ABSTRACT

Three experiments at the University of Arizona Maricopa and Marana Agricultural Centers in 2002 and 2003 measured effect of plant populations on the yield of cotton planted in the twin seed-line per bed configuration. In 2002 at the Maricopa Ag. Center, the plant populations were 52800, 69200, 82800 and 96200 plants per acre (PPA) for Stoneville 4892BR and 54800, 70800, 90500 and 104500 PPA for AG3601, respectively. The two lowest plant populations which were in the range of common commercial plant densities resulted in the greatest lint yields for both varieties (an average of 1708 and 1287 lb lint/A for ST4892BR and AG3601, respectively) but there was a significant linear decrease in yield with increasing plant population. In 2003, the cotton variety Delta Pine 449BR was planted and the population densities were 22000, 29000, 36000, 46000, 51000, 61000, and 64,000 PPA at the Marana Ag. Center and 24000, 34000, 41000, 56000, 63000, 71000, and 86,000 PPA at the Maricopa Ag. Center. Cotton yield did not vary significantly as a function of population density at Maricopa and averaged 1526 lb lint/A. At Marana there was a slight trend of increasing yield with increasing plant densities with the three highest plant populations averaging 1385 lb lint/A. In the experiments with ST4892BR and AG3601 at Maricopa in 2002 and with DP449BR in 2003 there was a linear decrease in fiber micronaire with increasing density but this effect of density on micronaire was not observed possibly because plant populations Marana were lower than in the other experiments.