Soil organic carbon in long–term experiments: comparative analysis in Slovakia and Serbia

M. Macák¹, I Đalović²*, J. Turan², S. Šeremešić³, S. Tyr¹, D. Milošev³ and M. Kulina⁴

¹Slovak Agricultural University in Nitra, Faculty of Agrobiology and Food Resources, Tr. A. Hlinku 2, SK949 76 Nitra, Slovak Republic
²Institute of Field and Vegetable Crops Novi Sad, Department for Maize, RS21000 Novi Sad, Maxim Gorki 30, Serbia
³University of Novi Sad, Faculty of Agriculture, Department of Field and Vegetable Crops, Sq. Dositeja Obradovica 8, RS21000 Novi Sad, Serbia
⁴University of East Sarajevo, Faculty of Agriculture, Vuka Karadzića 30, Istočno Novo Sarajevo, Republic of Srpska, Bosnia and Herzegovina
*Correspondence: maizescience@yahoo.com; ivica.djalovic@ifvcns.ns.ac.rs

Abstract:

Soil organic carbon plays an important role in a long-term agroecosystem productivity, in the global C cycle, maintaining a soil nutrient pool and improving its availability. The objective of this study is the assess the impacts of long–term cropping practices on SOC dynamics in Slovakia and Serbia. Soil C sequestration is a complex process that is influenced by many factors, such as agricultural practice, climatic and soil conditions. For the both location the initial SOC decline was followed with the C stabilization and possible increase where proper practices were used. More intensive crop management systems that maintained residue cover provided the greatest benefit towards increasing the quantity of mineralizable nutrients within the active fraction of soil organic carbon (SOC), as well as increasing C sequestration as SOC. Long–term field experiments have contributed significantly to our current knowledge of soil quality and have been used to study the influence of crop management, fertilizer application and tillage practices on SOC content.

Key words:

Standard and modified methods for soil organic carbon determination in agricultural soils

A. Slepetiene¹, J. Slepetys¹ and I. Liaudanskiene¹

¹Lithuanian Institute of Agriculture, Instituto al.1, LT 58344, Dotnuva, Akademija, KedainiaiDistrict, Lithuania; e-mail: alvyra@lzi.lt
¹Lithuanian Institute of Agriculture, Instituto al.1, LT 58344, Dotnuva, Akademija, KedainiaiDistrict, Lithuania; e-mail: jonas.slepetys@lzi.lt
¹Lithuanian Institute of Agriculture, Instituto al.1, LT 58344, Dotnuva, Akademija, KedainiaiDistrict, Lithuania; e-mail: inga@lzi.lt

Abstract:

The presented study demonstrates the benefits of using modified vertical photometry methods for rapid, reliable and accurate soil organic carbon determination in agricultural soils. For tests we selected and analysed 25 arable (Ap horizon) topsoil (Cambisol) samples, so that the determined values cover as wide a range as possible. In the proposed method soil organic carbon is determined using 0.2 M potassium dichromate solution in diluted (1:1) sulphuric acid. The data obtained using the proposed method correlated strongly with the data obtained by Vario EL and titration methods. The new modification safeguards the objectivity of results, since it gives strong correlation coefficients (r = 0.989–0.990, P < 0.001, n = 25) with the dry combustion method data. The findings suggest that different photometers did not significantly affect results. However, comparison of conventional photometry and photometric determination using Multiskan MS equipped with the Genesis Lite microplate software revealed the following advantages of the latter technique: higher measurement accuracy, the facility to edit and save calibration graphs, the possibility of optimized and multiple replications, higher labour efficiency; improved safety for research personnel and lower reagent consumption. Strong and highly significant (P < 0.001) correlations were determined between the data obtained using different methods, and respective linear regression equations for the re-calculation of SOC values were developed.

Key words:

agricultural soils, determination methods, soil organic carbon