Organic farming is designed to maintain soil fertility and to assist biodiversity restoration. Developing of methods for assessment of ecological and biological state of soil under organic agriculture is becoming an increasingly urgent task. The purpose of the current work is to evaluate the capabilities of an integrated indicator to identify significant differences in ecological and biological soil states under organic and traditional farming management. The proposed integral indices were calculated on the basis of the number of trophic groups of microorganisms, ecological and trophic indices, and nitrogen and humus soil content.
The studies were performed on gray forest soils of the two farms located in the Mamadyshsky and Vysokogorsky districts of the Republic of Tatarstan. The soils of fields with traditional farming and fields where the organic farming system has been used for 3–5 years were compared. In the samples taken in 2019, the following parameters were determined: the content of humus and total nitrogen, the number of 6 trophic groups of microorganisms, the coefficient of mineralization, and the index of pedotrophy.
The studied parameters were ranked in the following order of informativeness for separating soils of organic and traditional fields: the number of amylolytics and actinomycetes > the number of ammonifiers > the number of cellulose-decomposing microorganisms, pedotrophs, micromycetes > the content of humus, total nitrogen> the index of pedotrophy, the coefficient of mineralization / immobilization. The variability in the number of trophic groups of microorganisms is generally medium and high. The values of the studied parameters, in addition to the number of pedotrophic and cellulose-destroying microorganisms, increased in the following order: soils of traditional fields < soils of organic fields < virgin soils. The number of pedotrophs and cellulose-destroying microorganisms, on the contrary, decreased from traditional fields to virgin areas, therefore, to calculate the integral indicator of the biological state of soils (IPBS), it was decided to use not just the point obtained from the number of these groups of microorganisms, but the inverted value «100 – point».
The calculation of the integral indicator of the biological state of soils was carried out first using all 10 studied parameters, and then 8, 6, and 3 of the most informative ones. The least informative ones were excluded from the calculation. It was shown that the IGBP reflected the level of anthropogenic loads in all cases.
When all 10 parameters were used, the integral indicator changed naturally in the following order: virgin background area – organic fields – traditional fields. The maximum value of the integral indicator of the biological state was observed in the virgin area, which is distinguished by the best biological state of soils, in organic fields the values of the integral indicator are lower, and in traditional fields – the lowest. With a sequential decrease in the number of parameters, this pattern does not change. The highest values of the integral indicator are always observed in the virgin area – 100 %. The lowest are found in the soils of fields with traditional farming. The processing of the results showed that the differences between the soils of organic and traditional fields according to the IPBS were statistically significant in the Mamadyshsky district using 8 parameters, in Vysokogorsky – 3 parameters for calculating the IPBS.
Thus, in order to identify changes in the biological state of soils during the transition from traditional to organic farming after 3–5 years of practice, 3–8 of the most informative microbiological and agrochemical parameters are sufficient. Nevertheless, the search for less labor-consuming and less variable parameters for calculating the IPBS should be continued.
Organic Farming Provides Reliable Environmental Benefits but Increases Variability in Crop Yields: A Global Meta-Analysis
