Microagrogenesis of chernozem in agrocenosis

Abstract

The aim of the study was to provide scientifi c and theoretical substantiation for the process of microaggrega- tion of typical chernozem via the simulation of natural processes of soil formation under the effect of systemat- ic application of soil-protecting technologies of crop cultivation with surface packing of root and after-harvest remains, humus, and mineral fertilizers in agrocenoses of the Left-Bank Forest-Steppe of Ukraine. Methods. Laboratory-analytical, experimental fi eld, statistical. Results. During tillage (for over 75 years) the number of free and friable-linked aggregates in the 0–40-cm chernozem layer decreased down to 17–20 %, and on the background of organic-mineral system of fertilization (15 t/ha of humus + N 80 P 75 K 60 ) there was an increase in the content of the mentioned groups of microaggregates up to 20–25 %. The systematic implementation of soil protective technologies promoted the increase in the content of free and friable-linked microaggregates up to 29–32 %. During tillage, the coeffi cient of saturation with humus for physical clay (PC) decreased 1.3–1.4 times compared to the grassland. The value of PC saturation during the soil protective tillage was optimal, as humus was neither accumulated in the form of free humates, nor stored like “fat” in animal organisms.aAnd there was no blocking of nutrients with free humates. Humus acts as a connective tissue, promoting the improved water-resistance of chernozem structure on the micro- and macroaggregate levels. The ability of chernozems to have aggregation was determined by the dispersion factor (DF), which was 12–14 % during tillage without introducing any fertilizers, and 10 % – with the introduction of fertilizers, which testifi ed to a weak degree of microaggregation. With minimal tillage on the background of the organo-mineral system of fertilization, DF = = 6–7 %, and by the end of rotation it decreased down to 3-5 %. Conclusions. Enhanced microaggregation in soil protective technologies is explained by the fact that detritus and newly formed humic substances enhance their role in the formation of organo-mineral complexes in case of optimization of hydrothermal conditions in the seasonal cycle and decreased tempo of humus mineralization. The correlation coeffi cient between the num- ber of microaggregates, sized 0.01–0.25 mm and the content of peptized humic substances during tillage was as follows: R = +0.480.01, and for soil protective technologies it was: R = (+0.70–0.75) 0.01. The increase in microaggregation in conditions of soil protective tillage occurred in the direction of wild land analogs and fallow, which testifi ed to the simulation of the natural process of typical chernozem microaggregation in the agrocenoses of the Left-Bank Forest-Steppe of Ukraine.