The spread of rhizoctoniosis in potato plantings in the conditions of the North-West of the Russian Federation with a heterogeneous content of nutrients in the soil

Rhizoctoniosis is one of the most common and harmful diseases of potatoes in the North-West of Russia. The degree of its manifestation depends on many factors, including the content of basic nutrients in the soil. In the Leningrad region the effect of prolonged application of organic and mineral fertilizers on the degree and nature of the manifestation of rhizoctoniosis was studied in potato variety Meteor in forage and field crop rotations. By the results of the detailed accounting carried out in 2022 including observation of all potato plantings (43406 in total) it was determined that rhizoctoniosis damage had random distribution character in field crop rotation and focal distribution in forage crop rotation. This conclusion was confirmed by respective coefficients of variation (79 and 87 %) and aggregation (1.0 and 1.5). Spatial heterogeneity of plants damaged by rhizoctoniosis was visualized on digital maps compiled with GIS AFI and Surfer 11 while grouping the data into elementary sections. There was sufficient influence of cultivation and fertilization of different levels on rhizoctoniosis spread. The influence of cultivation was weak and statistically significant only in forage crop rotation, where there was an increase of rhizoctoniosis damage of potato plants (by 1.7-2.5 times compared to low cultivated soil). Under mineral fertilizers application there was a decrease of rhizoctoniosis damage of potato plants both in field crop rotation (by 1.1-1.7 times compared to variant without fertilizers application), and in forage crop rotation (by 1.1-1.3 times). Complex influence of soil cultivation and fertilization of potato plantings caused a decrease of rhizoctoniosis damage of potato tubers by 1.9 and 2.0 times in field and forage crop rotations, respectively.