Effect of source and level of potash on yield and quality of potato tubers

Field experiments were conducted for two consecutive seasons at NARC potato research area Islamabad, Pakistan, to study comparative effect of source, levels and methods of K fertilization on yield and quality of potato produce. Nitrogen and phosphorus were applied at 250 and 125 kg ha/sup -1/, respectively whereas three K/sub 2/O levels, 0, 150 and 225 kg ha/sup -1/ from two sources of potash (SOP and MOP) were tested. Potassium was also applied as foliar spray at 1% K/sub 2/O solution at 30, 45 and 60 days after germination (DAG) and soil was also amended by 150 kg K/sub 2/O ha/sup -1/. A significant increase in tuber yield with K application at 150 kg ha/sup -1/ as K/sub 2/O from both the K sources over NP treatment was recorded. Increase in tuber yield with K/sub 2/O at the rate of 225 kg ha/sup -1/ was statistically nonsignificant compared to 150 kg K/sub 2/O ha/sup -1/. A positive interaction between soil applied P and K with N in plant system was observed. Potassium treatments not only increased K concentration but also affected N and P contents in potato tubers. The quality parameters like dry matter, specific gravity, starch contents, vitamin-C and ash contents were also affected with P and K fertilization. (author)