Pylypchenko A. Agrobiological aspects of hemp (Cannabis sativa L.) cultivation by organic farming system under the unstable moisture conditions of Ukrainian forest-steppe

The dissertation is devoted to an important agricultural problem - introduction of organic technologies on the example of a universal and highly demanded crop - hemp (Cannabis sativa L.). The modern literary sources on the subject of the experiment were analyzed, the influence of organic technologies on agrochemical and agrobiological properties of the soil was studied. The role of varieties and growing conditions on formation of yield and quality of hemp products was determined. Modern hemp varieties were used in the experiments, among which were varieties developed with the direct participation of the author. The research was carried out using modern agricultural techniques and technologies, which were developed and tested under the author’s supervision. It was found that application of biological destructor Biostimix-Niva with a rate of 1 l/ha increases the the amount of biomass in the soil by 3.2-3.6 t/ha, labile soil substances by 1.1-1.4 t/ha and organic carbon by 3.2-5.4 %, but did not affect the macroelements content in the soil. Organic cultivation technologies contributed to an increase in the content of alkaline-hydralized nitrogen almost by 3 mg/kg. The application of biological destructor Biostimix-Niva can be characterized by some decrease in the intensity of root mass growth and yield decrease, which have a correlation with each other - r = 0.50. However, this does not have a negative impact on the economic parameters of hemp cultivation. The P2O5 content on the variants with pasture, fallow and transitional crops of corn and hemp was 16.6 mg/kg lower compared to the variants grown by organic technology. The average K2O content was 83.6 mg/kg on the inorganic variants and 100.1 mg/kg on the organic ones. The application of organic technology improved the agrobiological properties of the soil - the intensity of tissue destruction was observed on the variants grown by organic technology - 30.5 %, on the variants with transitional technology - 28 %. Organic farming techniques increase the number of microorganisms in the soil, but they also increase the number of pathogens. An important influence on the condition of soil bioindicators was revealed - during the research years the number of earthworms on the variants with pasture and inorganic cultivation technologies was 6-10 individuals/m2 lower compared to the organic technologies, and the difference in rotifers and nematodes was 4-5 and 20-21 individuals respectively. The components of soil biota were proved to be in a system of correlations with each other. Microorganisms accumulating nitrogen and phosphorus have a strong correlation with the fungal component of the biota (r = 0.72-0.89), so this feature must be considered and studied in the case of using organic growing technologies. It was found that the proportion of variety influence on biometric indicators and the yield of hemp straw and fibre was 62-95%. The influence of cultivation technology was only 8 %, but under organic cultivation it is an important factor in managing the yields of hemp seed. The yields of seed were independent of soil fertility, depending on the variety by 66 % and on the growing conditions of the years of cultivation by 12 %. The most important biometric characteristics of hemp plants are plant height and root system mass gain. One of the most promising varieties is the variety Lara, which provided a fibre yield of 3.50-3.68 t/ha. Cultivation of hemp using organic methods increased the yield of fibre by 0.05 t/ha on average. The highest yield was recorded for the variety Sula, which exceeded 0.6 t/ha. The varieties Hloba, Zolotoniski 15, Lara and Sula were found to be suitable for dual cultivation for seed and fibre. The variety Hliana is only suitable for fibre cultivation. The fibre content of the hemp stalks was independent of the cultivation technology, which supports a focus on growing the crop according to the principles of organic farming. The main factor that form this indicator is the variety properties. A direct correlation (r = 0.35) was found between oil content and fiber content in the experiment, while for the varieties Hloba and Sula it was inverse: -0.43 and -0.40, which proves the need for careful selection of varieties for cultivation. The importance of organic cultivation technologies lies in their indirect effect on soil biomass and labile humus content, which have high correlation coefficients with oil content. Cultivation of hemp using organic technology is definitely cost-effective. The cost of seed for both technologies is the same and amounts to 3,000 UAH/ha. The yields of seed range from 0.51 to 0.74 tonnes per hectare. The yield of hemp straw is 3.7 to 4.4 tonnes per hectare. Profitability ranges from 15.3% on the control and 23.0; 38.6 and 78.9% respectively on the variants.