The current state of the humus content of arable chernozems of the true steppes (the example of the Rostov region, Russia)

Aim. To estimate the humus content and stocks of arable chernozems of two soil-ecological zones (Predcaucasia and Yuzhno-Russkaya) within the Rostov region, as well as the possibility of the optimization of the state of their humus under current conditions.
Material and Methods. The following data sources were used: soil and general geographic information accumulated in the Soil-geographic Database of the Russian Federation information system, the Red Book of the Rostov Region Soils database, digitised archived soil survey data of 1977-1995 and agrochemical monitoring data of 2012-2017.
Results. The stabilisation of the humus content of the arable chernozems of the Predcaucasian zone in recent decades has been demonstrated and can be explained by a decrease in the dehumification rate under minimal tillage. The average humus content in the soils of the Yuzhno-Russkaya zone decreased by approximately 0.5% during the same period, which may be caused by the high proportion of row-crops cultivated in an erosion-prone area. The current average humus content in arable chernozems is very low, it is close to the critical level, below which crop yield is decreased despite of sufficient mineral fertilizers using.
Conclusion. The main causes of soil dehumification in the region are agrogenic humus mineralization due to a constant deficit of compensating amounts of fresh organic matter, deflation of fine soil material from ploughed surfaces and water erosion. The optimisation of land use structure and crop structure, which takes into account the characteristics of these territories, is required to reduce the intensity of these processes under current conditions.

1. Vitousek P.M., Mooney H.A., Lubchenco J., Melillo J.M. Human domination of Earth's ecosystems. Science, 1997, vol. 277, iss. 5325, pp. 494-99. DOI: 10.1126/science.277.5325.494

2. Lal R. Soil carbon sequestration to mitigate climate change. Geoderma, 2004, vol. 123, iss. 1-2, pp. 1-22. DOI: 10.1016/j.geoderma.2004.01.032

3. Sanderman J., Hengl T., Fiske G.J. Soil carbon debt of 12,000 years of human land use. Proceedings of the National Academy of Sciences of the United States of America, 2017, vol. 114, iss. 36, pp. 9575-9580. DOI: 10.1073/pnas.1706103114

4. Smith P. Soil Organic Carbon Dynamics and Land-Use Change. In: Land Use and Soil Resources. Braimoh A.K., Vlek P.L.G. (eds). Dordrecht, Springer, 2008, pp. 9-22. DOI: 10.1007/978-1-4020-6778-5_2

5. Shangguan W., Gong P., Liang L., Dai Y.J., Zhang K. Soil Diversity as Affected by Land Use in China: Consequences for Soil Protection. The Scientific World Journal, 2014, vol. 2014, article ID 913852. Available at: https://doi.org/10.1155/2014/913852 (accessed 23.05.2020)

6. Romanenko G.A., Komov N.V., Tyutyunnikov A.I. Zemel'nye resursy Rossii, effektivnost' ikh ispol'zovaniya [Land resources of Russia, efficiency of their use] Moscow, Russian Agricultural Academy Publ., 1996, 306 p. (In Russian)

7. Shishkina D.Yu. Environmental assessment of the dynamics of agricultural land of the Rostov region. Izvestiya vuzov. Severo-Kavkazskii region. Natural science, 2017, no. 3-1, pp. 122-128. (In Russian) DOI: 10.23683/0321-30052017-3-1-122-128

8. Informatsionnaya sistema «Pochvenno-geograficheskaya baza dannykh Rossii» [Information System «Soil-Geographical Database of Russia»]. Available at: https://soil-db.ru/ (accessed 20.10.2020)

9. Shoba S.A., Aljabina I.O., Golozubov O.M., Ivanov A.V., Ivanov A.L., Kolesnikova V.M., Kryshhenko V.S., Molchanov Je.N., Rozhkov V.A., Sheremet B.V. Informatsionnaya sistema na osnove Pochvenno-geograficheskoi bazy dannykh Rossii (IS PGBD RF) [Information system based on the Soil Geographical Database of Russia (IS SGDB RF)]. Svidetel'stvo o registratsii elektronnogo resursa, no. 19661, 06.11.2013

10. Golozubov O.M., Rozhkov V.A., Alyabina I.O., Ivanov A.V., Kolesnikova V.M., Shoba S.A. Technologies and Standards in the Information Systems of the Soil‐Geographic Database of Russia. Eurasian Soil Science, 2015, vol. 48, no. 1, pp. 1‐10. DOI: 10.1134/S1064229315010068

11. Hoffmann C., Golozubov O., Alyabina I., Heinrich U. Chapter I/12: Standards for the Collection, Management and Provison of Soil Research Data: Two National Case Studies. Novel Methods and Results of Landscape Research in Europe, Central Asia and Siberia (in five volumes). vol. 1. Landscapes in the 21th Century: Status Analyses, Basic Processes and Research Concepts. Мoscow, Publishing House FSBSI «Pryanishnikov Institute of Agrochemistry», 2018, pp. 85‐89. DOI 10.25680/6422.2018.85.59.012

12. Lyuri D.I., Goryachkin S.V., Karavaeva N.A., Denisenko E.A., Nefedova T.G. Dinamika sel'skokhozyaistvennykh zemel' Rossii v XX veke i postagrogennoe vosstanovlenie rastitel'nosti i pochv [Dynamics of agricultural land in Russia and postagrogenic restoration of plants and soils]. Moscow, GEOS Publ., 2010, 416 p. (In Russian)

