Abstract:
Adequate potassium (K) supply is crucial for cotton growth and development. However, sodium (Na) can share
some functions with K. In present study, we investigated the effects of replacing K with Na at different ratios on growth, ionic relations and yield as well as yield attributes of two cotton varieties differed in K use efficiency. Different levels of K and Na giving K: Na ratios of 3.5: 1 (control), 3.75: 1, 4: 1, 4.25: 1, 4.5: 1, 2.8: 1, 3: 1, 3.2: 1, 3.4: 1, 3.6: 1 were arranged in triplicates according to randomized complete block design under natural field conditions. Results revealed that maximum seed cotton yield was obtained at K: Na ratio of 3.4: 1 followed by 3.6: 1 in both cotton varieties. However, NIBGE-2 manifested greater seed cotton yield than MNH-786. The significant (p≤0.05) positive correlation was found between number of bolls plant-1 and seed cotton yield (R2
= 0.62 for NIBGE-2 and R2 = 0.64 for MNH-786) determined at different levels of K and Na. Leaf K: Na ratio also varied significantly (p≤0.05) due to main effects of K, Na, varieties and their interactions. Maximum leaf K: Na ratio was shown by NIBGE-2 with 270 kg K ha-1+60 kg Na ha-1 at ratio of 4.5: 1 followed by 255 kg K ha-1+60 kg Na ha-1 at ratio of 4.25: 1. Although fiber quality of both cotton varieties were markedly influenced by different ratios of K: Na, however these differences between treatments and varieties were not consistent. There was a significant positive correlation between K concentration and fiber length (R2 = 0.97 for NIBGE-2 and R2 = 0.98 for MNH-786). Our results suggested that cotton growth and yield could be improved by adding appropriate amounts of K and Na.
