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Biochar Improves the Water Retention of Soils
Biochar improves the water retention of soils. A number of studies have investigated the relationship between biochar
and water retention in soils. The results are soil and crop dependent, but studies indicate increased water retention as a
function of biochar addition to soils. For example, Glaser et al. (2002) reported that anthrosols rich in biochar with sur-
face areas three times higher than those of surrounding soils had an increased field capacity of 18%. Novak et al. (2009)
found that increases from 6.7% to 15.9% in soil moisture retention occurred relative to controls in a southeastern coastal
soil. Brockhoff et al. (2010) examined biochar (10% v/v) as a replacement for peat in sand-based turfgrass ecosystems
and found that biochar improved water storage (170% compared to sand), reduced overall water use, and decreased N
fertilizer applications.
Additionally, water retention studies have been conducted with biochar on soils negatively affected by human activities.
On mine impacted soils in Colorado, Peltz et al. (2011) concluded the following:
1. The addition of a 30% by volume amount of biochar increases soil water holding capacity in field settings by >100%
relative to no biochar.
2. Biochar treatments increased water holding capacity in all soils by 90% - 180%.
3. The soil moisture content measurements strongly suggest that biochar improves the water holding capacity of
degraded mine soils.
4. In container trials, biochar additions to soil increased both the soil moisture content and above ground biomass by
>100% and >66%, respectively.
Water retention is improved directly and indirectly when biochar is added to the soil. The direct effect of biochar appli-
cations is related to the large inner surface area of biochar which ranges from 200 to 400 m2/g (Kishimoto and Sugiura
1985). The addition of the highly porous material holds more water than the soils to which it was added.
The indirect effects of biochar application on water retention relate to improved soil structure (see below). Water retention
of soil is determined by the distribution and connectivity of pores in the soil matrix, which is largely affected by soil tex-
ture, aggregation, and soil organic matter content (Brady and Weil, 2004). Biochar has a higher surface area and greater
porosity relative to other types of soil organic matter, and can therefore improve soil texture and aggregation, which
improves water retention in soil.
Factors such as soil temperature, soil cover, evaporation, and evapotranspiration affect soil water availability as well as
the addition of biochar (Sohi et al 2010). The agronomic water-storage benefit of biochar application is dependent on the
relative modification of the proportion of soil pore size in the plant root zone (that is, the relative distribution of micro,
meso and macro pores in the root zone). In sandy soils, the additional volume of water and soluble nutrients stored in
the biochar micropores may become available even as the soil dries. This may lead to increased plant water availability
during dry periods (Verheinjin et al 2009).
Biochar Improves Soil Quality
Soil quality directly affects water retention in soils. Therefore any improvement in soil quality results in better water
retention by the soil and improved availability of water and soluble nutrients by plants. Biochar improves soil quality and
Products Information
Bison Soil Organic Biochar
and Soil Water Retention