Influence of Magnesium and Biostimulant on the Consumption Value and Harmful Nitrogen Compounds Content of Potato Tubers after Storage

The primary use of the potato is direct consumption. The classification of potatoes into consumption type is made on the basis of the consumption evaluation of hydrothermally treated tubers. Nutrient deficiency in the soil, including Mg, contributes to the inhibition of potato growth and development and negatively affects the cooking characteristics of the tubers. Magnesium and biostimulants are responsible for plant nitrogen management. Thus, it is necessary to control the content of harmful nitrates and toxic nitrites in tubers. In potato production, it is also important to maintain appropriate conditions during storage. The purpose of this study was to determine the effect of mineral fertilization with magnesium and a biostimulant preparation during the cultivation of edible potato and long-term storage on the traits determining utility-consumption type and the content of harmful nitrogen compounds in tubers. The study was conducted using the early potato variety Satina. In a three-year (2015–2017) three-factor experiment: evaluation date (immediately after harvest and after six months of storage), soil fertilization with mineral magnesium (0, 30, 60, 90 kg MgO ha −1 ), the application of an amino acid biostimulant (0, 1.5, 3.0 L ha −1 ). Five consumption traits of tubers after cooking, determining the utility-consumption type of potato, were determined. In addition, the consumer safety of the potato was determined based on the nitrate and nitrite content of the tubers. The tendency to overcook tubers significantly depended on all the factors used during potato cultivation. In contrast, the texture and structure of tuber flesh after cooking depended only on mineral fertilization with magnesium. The flesh of the tubers after cooking was most tender (1.0 pt) and firm (1.4 pt) after the application of 60 and 90 kg MgO ha −1 , respectively. The moisture level of the flesh after cooking was significantly influenced by the interaction of magnesium fertilization with the biostimulant preparation. The factors of the experiment did not modify the utility-consumption type (B/A), while there was a change in the type in relation to that specified by the grower—general utility (B). The applied cultivation technology and long-term storage did not deteriorate the consumer safety of tubers (<200 mg kg −1 ) in terms of NO 3 − (max. 112.1 mg kg −1 ) and NO 2 − (max. 1.08 mg kg −1 ) contents. Organoleptic traits: mealiness, moisture, and flesh structure were significantly positively related to the nitrate and nitrite content of tubers immediately after harvesting and to nitrite concentration after long-term storage.