92
Phytotechnology with Biomass Production
but the applied N rate is generally used in determining the proper amounts to
apply (USEPA, 1994). In addition, high iron in biosolids will increase trace element sorption capacity of the receiving soil. High organic matter will contribute to both trace elements and organic contaminant retention. Further, high
organic carbon will promote microbial activities, enhancing organic contaminant degradation, and nutrient cycling. Biosolids applications are also limited
by concentrations of specific toxic elements (e.g., As, Pb, Cr, Cd, Zn); however,
regulated biosolids (such as Class A and B biosolids in the USA) contain very
low levels of trace elements. The field experiment at Ft. Riley, KS, had one
treatment of biosolids in its design (Alasmary, 2020).
Other nutrient amendments of soil might include other sources of organic
matter such as composted animal confinement wastes. These are a useful
source of N, P, K but in varying amounts depending on the animal source
and the diet of the animals, which will be very different for ruminants,
nonruminant mammals, and poultry. Waste from nonruminants is often
very high in P, to the extent that struvite mineral (magnesium ammonium
phosphate) can be recovered in large quantities by intentional treatments
(Castro-Diaz S., personal communication). In some settings excess P may be
the limiting factor for biosolids application. Optimum pH for Miscanthus
growth is about 5.5–8. Acidic soils would benefit by application of lime to
raise pH into this range. Both calcium and magnesium are essential for
crop growth. Based on harvested material in winter, Miscanthus biomass
removes relatively little N, P, or K from soil, about 5 kg t −1 of N, 0.5 kg t −1 of
P, and 7 kg t −1 of K (Iqbal et al., 2017). Earlier harvest before leaf fall, nutrient
translocation, and rainfall leaching of biomass will remove more, often a lot
more. As mentioned above, Nagara CV of M. × giganteus was noted to retain
3/4 of the leaf N when injured by fall freezing (Sage et al., 2015). Hence an
early harvest may remove 20 kg t −1 .
Very often it has been observed that added N does not benefit a Miscanthus
crop in the planting year. In some situations, added N is beneficial in later
years. As recognized by Lee et al. (2017), some locations receive higher levels of N deposition from the atmosphere than others do. Places with highdensity animal production may release higher amounts of ammonia to the
atmosphere from hydrolysis of urea. At Konza prairie, a relatively “pristine”
preserve, near Kansas State University, nitrogen deposition in rainfall and
particulates amounted to ~10 kg ha −1 year −1 over the first 18 years of the
21st century, although there appears to be a downward trend to <9 kg ha −1
year −1 in the past decade. Lee et al. (2017) suggested that deposition rates
were significantly higher in Europe. A reported value of 14 kg ha −1 year −1
for Germany may be found at Schaap et al. (2017). For the UK, the historic
trend is downward in this century and reported as about 10 kg ha −1 year −1
in 2010 (Tomlinson et al., 2011). For some regions of the UK deposition rates
were at least two-fold higher in the 1990s when early studies of Miscanthus
were done. The reported deposition rates could support a yield of several
Mg ha −1 without depleting soil N at all. This is an example of large geographic