BIOCHEMICAL INDICATORS AND NITRATES IN POTATOES DURING STORAGE: MODERN CULTIVATION TECHNIQUES

It featured the dynamics of the biochemical parameters of potato tubers in the autumn and winter storage peri- od. The samples were gathered in 2011–2013 during field experiments. The experiments included 12 various doses and ratios of mineral fertilizers under drip irrigation. The soil was leached chernozem (Voronezh region). During 3 storage periods (Sep- tember–April), the content of vitamin C in moderately fertilized tubers decreased by 3.0–3.2 times. The content of vitamin C in heavily fertilized tubers decreased by 3.3–3.4 times. The loss of dry matter and starch at small and moderate doses of fertilizers N30-60P90-120K60-90 amounted to 1.4–1.5 and 1.0–1.1%. The loss of dry matter and starch from high doses of fertilizers N120-150P180-210K150-180 equaled 1.6–2.0 and 1.4–1.7%. The content of nitrates in the tubers gradually decreased during stor- age, and the greatest decrease occurred in April. For moderately fertilized tubers, the residual amount decreased by 3.2–3.3 times by April. For heavily fertilized tubers, it decreased by 2.5–2.9 times against 3.7 times in the control sample. Enhanced nitrogen and nitrogen-potassium fertilizer worsened all the biochemical indicators of the potatoes. In order to maintain optimal biochemical pa- rameters of tubers during storage, the proportion of phosphorus (kg/ha of active substance) had to be increased by 1.5–1.7 times as related to nitrogen. The share of potassium was increased by 1.3 times. The best results (yield = 37.8 t/ha, optimal biochemical pa- rameters, concentration of nitrates = 36.6 mg/%) were achieved by drip irrigation and application of N90P150K120 kg/ha of active ingredient. A dose of N120P180K150, (yield – 41.5 t/ha) was found beneficial, provided the potatoes were filled separately from the total pile. Such potatoes have to be sold at the end of the storage period, when the concentration of nitrates in tubers becomes 2.5– 2.9 times lower.