Influence of Source and Time of Potassium Application on Potato Growth,Yield, Economics and Crisp Quality

Field studies were conducted at the Central Potato Research Institute Campus, Modipuram (India), during two seasons (2003–2004 and 2004–2005), with two processing cultivars (cvs Kufri Chipsona-1 and Kufri Chipsona-2) and nine combinations of potassium source (K-chloride, K-sulphate and K-nitrate) and time of K application (basal dressing, split application and split application + foliar spray) to investigate their effect on tuber yield and processing attributes for crisp production under subtropical conditions. Yearly variations were observed for most of the variables studied. Between cultivars, the tuber and biomass yield was higher in cv. Kufri Chipsona-1, whereas specific gravity, tuber dry-matter percentage and crisp recovery were higher in cv. Kufri Chipsona-2. Stem number, plant height and compound leaf number were not influenced by sources of K fertilizer or application time. Processing-grade tuber yield, total tuber yield and biomass yield were statistically similar for K-chloride and K-sulphate and lower for K-nitrate. K sources affected both specific gravity and tuber dry-matter percentage significantly; K-sulphate and K-nitrate gave significantly higher values than K-chloride. The application time had no significant effect on processing grade and total tuber yield or on tuber specific gravity and dry-matter percentage. Values for crisp colour and reducing sugars were within the acceptable range for all treatments. Crisp yields were calculated to be highest and oil percentage of the crisps to be lowest when K-sulphate was applied as K fertilizer. Net income and benefit:cost ratio were highest for K-chloride followed by K-sulphate and lowest for K-nitrate. The study suggests that for crisping potatoes, K-sulphate is more suited than K-chloride, as it not only increased tuber dry-matter percentage and crisp yield, but also decreased crisp oil percentage.