The monograph contains general information about the occurrence of allelopathic soil sickness under cultivated flowers, crops and fruits. It also discusses (a) the ancient (b) methods to control soil sickness, (c) chemical nature of substances exerting the toxic effects, (d) the role of microorganisms, (e) physiological and biochemical processes of individual organisms of soil sickness. It also describes the methods and possible ways to overcome this phenomenon. The publication is intended for specialists in the field of plant physiology and biochemistry, geobotany, soil science and agricultural, in the field of agriculture and crop production, as well as for instructors and students.