Changes in fertility of grey forest soil under systematic use of organic fertilizers in crop rotation

Abstract

The results of researches of organic fertilizers (cattle manure, crop by-products) effect on the agrochemical indicators of grey forest soil have been gained. It was established that in the course of conducting a field experiment, a tendency towards stabilization of the soil solution in the arable soil layer to the level of 5.2, which corresponds to the gradation “weakly acid reaction of the soil solution”, was observed. Hydrolytic acidity for the application of organic fertilizers was at 1.80 mg-ek / 100 g soil. It was affirmed that applying of 30 and 60 tons of manure during the crop rotation cycle on the background of crop by-products resulted in the intensive accumulation of humus in the arable and subsurface layers of the soil 0–40 cm — up to 69.8 and 71.6 t / ha comparing to the control amount of — 48 7 t / ha, while the enrichment of humus with nitrogen stayed at the level of 12.3. Analysis of the humus distribution in the soil profile reveals descending pattern in the lower layers. The implantation of organic fertilizers facilitates the improvement of the nutrient mode of the grey forest soil and growth the amount of hydrolyzed nitrogen up to 15–22%, mobile phosphorus — to 30–57%, exchangeable potassium — to 21–51% comparing to the control (relatively 44.1; 150; 90.8 mg /kg), with no significant migration processes occured. The analysis of the research results shows that the content of hydrolysed nitrogen, both in the control and in the considered fertilizer variants at the end of the rotation, corresponded to an equally low level of supply, while the content of mobile phosphorus was high, with an increase of 34% after the effects of manure and direct action of the straw of the predecessor. A systematic introduction of the by-products of cultivated crops revealed a clear tendency to slightly increase (by 30–40 mg / kg of soil) the content of potassium, which compensates for its constant deficiency in the soil — on average, in the experiment its content varied within the range of 110–130 mg/kg .