IMPROVING YIELD AND QUALITY OF SOME NEW POTATO VARIETIES IN WINTER PLANTATION USING ORGANIC STIMULATORS

Field experiments were carried out at El-Baramoon Research Station, Mansoura, Dakahlia Governorate, Egypt (+ 7m altitude, 30 11 latitude and 28 26 longitude), during winter seasons of 2007/08 and 2008/09, to study the use of various biostimulants, i.e., humic acid (3 ml l), seaweed extract (4 g l) and amino acids (5 ml l) and/or 50% of recommended NPK fertilizers as well as control (100% NPK) on some new potato cultivars (Alaska, Fridor and Oceania) and Spunta when cultivation in low temperature in order to prolong the export season, which are equivalent free radicals in cells and plant tissue leading eventually to further stimulate with potato plants to low temperature conditions (cold stress), and improved the productivity, yield quality and superoxide dismutase SOD activity. Research also aimed to reduce reliance on chemical fertilizers. The obtained results revealed that potato cultivars differed significantly in all studied characters. Spunta cv. had more fresh and dry weights per plant, leaf area, tuber yield and yield components, nitrate content and SOD activity, followed by Oceania cv. , in both seasons. On the other hand, Fridor and Oceania cvs had significant higher dry matter, specific gravity, NK-uptake, and starch content than other two cvs. There were insignificant differences among cvs in P-uptake and nitrite content. Meanwhile, Alaska cv. gave the highest reducing sugars in comparison with other cvs. Application of seaweed as foliar spray + 50% of recommended NPK gave rise to a significant increase in most of the studied characters, i.e., fresh weight, dry weight, leaf area, total tuber yield, number of tuber per plot, average tuber weight and tuber weight > 50 mm, in both seasons. Moreover, foliar application of humic acid or seaweed extract plus NPK 50% significantly increased tuber quality, i.e., tuber dry matter, specific gravity and starch content and reduced significantly reducing sugars, in two seasons of study. Meanwhile, NPK-content (both seasons) and SOD (1 season) was significantly increased when potato plants treated with humic acid + NPK 50%. On the other hand, addition of organic stimulators plus 50% NPK significantly decreased NO3 and NO2 content in potato tubers, compared with full or half dose application of NPK at both seasons of study. The interaction between potato cvs and application of organic stimulators plus inorganic fertilizers had significant effects on all characters in both seasons of this study. The most effective treatments were Spunta cv. x SW + NPK50% and Fridor cv. x HA + NPK50%. This study suggests that seaweed extract or humic acid as foliar application plus half dose of recommended NPK on potato plants in the winter season are the most effective treatments for high productivity and quality associated with integrating organic stimulators and inorganic fertilizers, which represents an environmentally and agronomically sound management strategy. Also our results indicate that increased SOD activity due to application of stimulants improved physiological health, protected plants against cold stress, reduced stander fertilizer, while maintaining adequate growth and productivity of potatoes.