Potato Tuber Yield and Quality Under Different Potassium Application Rates and Forms in West Siberia

Potato cultivars have different strategies for dealing with potassium (K) deficiency in soil, and their response to different forms and rates of K fertilisation may vary because of differences in soil K availability. This study was performed to evaluate the effect of K fertilisation rates (0, 30, 60, 90, 120 and 150 kg K/ha) on tuber yield and quality (dry matter, starch, sugar and ascorbic acid content, taste) of two potato cultivars (Roco and Rosara) grown in the microplot field experiment on Luvisol in the forest-steppe zone in southern West Siberia, Russia (NL 54.422106, EL 83.160257). The tuber yield of both potato cultivars increased with increase in K application rate up to 2.1 and 2.9 kg/m² for Roco and Rosara, respectively. Sugar content, averaging 3.5%, was mostly determined by cultivar; however, in both cultivars it tended to decrease with increasing K application rate. The application of K fertiliser in the form of sulphate as compared to chloride increased dry matter content from 22.4 to 23.8% and ascorbic acid content from 13.2 to 14.6 mg/100 g fresh mass. Starch content of potato tubers averaged 59.7 ± 4.8% over all K fertilisation variants, with cultivar responses being different. Potassium application rate did not affect Roco tubers’ taste, while improving Rosara tubers’ taste under moderate application rates. The results underscore the importance to adjust fertiliser recommendations concerning potassium application rates and source on the basis of biological requirements and intended utilization of individual potato cultivars