This experiment in cotton cv. DPL-50 was conducted at the Tidewater Agricultural Research and Extension Center, Virginia, USA on a coarse-loamy soil for 3 years. In one experiment the effect of foliar K applications on cotton yield was investigated. Foliar sprays were applied every two/three weeks or weekly starting from first bloom. KNO3 was the K source for foliar treatments and KCl was applied to the soil at the recommended rate of 56 kg K2O/ha. KNO3 was sprayed at 2,24, 4,48 and 6,72 kg/ha with a carbon dioxide hand-driven sprayer at a rate of 15,3 L/ha. Even though foliar treatments at two to three weeks interval did not increase yield significantly, a slight increase was observed. Foliar KNO3 applied at five to seven days interval resulted in significant lint yield increase compared to the untreated plots. A 20% increase in lint yield was observed (196 kg/ha). The higher lint yield for a combination of soil and foliar applied K indicates the importance of plant available K during cotton boll development. As the author explained, the KNO3 rates applied were lower than in previous trials with foliar-applied potassium nitrate at a rate of 11,2 kg/ha. This can explain a lack of consistent response to foliar treatments in this trial.
Abaye, A.O. 1998. Effect of method and time of potassium application on cotton lint yield. Better crops, 82: 25-27.