RATIONAL APPLICATION OF MINERAL FERTILIZERS AS THE FACTOR OF ECOLOGICAL SAFETY OF AGROCENOSIS
In a modern agriculture the leading role in increase of arable land efficiency belongs to mineral fertilizers which at minimum expenses give the maximum effect with positive economic benefit. However irrational application of mineral fertilizers can result not only in crop decrease, but also in deterioration of ecological conditions of agrocenosis. Stationary experience was begun in 1995 on low-powered, heavy-leached black earth, with typical for Western Siberia characteristics and properties. The research was carried out at a grain fallow. Calculation of doses of fertilizers on the planned yield of spring wheat, 4.0, 5.0 and 6.0 t/ha has been made annually by an elemental balance. The average dose of fertilizers over years of research, respectively amounted N <sub>125</sub>P <sub>35</sub>; N <sub>200</sub>P <sub>65</sub>; N <sub>270</sub>P <sub>115</sub> kg of active ingredient per hectare. The fertilizers were applied before sowing under sowing cultivation. As a result (if a long-term research it has been established, that in a forest-steppe zone of the Urals the probability of 3.0 t/hectares productivity of spring wheat makes 100 %; 4.0 t/hectares makes 76 %, that is reasonable for economy. The yield of 5.0 and 6.0 t/hectares decreases to 45 % and 9 % accordingly. Application of mineral fertilizers on a planned productivity 6.0 t/hectares of spring wheat leads to migration of nitrates to the depth of 80 cm at the first half of vegetation. At a lower level of a mineral feeding the nitrates remain in the layer 0-50 cm. Out of 270 kg of nitrogen introduced at the end of vegetation period, 22 kg (8 % of a dose) is found at the layer of 80-100 cm and this can cause pollution of subsoil waters.