Effect of biochar application on the physical properties of Haplic Podzol

- Positive effect of biochar application on soil physical properties.
- Reduced soil compaction, improved soil aeration, and increased AWC.
- Short-lasting effect of biochar, limited primarily to the first two years.
- Biochar application to soil - an alternative method of biomass utilization.

The paper presents the results of a study on the effect of biochar application to soil on the basic physical properties of Haplic Podzol. In a six-year (2010-2015) field experiment, the physical properties of biochar-amended Haplic Podzol originating from glaciofluvial fine-grained loamy sand (LS) were studied. The experiment was carried out on three plots with an area of 5.0 m2 each. Biochar produced from wheat straw in the process of pyrolysis at 650 °C was applied to the soil in the following rates: treatment A - 45.0 Mg ha−1, treatment B - 30.0 Mg ha−1 and treatment C - Control (soil without the addition of biochar). Biochar was applied to the soil (April 2011) and mixed with the soil surface layer (0-10 m). Soil samples, their natural structure preserved intact, were collected six times (sampling dates 0-V), once a year, during the vegetation season - after harvest (2nd decade of August). Soil samples were taken from layers: 0-10 cm, 10-20 cm and 20-30 cm, in six replicates, using 100 cm3 metal cylinders. The following physical properties of the soil were determined: particle density (PD), bulk density (BD), total porosity (TP), field air capacity at the potential of −15.5 kPa (content of macropores with Φ > 20 μm - FAC), air permeability at the potential of −15.5 kPa (FAP), water content at sampling (SM), field water capacity (at −15.5 kPa) (FC), available water content (AWC), unavailable water content (UWC), and the ratio FC/TP was calculated. Analysis of the results indicated a positive effect of biochar application on most of the studied physical properties. Compared to soil without biochar addition, soil compaction was lower, there was an improvement in the soil air properties (FAC and FAP) and an increase in water available to plants (AWC). It should be emphasized, however, that the effect of biochar was short-lived, and also limited in depth as it related mainly to the layer of 0-10 cm. The positive effect of biochar on the soil properties was observable mainly at sampling dates I and II. Starting from sampling date III, the differences noted in the values of the soil properties under study gradually diminished, and at sampling date V they virtually disappeared. The statistical evaluation of the results confirmed the observed impact of biochar on the soil, its range and stability. It demonstrated that the effect of biochar on the soil is positive but short-lasting, as starting with the second year after biochar application (sampling date II) its decrease was noted.