Effect of Mineral and Bio NPK Fertilizers and Foliar Spray with Some Growth Stimulants on Growth and Productivity of Potato

Potato is highly responsive to NPK fertilizer, chemical fertilizers have several negative impacts on environment and sustainable agriculture. Therefore, two field experiments were carried out during the two successive summer seasons of 2018 and 2019 at the experimental farm of the Faculty of Agriculture, Moshtohor, Benha University to investigate the effect of different levels of mineral NPK fertilizers added with bio fertilizer to the soil (F₁, 100% mineral NPK fertilizer (as recommended dose); F₂. 80% mineral NPK fertilizer + Bio fertilizer and F₃, 60% mineral NPK fertilizer + Bio fertilizer)  and foliar spray with growth stimulant such as Potassium citrate at 5g/L, Yeast extract at 5%, Seaweed extract at 5%,  Garlic extract at 5% and Control (without spraying) as well as their interaction on vegetative growth characters, chemical constituents of plant foliage, total tuber yield, physical and chemical quality of potato tubers (Solanum tuberosum L.) cv. Sponta. Results indicate that applying the treatment 80% RDF+ biofertilizer followed by treatment 100% RDF without bio fertilizer reflected significantly and the highest values in all measured vegetative growth aspects (plant height, No. of branches, No. of leaves, total fresh and dry weight/plant); chemical constituent of N, P, K and carbohydrate percentage; total produced tuber yield and its components expressed as total yield/plant, total yield/fed, average tuber weight, tuber length and tuber diameter; and  chemical tuber quality expressed as content of N, P, K, total protein, total Stretch and NO₃ of potato plants compared with 60% NPK fertilization at the recommended dose of mineral fertilizer which gave the lowest values in the two seasons of study. In this regard, spraying the plants with yeast extracts at 5% or seaweed extract at 5 ml/l gave the significant highest values of all studied characteristics of potato plants in both seasons. Results also indicate that fertilizing potato plants with 80% RDNPK added with bio fertilizer combined with either yeast extracts at 5% or seaweed extract at 5 ml/l spraying every 10 days during the growth season gave the highest values in all studied characteristics.