Effect of Different Tillage Systems and Soil Biostimulants on Agrochemical Properties and Intensity of Soil CO2 Emission in Wheat Crop

Abstract

In this study, a field experiment was performed at the Experimental Station of Vytautas Magnus University Agriculture Academy in Lithuania from 2018 to 2020. The researched soil comprised carbonate deeper gleyic leachate (IDg4-k) (Calc(ar)i Endohypogleyic Luvisol) (LVg-n-w-cc). A two-factor field experiment was performed on spring and winter wheat. Factor A was soil tillage technology; factor B was the use of biostimulants and their mixtures (Ruinex, Penergetic, Azofix). The experimental fields were arranged randomly in four replicates. The aim of the work was to assess the soil CO2 emissions, soil carbon, soil nitrogen, humus, and humic substances using two different soil tillage management methods (no till—wheat straw left on the soil surface; and reduced till—soil incorporation of the wheat straw) and different biostimulants or nitrogen fertilization. The humus content of the soil remained sufficiently stable or slightly decreased when the straw was retained and the single-component biostimulators Azofix, Ruinex, and Penergetic were used. In contrast, when continuous straw application was combined with two- or three-component mixtures of these biological preparations or with compensatory nitrogen the humus content increased. Compared with the initial state, it increased by 1.4–12.8 % due to the improved complexity of extra conditions for microbiological biodiversity. Meanwhile, after three years of investigation, the soil tillage technology did not significantly impact the humus content, total nitrogen, and CO2 emissions. Tillage technologies had a significant impact on the content of water-soluble soil carbon. Under no-till, the carbon content increased by an average of 9.0%, and under reduced tillage, the carbon content increased by only 2.3%. It is likely that the combination of no-till with catch crops increased the stocks of soluble C in the soil. Compared to the use of compensatory nitrogen, this indicator was increased by all biostimulants, especially when using all three preparations in the mixture (Ruinex, Penergetic, Azofix). The effect of the two-preparation mixtures was also more pronounced than that of the single component. The results over three years show that biostimulants promote the release of mobile humic substances and mobile humic acids better than compensatory nitrogen for straw decomposition. The effect was the same for the organic carbon content.