13. Urusevskaya I.S., Alyabina I.O., Vinyukova V.P., Vostokova L.B., Dorofeeva E.I., Shoba S.A., Shchipikhina L.S. Karta pochvenno‐ekologicheskogo raionirovaniya Rossiiskoi Federatsii Masshtab 1:2500000 [The map of soilecological zoning of the Russian Federation. Scale: 1:2,5 mln]. 2013. (In Russian)

14. Spiridonov A.I., ed. Karta geomorfologicheskogo raionirovaniya SSSR. Masshtab 1:8 000 000 [Map of geomorphological zoning of the USSR. Scale: 1:8 mln]. Moscow, GUGK Publ., 1983. (In Russian)

15. Voskresenskii S.S., Leont'ev O.K., Spiridonov A.I., Luk'yanova S.A., Ul'yanova N.S., Anan'ev G.S., Andreeva T.S., Varushchenko S.I., Spasskaya I.I. Geomorfologicheskoe raionirovanie SSSR i prilegayushchikh morei [Geomorphological zoning of the USSR and adjacent seas]. Moscow, Vysshaya shkola Publ., 1980, 344 p. (In Russian)

16. Bezuglova O.S., Nazarenko O.G., Ilyinskaya I.N. Dynamics of Land Degradation in the Rostov Region. Arid ecosystems, 2020, vol. 26, no. 2(83), pp. 10‐15. DOI: 10.24411/1993‐3916‐2020‐10090

17. Ekologicheskii vestnik Dona. O sostoyanii okruzhayushchei sredy i prirodnykh resursov Rostovskoi oblasti v 2019 godu [Don's ecological bulletin. The state of the environment and natural resources of the Rostov region in 2019]. Ministry of Natural Resources and Ecology of the Rostov Region. Rostov‐on‐Don, 2020, 372 p. (In Russian) Available at: https://xn--d1ahaoghbejbc5k.xn--p1ai/projects/19/ (accessed 20.05.2020)

18. Klassifikatsiya i diagnostika pochv SSSR [Classification and diagnostics of soils in the USSR]. Moscow, Kolos Publ., 1977, 224 p. (In Russian)

19. Sharkov I.N. The concept of humus reproduction in soils. Agrokhimiya [Agrochemistry]. 2011, no. 12, pp. 21-27. (In Russian)

20. Loveland P., Webb J. Is there a critical level of organic matter in the agricultural soils of temperate regions: a review. Soil and Tillage Research, 2003, vol. 70, no. 1, pp. 1-18. Available at: https://www.sciencedirect.com/journal/soil-and-tillage-research/vol/70/issue/1 (accessed 20.05.2020)

21. Janzen H.H., Olson B.M., Zvomuya F., Larney F.J., Ellert B.H. Long-term field bioassay of soil quality. Prairie Soils and Crops Journal, 2012, vol. 5, pp. 165-168. Available at: https://prairiesoilsandcrops.ca/articles/volume-5-17-screen.pdf (accessed: 20.05.2020)

22. Kogut B. M. Assessment of the humus content in arable soils of Russia. Eurasian Soil Science, 2012, vol. 45, no. 9, pp. 843-851. DOI: 10.1134/S1064229312090062

23. Prasolov L.I. About the chernozem of the Azov steppes. Pochvovedenie [Soil science]. 1916, no. 1, pp. 23-46. (In Russian)

24. Chernova O.V., Bezuglova O.S. Principles and Features of the Compilation of the Red Data Book of Soils of the Steppe Regions (on Example of the Rostov Oblast). Arid Ecosystems, 2018, vol. 8, no. 1, pp. 28-37. DOI: 10.1134/S207909611801002X

25. Semenov V.M., Kogut B.M. Pochvennoe organicheskoe veshchestvo [Soil Organic Matter]. Moscow, GEOS Publ., 2015, 233 p. (In Russian)

26. Orlov D.S., Biryukova O.N., Rozanova M.S. Real and apparent losses of organic matter by the soils of the Russian Federation. Eurasian Soil Science, 1996, vol. 29, no. 2, pp. 174-183.

27. Smagin A.V. Dynamics of chernozems: reconstruction and prediction of agrodegradation. Problemy agrokhimii i ekologii [Problemy Agrohimii i Ekologii]. 2012, no 3, pp. 3138. (In Russian)

28. Shoba S.A., ed. Natsional'nyi atlas pochv Rossiiskoi Federatsii [National atlas of soils of the Russian Federation]. Moscow, Astrel', AST Publ., 2011, 632 p. (In Russian)

29. Orlova I.V. Dinamika i sbalansirovannost' struktury zemlepol'zovaniya prigranichnykh stepnykh raionov Zapadnoi Sibiri [Dynamics and balance of the structure of land use in the border steppe regions of Western Siberia]. Steppe bulletin, 2006, no. 21-22. Available at: http://savesteppe.org/ru/archives/2498 (accessed 23.05.2020) (In Russian)

30. Kuznetsov V.V., Gar'kavyi V.V., Lysenko E.G., Tarasov A.N. Ekologiya i proizvodstvo v agrarnom sektore ekonomiki [Ecology and production in the agricultural sector of the economy]. Rostov-on-Don, 1997, 228 p. (In Russian)