Symposium Introduction

Soil - the top layer of land, under the influence of plants, animals, microorganisms and climate of the parent rocks, on which he located. This is an important and complex component of the biosphere, is closely associated with other its parts.

Under normal conditions, all the natural processes occurring in the soil, are in equilibrium. But often in violation of the equilibrium state of the soil responsible person. As a result of human economic activity contamination occurs, change the composition of the soil, and even its destruction. The fertile soil is formed very long time. At the same time every year, together with the harvest from the soil removed tens of millions of tons of nitrogen, potassium and phosphorus -- main components of plant nutrition. The main factor of soil fertility -- humus (humus) is contained in the black soil in an amount less than 5% of the mass topsoil. On poor soils, humus, even less. Without replenishment of soil nitrogen compounds, its stock could be depleted in 50 -- 100. This does not happen, since farming provides Spreading organic and inorganic (mineral) fertilizers.

Soil nitrogen fertilizers are used by plants by 40-50%. Rest part (about 20%) recovered microorganisms to gaseous substances -- N ₂ , N ₂ O - and disappears in the atmosphere or washed out soil. Thus, the mineral nitrogen fertilizers do not have long action and therefore they have to pay annually. Adverse changes soil occur as a result of improper rotations, ie annual planting the same crops such as potatoes. Inclusion in the same rotation legumes enrich the soil with nitrogen. Clover and alfalfa at the expense binding N ₂ symbiotic rhizobia can hold in the soil up to 300 kg of nitrogen per 1 hectare. Rotations are needed for the fight with herbivorous nematode worms, which significantly reduces yield. For example, onion-garlic nematodes can reduce onion harvest 50%.