Marketable potato yield was significantly affected by K application (Fig. 1) as more
marketable potatoes were produced form K treated plots as compared to NP and N alone
treatments. Application of K2O at 150 kg ha-1 enhanced the marketable potato tuber yield
significantly; the increase in yield was more with MOP as compared to SOP. The
difference between marketable potato yields at different K levels was non-significant;
yield increase was only 6% from applied at 225 kg K2O ha-1 over that of 150 kg K2O ha-1
treatment for SOP, while it was only 4% for MOP source. This gave clue about the
economics of the K fertilizer use in terms of return in yield (kg) per unit use of K
fertilizer. Superimposed foliar application of K increased tuber yield significantly
(12.7%) over that of soil applied K at 150 kg K2O ha-1. However, it is necessary to apply
K through foliar spray in the concentration of salt to be kept as low as on safer side to
cause phyto-toxicity. In the present study, salt concentration was 1 % only, so it was on
safer side to cause the phyto-toxicity and it improved the plant vigor instead of harming
plants. Langhlin (1962) used successfully K2SO4 spray at up to 10%, while KCl solution
above 4% caused leaf damage.