The yield and quality response of the energy grass Miscanthus × giganteus to fertiliser applications of nitrogen, potassium and sulphur

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 2005–2007.

Soil Mineral N (SMN) in spring was between 30 and 40 kg ha⁻¹ N. The optimum N application for yield was 100 kg ha⁻¹ N, which increased mean gross margin by £132 ha⁻¹ and yield by 3.9 t ha⁻¹ DM to 13.5 (+/− 0.46) t ha⁻¹ 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 ha⁻¹ 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 2008–09 a uniform application of 100 kg ha⁻¹ N was made over the whole site; there were no yield effects due to the previous differential applications (mean = 12.85 t ha⁻¹ 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.