Potato responsiveness to fertilizers and crop losses from late blight in the North-West of Russia

Late blight is one of the most harmful potato diseases in the North-West of Russia. Today, its negative effects are aggravated by weather and climate changes. The goal of a comprehensive study carried out in the Menkovsky branch of the Agrophysical Institute in 2012–2017 was an assessment of the harmfulness of the late blight pathogen depending on soil-agrochemical, weather and climate conditions. The methodical basis of the research was a prolonged field agrophysical stationary experiment in the system of field and vegetable-feed crop rotations, where potato was cultivated after winter rye and after barley, which, in turn, were grown after perennial grasses. The objects of the study were potato ‘Lomonosovsky’, sod-podzolic soil with different degree of cultivation and fertilizer systems for the culture. Potato ‘Lomonosovsky’ is early ripening variety, its tubers are medium resistant to the late blight agent, and its tops are weakly resistant to it. The sod-podzolic soil had average, good and high cultivation degree. Sandy loam soil in the experiment had the value of pHKCl of 5.2–6.3, the humus content of 2.1–3.7%, the content of mobile P2O5 and K2O compounds of 195–676, 97–298 mg/kg, respectively. In well- and highly cultivated soils, these parameters were maintained by the application of 35 and 70 t/ha of organic fertilizers for potato, respectively. The experimental factors were the degree of soil cultivation (average, good and high) and the level of mineral fertilizer application for a given efficiency of photosynthetically active radiation (PAR efficiency of 1–3%, without fertilizers; PAR efficiency of 2–4%, N80P20K100; PAR efficiency of 3–5%, N120P30K150). In the course of the comprehensive study, the parameters of potato damage by late blight and the level of crop losses were established depending on the agro-climatic soil-agrochemical conditions. Agronomic efficiency of the studied variants of the fertilizer system for potato was high. The level of tuber yield increase and payback of 1 kg of fertilizers’ active substances reached 33–58% and 8.3–11.6 cereal units (CU) for the mineral system, 25–45% and 3.9–8.0 CU for the organic one, and 33–79% and 3.8–6.7 CU for the organic and mineral fertilizer system. Under non-epiphytotic conditions (2 of 3 years of the observation), against the background of low and moderate damage rates, the total yield loss was 5%, and the soil improvement and organic and mineral fertilizer application reduced them by 30–80%. Against an epiphytotic background, repeated 1 time in 3 years, the damage of tops and potato tubers increases by a factor of 4.3 and 6.1, the intensity of the damage grew 2.8 and 3 times, and the development increases by a factor of 12 and 17.5 times, respectively. In the epiphytotic years, yield losses increased 5.2 times (up to 26%), and the mineral fertilizer system reduced them only in medium cultured soil. Against this background, increasing the soil cultivation degree and organic fertilizer doses to a high level is ineffective.

Key words: potato, organic fertilizer, mineral fertilizer, late blight, damage, epiphytoty, yield, yield loss