Bt cotton hybrids may require additional supply of fertilizers, due to increased fruit retention in these crops. In 2006, field experiments with various soil applied N, P and K fertilizer combinations, applied according to local practices, were tested in combination with 4 foliar sprays of 2% potassium nitrate, on 18 locations, in 5 districts in Punjab, northern India. Foliar sprays were applied at weekly intervals, starting from flower initiation.
This study showed cotton yield increases of 11% with foliar potassium nitrate sprays (Figure 1), which resulted in a net increased farmer’s income. This yield increase was found to be irrespective of the soil K status and addition of K fertilizer through soil application. Deducting the costs of the foliar fertilizer product from the gross income, resulted in a benefit to cost (B:C) ratio of over 10,4 to 1.
Figure 1. Average effect of soil K and foliar K application in cotton.