regions during the same period.

Regression coefficients were calculated for the number of days from planting to final harvest in cotton variety tests at four locations. These regression coefficients showed that the number of days from planting to final harvest decreased at the rate of 1.18, 2.49, 1.33, and 2.43 days/year for Stoneville and Sumner, MS; College Station, TX; and Florence, SC respectively.