A field experiment was conducted with the energy crop Miscanthus giganteus to investigate
the effects of N, K and S fertilisers. Planted in 2003 on a sandy loam soil, treatments
were applied and yield and quality measured during 2005e2007.
Soil Mineral N (SMN) in spring was between 30 and 40 kg ha1 N. The optimum N
application for yield was 100 kg ha1 N, which increased mean gross margin by £132 ha1
and yield by 3.9 t ha1 DM to 13.5 (þ/ 0.46) t ha1 DM compared to zero applied N.
Increasing the rate of application of N increased the concentration of N, K and Cl in the
harvested crop. The background K and S supply was adequate for maximum crop yield.
Adding 50 kg ha1 K as KCl was shown to be the most appropriate way to apply maintenance
dressings with minimal effect on harvested crop K and Cl concentrations. In 2008
e09 a uniform application of 100 kg ha1 N was made over the whole site; there were no
yield effects due to the previous differential applications (mean ¼ 12.85 t ha1 DM).
The work demonstrates the need to take into account all sources of N when considering
N applications to miscanthus. On this relatively poor nutrient retention soil the use of N
fertiliser is clearly justified in financial terms. The use of N and K fertilisers for maximum
yield needs to be balanced against crop quality affects.