EFFECT OF CRUDE OIL CONTAMINATION ON SPRING RAPE VULNERABILITY BYDOWNY MILDEW IN FOREST GRAY SOIL
The work is devoted to the assessment of the impact of a single oil pollution of the soil on the yield and disease incidence of spring rape plants (Brassica napus L.). The study was conducted in experimental site of agrochemistry and soil science department of Kazan State Agrarian University, which is located in Predkamye zone of Tatarstan Republic. The soil in experimental site is clay loamy gray forest soil, which is typical for this zone. The main nutrient properties of uncontaminated soil was low content of humus, slightly high content of labile Phosphorous and moderate availability of labile Potassium, the pH was slightly acid. The soil was intentionally contaminated by crude oil on soil surface at the rates of 10, 20 and 40 l/m2. Based on the previous research, the contamination levels in this study are presented as low, moderate and high levels. The yield of oilseeds of spring rape was closely correlated with the level of one-time pollution of gray forest soil with crude oil over at least 15 years. The results showed that the increase of downy mildew abundance (R2=0,8804) and development(R2=0,8610) correlated with the soil contamination level. Consequently, both abundance and development of downy mildew induced asignificant negative effect on the yield of the main and side rape production. The strength of oil seeds production correlation with the level of plant infection (R2=0,8652÷0,8759) was more significant as compared to the correlation strength with the decrease of rape shoot yield (R2=0,8013÷0,8192)