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Miscanthus Production
variability independent of typical climatic rainfall and temperature differences and geographic factors such as latitude and altitude.
Lee et al. (2018) observed quite variable responses across sites and years in
the US. Added N at 60 or 120 kg ha −1 was rarely detrimental, and sometimes
beneficial. The work of Lee et al. (2017) in Illinois (~40 N latitude) showed
that very high yields of biomass were obtained with added N, at rates of
60 and 120 kg ha −1 year −1 , but the higher rate gave no improvement over the
60 kg ha −1 rate. Yields were reasonable in the 0 N control plots, but averaged
half the yield of the N-fertilized plots over years 2011–2014, where drought
may have affected yields (see discussion above under water). In other studies,
mass balance calculations suggest that the crop may fix atmospheric N by a
symbiotic association (Davis et al., 2010). Bioavailability of adequate P may be
decreased at high pH in soils with abundant calcium. This combination produces calcium hydroxyapatite, which is quite insoluble at pH 8. Miscanthus
extracts K efficiently from soil, but it seems to be a common practice to add
a small supplement proportional to amounts removed with the crop, especially after several years of harvest.
A significant concern may be overfertilization of Miscanthus, if it is
intended for combustion. This is because high K and high Cl lead to corrosion and slag formation in the combustion chamber. It has been reported that
use of large amounts of biosolids can result in plants taking up excess levels
of these elements, far above disagree strongly what is essential for growth,
lowering the end use value of the biomass (Kołodziej et al., 2016). Those
authors applied “sewage sludge” one time in amounts up to 60 dry matter t
ha −1 and observed that peak productivity was reached at about 10–20 t ha −1
in later harvests, but all levels appeared inhibitory in the first year. Nitrogen
(total) levels in the biosolids were 7.45% with relatively high ammonium N
of 2.35% at the time of application and tilling into 40 cm depth during the
autumn prior to planting Miscanthus. The ammonium presumably volatilized or nitrified over winter. If not, it might be toxic at up to 250 mg kg −1 of the
top 40 cm soil. The cause of first-year inhibition by sewage sludge is unclear,
because there were not high concentrations of toxic trace elements or sodium
according to data presented by the authors. The Zn level in the sludge was
1000 mg kg −1 , which when applied at 60 Mg ha −1 would increase the Zn level
of soil by only 15 mg kg −1 for the top ~40 cm.
A rather different approach was taken by Dubis et al. (2020) who grew
Miscanthus in Poland for 5 years with high applications of mineral fertilizer (90 kg ha −1 of N, 80 kg ha −1 of P 2 O 5 , 120 kg ha −1 of K 2 O), and only then,
after-stable yields were obtained, compared doses of 100 or 160 kg ha −1 of
N applied as sewage sludge (~13 and 20 Mg ha −1 , varying by year) versus
mineral N at comparable rates and 50 kg ha −1 of P 2 O 5 and 100 kg ha −1 of K 2 O
applied to the mineral fertilizer treatments. Overall, yields varied only ~20%
over 6 years, between 17 and 22.5 t ha −1 , presumably as a function of weather,
with control plots consistently ~20% lower than three treatments which did
not differ from one another, and about 10%–15% lower than the lower level of