Differences in soil organic matter and humus of sandy soil after application of biochar substrates and combination of biochar substrates with mineral fertilizers

Abstract

The effort to achieve the sustainable farming system in arable soil led to the intensive search for a new solution but an inspiration can also be found in the application of traditional methods of soil fertility improvement as it is shown in numerous examples in history. Recently many scientific teams have focused their attention on the evaluation of biochar effects on soil properties and crop yields. Since there are a lot of knowledge gaps, especially in explanations how biochar can affect soil organic matter (SOM) and humus substances, we aimed this study at the solution of these questions. Therefore, the objective of the experiment was to evaluate the impact of two biochar substrates (B1 – biochar blended with sheep manure, and B2 – biochar blended with sheep manure and the residue from the biogas station) at two rates (10 and 20 t ha-1) applied alone or in combination with mineral fertilizers (Urea was applied in 2018, at rate 100 kg ha-1, and Urea at rate 100 kg ha-1 + AMOFOS NP 12-52 at 100 kg ha-1 were applied in 2019) on the quantity and quality of SOM and humus of sandy soil (Arenosol, Dolná Streda, Slovakia). The results showed that application of the biochar substrates together with mineral fertilizers (MF) had more pronounced effect on the organic matter mineralization in the sandy soil which resulted in low accumulation of soil organic carbon (Corg) and labile carbon compared to biochar substrates treatments without MF. The share of humic substances in Corg significantly decreased by 16, 50, 16 and 24% in B1 at 10 t ha-1, B1 at 20 t ha-1, B2 at 10 t ha-1 and B2 at 20 t ha-1 treatments, respectively, compared to the control. A similar tendency was observed for biochar substrates treatments + MF, compared to MF control. The carbon content of humic substances (CHS) was equal to 4.40 – 5.80 g kg-1 and the biochar substrates had statistically significant influence on CHS content. On average, there was a smaller decrease of CHS in B1 at rate 10 t ha-1 than at rate 20 t ha-1 and no effect of B2 compared to control. The carbon content of fulvic acid (CFA) was 9% higher in B1 at 10 t ha-1, and 20 t ha-1, 47% higher in B2 at 10 t ha-1 and 17% higher in B2 at 20 t ha-1 compared to control. As a result of biochar substrates + MF application, the reduction in CFA was observed. The results showed a decrease of CHA : CFA ratio with association to biochar substrates alone application compared to control on one hand, and a wider of CHA : CFA ratio in biochar substrates + MF treatments in comparison to MF control on the other hand. Humus stability was increased in biochar substrates alone treatments compared to control, on the other hand, compared to MF control, the application of biochar substrates + MF resulted in a lower humus stability.

Addition of Biochar and Fertiliser Drives Changes in Soil Organic Matter and Humic Substance Content in Haplic Luvisol

“…For this reason, little is known about its effects on the speed of humification and the creation of humic substances or their stabilisation in the soils. Several authors have stated that biochar application holds significant potential for forming and stabilising soil humic substances [27,28,[55][56][57][58][59][60]-a conclusion supported by our research, but only in the case of both biochar doses combined with the second level of nitrogen fertilisation (Table 3). However, if it is applied at a dose of 10 or 20 t ha −1 alone, or in combination with the lower level of N fertilisation, to Haplic Luvisols in a mild climate, it has no significant effect on the humic substances in the soil.…”

Managing soil organic matter through biochar application and varying levels of N fertilisation increases the rate of water-stable aggregates formation

“…As indicated by several recent studies (Bai et al, 2022;Balashov et al, 2021;Głąb et al, 2016;He et al, 2022;Horák et al, 2020;Igaz et al, 2018;Juriga et al, 2021;Saravanan and Kumar, 2022;Šimanský et al, 2018), biochar is considered a promising agronomic tool for modifying soil properties. However, different effects of various biochars on soils were recorded (Bai et al, 2022;El-Naggar et al, 2019;Horák et al, 2020;Hossain et al, 2020;Šimanský et al, 2022;Šrank and Šimanský, 2020). Biochar application to soils can cause both a positive and a negative priming effect, and depending on this effect, an increase or decrease in SOC will be observed.…”

“…Biochar can be an excellent agronomic as well as an environmental tool for increasing SOM content and for mitigating the flux of CO2 from arable land into the atmosphere (Balashov et al, 2021;He et al, 2022;Juriga et al, 2021;Saravanan and Kumar, 2022;Šimanský et al, 2018). Biochar is a significant source of stable organic C (Fisher and Glaser, 2012;Šrank and Šimanský, 2020). After biochar application, as a rule, the entire complex of chemical, physical and biological properties of soils changes (Balashov et al, 2022;Juriga et al, 2021;Šimanský et al, 2022;Zheng et al, 2022), which also can result in higher yields of cultivated crops (Bai et al, 2022).…”

“…Nevertheless, there are several knowledge gaps in this issue. For example, biochar application increases SOM content (Fisher and Glaser, 2012;Šrank and Šimanský, 2020). However, to the best of our knowledge, an explanation of how this increase in SOM content affects the rate of water-stable aggregate formation (particularly as a result of interactions between different N and biochar rates) is not available.…”

Effects of slow and fast pyrolysis biochar on N2O emissions and water availability of two soils with high water-filled pore space

“…Because of high chemical stability, biochar has a great potential to enhance atmospheric carbon sequestration (Laird et al, 2008;Lehmann et al, 2006). Soil amendments such as biochar, composts or their mixtures can decrease soil bulk density (Abd El-Mageed et al, 2021;Hardie et al, 2014), improve soil structure (Ajayi and Horn, 2016;Juriga et al, 2021), increase soil pH (Horák, 2015) cation exchange capacity (Igaz et al, 2018;Jien and Wang, 2013), soil N availability (Haider et al, 2017;Van Zwieten et al, 2010), organic carbon content (Ajayi and Horn, 2016;Šrank and Šimanský, 2020), soil porosity (Blanco-Canqui, 2017;Githinji, 2014), available water content (Głąb et al, 2016;Ibrahim et al, 2013) and saturated hydraulic conductivity (Jien and Wang, 2013;Toková et al, 2020). Syakila and Kroeze (2011) reported that agricultural N2O emission in 2006 reached 23-31% of the global emissions with the main source being nitrogen fertilizer and manure application to soils.…”