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Phytotechnology with Biomass Production
applied sludge. This experiment indicated that for this soil, adding back N at
the level that it is withdrawn by harvest is beneficial. Harvest was done relatively early in autumn, when only 1/3 of leaves up the stem had dried, for use
in silage for biogas production. Thus, the offtake of N was much greater than
it would be in a late winter harvest. For instance, Kołodziej et al. (2016) saw a
decrease of nearly two-fold in ash content of M. × giganteus when comparing
autumn with spring harvested material. Iqbal et al. (2017) showed that offtake varies with harvest date at multiple locations with multiple CVs, consistent with the estimate that early harvest before nutrient translocation would
remove 100–160 kg year −1 of N, while later winter harvest would decrease
this to 1/2 or 1/3 the amount. For combustion, lowered total mineral content
is very important, whereas for biogas production it is not.
5.5 Role of Soil Amendments
Inorganic commercial fertilizers contain N, P, K, as their main nutrients
in the form of various salts, sometimes with Ca, Mg, Zn, S, B, or trace elements added for specific soil types. These along with different organic fertilizers (compost, ash, manure, activated carbon) have historically been the
primary soil amendments (Antonkiewicz et al., 2019; Boakye-Boaten et al.,
2016; Lehmann et al., 2003). In the last 25 years different wastes like sewage sludge and digestate are becoming popular as soil amendments as well
(Antonkiewicz et al., 2020; Kirchmann et al., 2017; Tabak et al., 2020). In addition, biochar, the solid material obtained from the carbonization of biomass/
waste or through pyrolysis, is currently proposed as both a soil amendment
and carbon sequestration medium (Agegnehu et al., 2016; Faria et al., 2018;
Lehmann et al., 2006). Application of soil amendments boosts the soil fertility balance and improves soil quality, resulting in increased crop yields
(Hu et al., 2018; Humentik et al., 2018). Improvements in soil fertility result
in greater uptake of macronutrients and micronutrients by plants, mainly in
the second cropping season, and higher biomass productivity. Soil benefits
include optimizing soil pH, increasing moisture holding capacity, attracting
more beneficial fungi and microbes, improving cation exchange capacity,
and retaining nutrients. These benefits have been shown to increase yield in
biomass and crops under variable conditions (Chan et al., 2008). One obvious energy cycle is to grow Miscanthus, pyrolyze it to recover energy, and
use the residual biochar as a source of minerals and carbon for Miscanthus
cultivation again.
The impacts of application of different soil amendments to the production of energy crops on regular agricultural soils are well represented in the
literature. However, the improvements of biomass production when these
crops are produced on marginal or contaminated soils are not researched