BIOCHAR - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 111

(pH KCl 3.9) had no effect on first season maize growth, a significant grain yield increase
during the subsequent three seasons was attributed to greater plant available Ca and Mg in the
biochar treated soil as compared to the control (Major et al., 2010). However, a nil effect of
dairy manure biochar application (22.4 Mg ha -1 ) to a Xeric Haplocalcids soil (pH 7.6) on
silage corn yield in the first season followed by a significant yield reduction in the following
season was attributed to development of N deficiency (Lentz & Ippolito, 2012).
In addition to acidity, nutrient deficiency is another limiting factor for plant growth in
acid soils, caused by the weathering processes during the pedogenic development of acid
soils. Van Zwieten et al. (2010) showed that only upon addition of fertilizer concurrently with
biochar derived from the slow pyrolysis of paper mill did significant increase in wheat yield
occurred in an acid soil (2.5-fold). Similarly, Hossain et al. (2010) found limited
improvement in cherry tomato ( Lycopersicon esculentum ) yield grown in an acid soil (pH
4.6) amended with biochar from wastewater biosolids, which was lower than that achieved by
fertilizers alone. Plant productivity nearly doubled upon using biochar in combination with
fertilizer (Hossain et al., 2010). The marked response in plant growth to fertilizer application
in biochar-amended soils suggests that inasmuch as biochar likely ameliorated soil acidity,
nutrient availability limits plant growth.
A combined effect of increasing soil pH and supplementing crop nutrient requirement is
likely to be achieved by using biochar from animal waste feedstock such as chicken and dairy
manure. A marked positive effect of chicken manure biochar on crop productivity was found
(Jeffery et al., 2011), likely due to the high nutrient load in the chicken manure biochar. As
shown by Hass et al. (2012), adequate nutrient levels and excess available P can be expected
in chicken manure biochar amended soil. Applying cow manure biochar to a sandy soil (pH
6.4) at rate of up to 20 Mg ha -1 resulted in increase in maize grain yield, dry matter, water use
efficiency, and grain nutrient content at biochar application rates of 15 and 20 Mg ha -1 , but
not at 10 Mg ha -1 (Uzoman et al., 2011b). Applied to an acidic ferralsol (pH 4.7), Slavich et
al. (2013) showed contrasting effects of feedlot manure and green waste biochars on
productivity of annual ryegrass ( Lolium multiflorum ) and peanut. While the manure biochar
increased both productivity and N use efficiency of annual ryegrass and dry matter yield of
peanut, no improvement was noticed by green waste biochar. The authors attributed the
differences to higher total (6900 and 190 mg kg -1 ) and available P (73 and 6 mg kg -1 ,
respectively) in the manure biochar compared to the green waste biochar, which were still
maintained at higher levels in the soil three years after application (Slavich et al., 2013). In a
similar soil type, Van Zwieten et al. (2013) showed increase in fresh corn cob yield in a field
treated with poultry manure biochar applied at the same N-level as urea treated corn. While
resulting in similar yield and corn N content as in raw poultry manure treatment, biochar
treatment resulted in lower levels of N 2 O emission and carbon mineralization rate (Van
Zwieten et al., 2013).
Crop productivity response to biochar application was found to also be plant-type
dependent, where annuals did better than perennials and legumes better than some grasses
(Jeffry et al., 2011; Biederman & Harpole, 2012). As the spread between the native soil pH
and the pH at which optimal growth condition of a given plant increases, a reduction in
performances is expected; and narrowing the pH gap will improve plant performances. Nil to
adverse effect of biochar on ryegrass productivity in acid soils (Jeffery et al., 2011) is likely
to the fact that ryegrass is an acid tolerant plant and hence may not benefit much from an
increase in soil pH, which may not have been the limiting factor for ryegrass yield, and in fact