Enhancing potato growth and quality through macronutrient and zinc fertilization: a field-based study on osmolyte responses and quality trait

Macronutrients regulate each aspect of plant function, including metabolism, resource allocation, growth, and development. Zinc (Zn) is a vital micronutrient essential for optimal growth and enhanced quality of potatoes. A field trial was performed to study the impacts of different levels of NPK and Zn fertilization on potato farming. Various levels of NPK (low, medium, and high) with the ratio of 2:1:3, and different levels of Zn were applied (0, 15, 30, 45 and 60 kg ha−1) in soil. The findings revealed that different doses of NPK and Zn fertilizers not only affect growth patterns and yields but also augment potato quality by modulating reducing sugars by 40.95%, starch content by 79.29%, sucrose enzyme activity by 42.19%, glutamine synthetase by 82.10%, and sucrose phosphate synthase by 45.47% compared to no use of Zn and low levels of NPK. It was evident that all quality and production indices improved at low to medium NPK fertilization levels, thereafter decreasing at increased NPK and Zn fertilization levels. In contrast, the phosphorous contents in the tuber and soil showed antagonistic effect with the increasing rate of Zn in the soil rhizosphere. The concentration and absorption of Zn and NPK in the soil–plant continuum were particularly influenced by the experimental treatments. Additionally, a significantly strong correlation between the balanced use of fertilization with tuber carbohydrate and protein was identified. Therefore, it is recommended that a combined use of synthetic fertilizers (NPK) and Zn, with a dosage of 150–75–225 kg ha−1 (NPK) + 30 kg ha−1 of Zn, be applied to potato crops in order to achieve optimal growth and maximize crop yield.