Available research to date has shown that biochar al­ters various soil properties in a number of ways. (See Table 26.5.) In the context of the siliceous sandy soils of the West Midlands, the most sought effects are improved microbial habitats and improved nutrient supplies from relatively low (~1 t/ha) rates of biochar use. (See Table 26.6 for crop and pasture research responses in the West Midlands.) It is clear that more research is needed on how various biochars influence the flows of nutrients through the soil profile (Lehmann
et al., 2006; Laird et al., 2008), particularly under Austra­lian conditions (McHenry, 2011). To date, the major claims have been related to biological immobilization of inorganic N, adsorption of dissolved ammonium, ni­trates, P, and hydrophobic organic pollutants (Beaton et al., 1960; Gustafsson et al., 1997; Accardi-Dey and Gschwend, 2002; Lehmann et al., 2003; Bridle, 2004; Mizuta et al., 2004). However, the available research scope does not include an assessment of whether this adsorption could reduce some transport of agricultural fertilizers or other pollutants into ground and surface waters in agricultural catchments (Lehmann et al., 2006; Lehmann, 2007). Early work by Bridle (2004) sug­gested that biochar applications reduce nitrate leaching, as his research found levels of nitrate and ammonium did not change in soils for 56 days after application. The soil incubation study further revealed that in contrast, soil bicarbonate availability and plant available P levels would increase slowly (Bridle, 2004). The labo­ratory results suggested that biochar would provide a source of P for plant growth and could have applications on soils as a slow release form of P, yet some research suggest a reduced uptake of N. This may be more useful in deep sandy soils where P leaches from the surface into groundwater. Biochars are also hypothesized to slow the N cycle by increasing the carbon to N soil ratio, possibly due to increased soil aeration reducing anaerobic conditions (Lehmann et al., 2006). Rondon et al. (2005) found a significant reduction of nitrous oxide emissions, and a near-complete suppression of methane emissions in glasshouse environments at biochar additions of 30 g/kg of soil for some crops (Rondon et al., 2005; Lehmann et al., 2006). However, in some circumstances a high carbon to N ratio and abiotic buffering of mineral N may lead to low N availability (Lehmann and Rondon, 2006). Therefore, medium-scale crop biochar trials are required with regionally common soil biota and mineralogy, and also crop, pasture, and animals for greater understanding of commercial agricultural applicability in a particular region.

ECONOMIC ANALYSIS

A recent analysis by Blackwell et al. (2010) on biochar effects on profitability of dryland wheat production in WA provided a perspective of the breakeven investment costs per hectare of different responses over the medium term. Table 26.7 shows that for the West Midlands area (high rainfall north) a 10% yield increase from 1 t/ha application of banded biochar with a declining response over 12 years would break even at $130/ha, based on the previous 12-year data. This breakeven cost included estimated biochar application costs of between $20 and
$50/ha; thus a production/purchase and transport cost would need to be no higher than about $50—$100/t to enable some income from the biochar use, which encourages further work toward low-cost biochar pro­duction technology development (Blackwell et al., 2010).