Potato yield and tuber quality as affected by gibberellic acid and zinc sulfate

Abstract Obtaining high potato (Solanum tuberosum L.) tuber yield through increased number and weight of quality tubers is important for farmers while the quality factors are of interest for food processing industries. Potato processing industries require high quality tubers having the highest possible dry matter, starch and protein contents. A twoyear field study was carried out as a factorial experiment in a randomized complete block design during 2013 and 2014.  Gibberellic acid (GA3 at 0, 100, 200 and 400 mg·L1 levels) and zinc sulfate (at 0, 500, 1000 and 2000 mg·L1 levels) were foliar sprayed on potato plants 20 and 50 days after tuber sprouting, respectively. There was no significant difference in all measured criteria between two years of experiment. Comparing to control, a 38% increase in total tuber yield resulted from treatment with 200 mg·L1 GA3 and 1000 mg·L1 zinc sulfate. The greatest tuber dry matter content (24.33 g·100g1 fw) obtained from 200 mg·L1 GA3 plus 2000 mg·L1 zinc sulfate treatment, while the highest starch contents (32.56 % tuber fresh weight) was obtained from sole application of zinc sulfate at 2000 mg·L1.Application of GA3 at 400 mg·L1 and zinc sulfate at 2000 mg·L1resulted the highest tuber crude protein content of 8.37% tuber dry weight which was over twice as control treatment.  Manipulating plant nutrition and fertilization could be used as a powerful tool to obtain desired quality and quantity of potato tuber.