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The objectives of the research were to: (1) assess the strength of relationships between the soil thermal and hydrophysical properties, (2) evaluate the strength of association of evapotranspiration of spring wheat crop with soil thermal and hydrophysical properties, and (3) estimate the ranges of the thermal and hydrophysical properties of the sandy Haplic Podzol during the growing period of spring wheat in 2022. The study included instrumental simultaneous measurements of meteorological data, soil water retention curve, soil moisture content (SMC) and thermal properties. Actual evapotranspiration was calculated according to the Allen equation. Spearman’s rank correlation coefficients showed that the increase in SMC from 0.10 cm3 cm−3 to 0.26 cm3 cm−3 resulted in a significant increase in thermal conductivity (r = 0.81, p < 0.001), volumetric heat capacity (r = 0.93, p < 0.001) and thermal diffusivity (r = 0.94, p < 0.001). Actual evapotranspiration also rose with the increasing SMC (r = 0.91, p < 0.001) and matric water potentials (r = 0.61, p < 0.05). As a consequence of the changes in SMC, the Spearman’s rank correlation coefficients supported the strong positive relationships of actual evapotranspiration with volumetric heat capacity (r = 0.97, p < 0.001), thermal conductivity (r = 0.96, p < 0.001) and thermal diffusivity (r = 0.96, p < 0.001). Pearson correlation coefficients also supported the strong input of thermal inertia to the actual evapotranspiration (r = 0.88, p < 0.01). During the whole period of observations, actual evapotranspiration varied from 0.05 to 0.59 mm hr−1, soil thermal conductivity – from 0.225 to −1.056 W m−1 K−1, volumetric heat capacity – from 1.057 to 1.889 MJ m–3 K−1, heat diffusivity from 0.189 to 0.559 mm2 s−1, and thermal inertia – from 516 to 1412 J m−2 K−1 s−0.5.

It was shown that the use of biochar provides many benefits to agriculture by improving the whole complex of soil properties, including soil structure. However, the diverse range of biochar effects depends on its physicochemical properties, its application rates, soil initial properties etc. The impacts of biochar, mainly its reapplication to soils and its interaction with nitrogen in relation to water-stable aggregates (WSA) did not receive much attention to date. The aims of the study were: (1) to evaluate the effect of initial application (in spring 2014) and reapplication (in spring 2018) of different biochar rates (B0, B10 and B20 t ha−1) as well as application of biochar with N-fertilizer (40 to 240 kg N ha−1 depending on the requirement of the cultivated crop) on the content of WSA as one of the most important indicators of soil structure quality, (2) to assess the interrelationships between the contents of soil organic matter (SOM) and WSA. The study was conducted in 2017–2019 as part of the field experiment with biochar on Haplic Luvisol at the experimental station of SUA in Nitra, Slovakia. Results showed that initial application as well as reapplication of biochar improved soil structure. The most favorable changes in soil structure were found in N0B20B treatment (with biochar reapplication) at which a significantly higher content of water-stable macro-aggregates (WSAma) (+15%) as well as content of WSAma size fractions of > 5 mm, 5–3 mm, 3–2 mm and 2–1 mm (+72%, +65%, +57% and +64%, respectively) was observed compared to the control. An increase in SOM content, due to both, initial biochar application and its reapplication, significantly supported the stability of soil aggregates, while organic matter including humic substances composition did not.

Soils are one of the main sources of nitrous oxide (N2O) in agriculture. Soil management practices can significantly affect N2O emissions through changing soil physical, chemical and biochemical properties. Application of biochar to arable soils can be an option for N2O emission mitigation, but the effect of biochar can be different for soils with different fertility levels. The objective of this study was to evaluate the effect of biochar application on N2O emission, soil properties and barley yield from loamy sand Stagnic Luvisol with high and medium levels of fertility caused by high rates of farmyard manure and fertilizer application for 10 years. A small-scale field experiment was conducted during the growing season of 2012 in North-Western Russia. Four treatments were used in the experiment: 1) control (no biochar, no N-fertilizer), 2) biochar (12 t ha-1), 3) N-fertilizer (90 kg ha-1 N) and 4) biochar (12 t ha-1) + N-fertilizer (90 kg ha-1 N), in five replicates. Significant changes in water-holding capacity and the amount of available nitrogen (N) occurred in the soil with high fertility, and thus it emitted significantly more N2O for the growing season than the soil with medium fertility. Biochar application effect on N2O emissions depended on the soil management history and was reducing the emission from the soil with high fertility rich in mineral N and C but not from the soil with medium fertility if no nitrogen fertilizer was applied to the latter soil. The yield-scaled N2O emission was the highest from the control treatments for the soil with both fertility levels, and the soil with high fertility was always characterized by higher yield-scaled N2O emissions than the soil with medium fertility. Application of biochar reduced yield-scaled N2O emission from the soil with medium and high fertility levels showing that biochar application to the soil can improve N use by the plants. [ABSTRACT FROM AUTHOR]

The benefits of biochar application are well described in tropical soils, however there is a dearth of information on its effects in agricultural temperate soils. An interesting and little explored interaction may occur in an intensive agriculture setting; biochar addition may modify the effect of commonplace N-fertilization. We conducted a field experiment to study the effects of biochar application at the rate of 0, 10 and 20 t ha-1 (B0, B10 and B20) in combination with 0, 40 and 80 kg N ha-1 of N-fertilizer (N0, N40, N80). We followed nitrous oxide (N2O) emissions, analysed a series of soil physicochemical properties and measured barley yield in a Haplic Luvisol in Central Europe. Seasonal cumulative N2O emissions from B10N0 and B20N0 treatments decreased by 27 and 25% respectively, when compared to B0N0. Cumulative N2O emissions from N40 and N80 combined with B10 and B20 were also lower by 21, 19 and 25, 32%, respectively compared to controls B0N40 and B0N80. Average pH was significantly increased by biochar addition. Increased soil pH and reduces NO-3 content seen in biochar treatments could be the two possible mechanisms responsible for reduced N2O emissions. There was a statistically significant increase of soil water content in B20N0 treatment compared to B0N0 control, possibly as a result of larger surface area and the presence of microspores having altered pore size distribution and water-holding capacity of the soil. Application of biochar at the rate of 10 t ha-1 had a positive effect on spring barley grain yield. [ABSTRACT FROM AUTHOR]