The effect of harvest time and pre harvest treatment on the moisture content of Miscanthus × giganteus

• Direct cut and collect yields lower moisture biomass earlier in the harvest window.
• Wilting biomass before collection lowers moisture later in harvest window.
• Wilting biomass in February yields lower moisture relative to the standing crop.

This study aims to determine the most appropriate time to harvest Miscanthus × giganteus between January and April, over three possible harvest windows (Jan, Feb and Mar), relative to the harvest method being employed to cut the crop. The moisture content (MC) of biomass cut in January increased compared to the standing crop (control). From an initial MC of 53% in 2009 and 63% in 2010, the control was 12% and 13% lower than Cut Jan after 4 weeks of the treatment in respective years. The MC of Cut Feb was 19% lower than the control after 4 weeks in 2009. Despite Cut Feb being 4% higher than the control after one week in 2010, both treatments reached 34% MC after 3 weeks. A difference of 16% occurred between the Cut Mar and the control after one week in 2009 while in 2010 Cut Mar was 5% higher than the control after one week. Examining the relationship between stem MC, meteorological parameters and evapotranspiration showed that a combination of relative humidity and evaporation rate (Penman equation.) demonstrated the strongest relationship with crop MC. If harvesting early, lower MC can be achieved by cutting and collecting the crop immediately. An increase in the rate of moisture loss can be achieved later in spring by cutting the material and allowing it to dry for a period of time prior to collection if suitable drying conditions occur. An analysis across several sites showed that such conditions are most likely to occur in February.