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Fluid Journal : Fall 2015
10 The Fluid Journal Fall 2015 ▼ DOWNLOAD were analyzed with K level and cultivar as main factors. For this article, only K levels of 0 and 100.8 kg K ha-1 will be discussed in leaves and reproductive units (squares, flowers, and bolls). Study results Leaves. Regardless of the cultivar or K level, percent of total plant K in leaves increased significantly (p<0.05) at each growth stage throughout the growing season (Table 1). There were no cultivar differences in percent of total plant K Figure 1. Lint yields (kg/ha) of three cotton cultivars, DeltaPine 0912, Phytogen 499, and Stoneville 5458, at two K levels, 0 and 100.8 kg K ha -1. All values are means ± standard error (n=4). Diffferent letters indicate significant differences across all treatments according to Tukey’s HSD test (p<0.05). Table 1. Percent of total K in leaves at four growth stages, pinhead square (PHS), first flower (FF), three weeks after first flower (FF3), and six weeks after first flower (FF6) of cotton plants treated with two K levels, 0 and 100.8 kg K ha-1 . K Level PHS FF FF3 FF6 0kgKha-1 52.15 a 39.6 b 25.99 c 11.18 d 100.8 kgK/ha-1 49.87 a 41.11 b 23.94 c 11.14 d Different letters indicate significant differences among the growth stages within the same K level, according to Tukey’s HSD test (p<0.05). Table 2. Percent of total K in reproductive components at four growth stages, pinhead square (PHS), first flower (FF), three weeks after first flower (FF3), and six weeks after first flower (FF6) of cotton plants treated with two K levels, 0 and 100.8 kg K ha-1 . K Level PHS FF FF3 FF6 0kgKha-1 2.1 d 8.28 c 39.28 b 70.07 a 100.8 kgK/ha-1 3.05 c 7.43 c 38.41 b 60.75 a Different letters indicate significant differences among the growth stages within the same K level, according to Tukey’s HSD test (p<0.05). inleavesatanyKlevel.At0kgKha-1 , PHS had the highest percent of total plant K in leaves with a mean percentage of 52.15 percent, and decreased throughout the growing season with 11.18 percent at FF6. At 100.8 kg K ha-1 , PHS mean percent total plant K in leaves was 49.87 percent and decreased to 11.14 percent at FF6. Reproductive components. Potassium partitioning in reproductive components showed no significant (p<0.05) differences between cultivars at either K levels, however, growth stage showed significant differences (p<0.05) ateachKlevel(Table2).Inthe0kgK ha-1 treatments, FF6 had 70.07 percent of total K in RC, and only 2.1 percent of total K in RC at PHS on average. With 100.8 kg K ha-1 applied, PHS and FF showed no significant differences (p<0.05) and were lower than FF3 and FF6 with 3.05, 7.43, 38.43, and 60.75 percent total K in RC, respectively (Table 2). Lint yield analysis showed significant (p<0.05) differences for the interaction of K level and cultivar (Figure 1). The highest lint yield was found in cultivar DP0912 treated with 100.8 kg K ha-1 with an average of 1565.52 kg lint ha-1 , which was significantly higher than all other treatments. The two lowest yielding treatments were PHY499 100.8 kg K ha-1 and PHY499 0kg K ha-1 treatments, with yields of 1,198 and 1,193 kg lint ha-1 , respectively. DP0912 with 0 kg K ha-1 out- yielded both other cultivars at 0 kg K ha-1 . Conclusions It can be inferred that over the growing season, as boll load increases, K moves from leaves to reproductive components due to an exponential increase in percent of total K in reproductive components and a decrease in percent of K in leaves over time. However, there were no cultivar differences at either K level in either plant part, indicating that these genotypes do not respond differently to low or high K environments. When yield is considered, both low and high K levels on DP0912 and ST5458 out-yielded either K level of PHY499. DP0912 was numerically the highest yielding cultivar at both K levels, and statistically both DP0912 and ST5458 at 0 kg K ha-1 out-yielded PHY499 at 0 kg K ha-1 . These results suggested that DP0912 and ST5458 could be potential cultivars to be planted under low K conditions. Taylor Coomer is an M.S. candidate and graduate research assistant, Dr. Derrick Oosterhuis is a Distinguished Professor with the Department of Crop, Soil, and Environmental Sciences at the University of Arkansas in Fayetteville, and Dr. Leo Espinoza is an Associate Professor and Soil Scientist with the Cooperative Extension Service, University of Arkansas in Little Rock.