This experiment in cotton from cv. DPL-50 was held at the Tidewater Agricultural Research and Extension Center, Virginia, USA, in a thick free soil for 3 years. The effect of the foliar applications of K on the cotton yield in the experiment was investigated. Foliar sprays were applied every two to three weeks or starting weekly from the first flowering. The source of K was KNO3 for foliar treatments and KCl was applied to the soil with a recommended dose of 56 kg K2O/ha. KNO3 was pulverized at 2.24; 4.48 and 6.72 kg/ha with a hand held carbon dioxide spray at a rate of 15.3 L/ha. Although foliar treatments at intervals of two to three weeks did not significantly increase yield, a slight increase was observed. The KNO3 applied foliarly at intervals of five to seven days generated a significant increase in the yield of the fiber in comparison with the untreated plots. A 20% increase in fiber yield (196 kg/ha) was observed. The highest fiber yield is associated with the combination in the application of K to soil and foliar, which indicates the importance for the plant of having K available during the development of the cotton acorn. As explained by the author, the doses of KNO3 applied were lower than in the previous trials with potassium nitrate applied foliarly at a dose of 11.2 kg/ha. This may explain the lack of consistent response to foliar treatments in this trial.
Increased yield of cotton lint with foliar applications of potassium nitrate
Abaye, A.O. 1998. Effect of method and time of potassium application on cotton lint yield. Better crops, 82: 25-27