Biological and agrochemical properties of the meadow-chernozem soil of Omsk Irtysh region and fodder crop productivity as influenced by mineral fertilizers

The world experience indicates that both natural factors (soil fertility, plant biopotential, etc.) and agrogenic effects (fertilizers, farming systems, etc.) promote sustainable growing crops. Mineral fertilizers have an impact on the abundance, activity and diversity of soil microflora by increasing the productivity of the system, the return of plant residues and the content of organic matter in the soil. Here we show that as a result of the systematic application of mineral fertilizers, the biological state of meadow-chernozem soil remains favorable for a number of microbiological indicators and for an increase in fodder crop yields. Our purpose was to assess the effects and relationship of application of fertilizers on soil microbiological and agrochemical parameters and, as a result, on crop productivity. The tests were carried out in 2020-2022 in the forest-steppe zone of the South Western Siberia, Omsk region (55.04192°N, 73.46504°E) in a stationary field experiment. The content of mobile phosphorus in the soil according to Chirikov is medium. In eight-field grain-grass crop rotation, a mix of perennial grases Dáctylis glomeráta L. with Onobrýchis arenária (Kit.) DC. and annual sorghum-sudank hybrid grass Sorghum ½ drummondii (Steud.) Millsp. & Chase were grown. The number of different physiological groups of microorganisms, enzymatic activity, the content of nitrates, the nitrification ability of the arable soil layer, and crop yields were assessed. We revealed that the growth of agronomically valuable groups under annual grasses is more intensive than under perennial grasses. Optimized mineral nutrition (N60P60) of the mixed grass stand stimulated mostly the growth of the phosphate-mobilizing microorganisms and soil micromycetes (by 118 and 122 % compared to control), under the sorghum Sudangrass hybrid, the number of amylolytic and oligonitrophilic microbiota significantly increased by 57-90 % vs. control, respectively. The analysis of changes in the total microbial number showed the stimulating effect of mineral fertilizers on the soil microbocenosis under agricultural crops. The use of mineral fertilizers affected the total microbial numbers equally under perennial and annual grasses, with 51-52 % increase vs. the control without fertilizers. It was revealed that the long-term use of mineral fertilizers negatively affects the activity of catalase, the redox enzyme. The decrease vs. the control was up to 14 % depending on the culture. The activity of hydrolytic enzymes urease and invertase remained not significantly affected. Observations of the meadow-chernozem soil nitrate regime showed that mineral fertilizers used at a dosage of N60P60 in sorghum-Sudangrass hybrid and grass mixture crops increased the soil nitrate nitrogen content during the growing season by two times or more compared to variants without fertilizers. In our research, the yield of perennial grasses over the years was 3.84-4.57 t/ha DM in the control and 4.82-4.89 t/ha DM upon fertilization. The studied technology of mineral fertilizer application significantly increases the yield of sorghum-Sudangrass (by 1.65 t/ha DM, or by 39 % vs. control. Crop yields had the strongest direct correlation with the microbiota of the nitrogen cycle, the amylolytic and proteolytic microorganisms ( r = 0.98 and r = 0.85, respectively, p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }