How to interpret the miscanthus yield maps
The aim of these regional yield maps is to identify potential miscanthus yields within England.
The guidance below must be referred to when using the yield maps for assessing opportunities and optimum sitings of miscanthus. Information about how the maps have been generated is provided below along with the limitations of the model.
IMPORTANT - The information supplied by the miscanthus yield maps is for guidance only and is not intended to fully substitute for professional agricultural advice. Each new planting proposal should be considered on a case by case basis. The user is responsible for any commercial decisions taken based on information presented in the maps.
Background information on how the map was generated
The model estimates total above-ground dry-matter yields at final harvest (tonnes dry matter ha-1 yr-1), and is driven by cumulative temperature and incident radiation. It is not formulated to reflect yield-limiting responses to environmental factors such as pH stress, exposure, wind speeds and nutrient deficiency. For many locations, water availability is a significant environmental factor that may restrict Miscanthus x giganteus from reaching its potential yield therefore the model does endeavour to reflect water limitations on potential crop growth. Temperature is a key driver in the model and so the impact of frost days on the yield is also included.
To translate site-specific results into a national picture of estimated yields, the model is applied over a number of years, using weather data from 5 x 5 km grid squares. Average yield estimates for each grid have been categorised into a suitability index of M. x giganteus in each 5 x 5 km square, assuming an economic harvestable average yield threshold of 12 tonnes dry matter ha-1 yr-1 for an established crop.
Model limitations
These yield estimates are intended for guidance only, at the appropriate regional scale and cannot therefore reflect the details of local climate, aspect, soil types and husbandry and other historical factors. Therefore when interpreting the yield maps it is important to consider the following limits of the model:
- The model estimated yields are for established crops only and the suitability map does not therefore reflect the variation in years to establishment that has been observed at the 7 trial sites.
- Yield estimates are averages determined from running the model with 30 years of statistical weather data for the period 1971-2000. An area, which on average falls in the ‘suitable class’, may still therefore fail to reach the economic threshold in any given year.
- Yields will also vary from the regional estimate due to the variation in local soils, which may result in different estimates of water availability. The average yields in each grid square have been estimated using the dominant soil type. In addition, soil structure, the presence of soil pans, drainage and soil pH are not included in the current model but are likely to impact on yields owing to their influence on crop available water.
- The model assumes that the soil is at field capacity at the beginning of the growing season. It is feasible that in some years a residual soil water deficit may still be evident in the spring, which would impact on yields.
For more detail on the model please refer to Defra project report NF0405: Continued assessment of the agronomy and yield potential of miscanthus for industrial cropping in the UK , or contact John Garstang, ADAS UK Ltd on 01954 268243 or John.Garstang@adas.co.uk
Page last modified: 13 June 2007
Page published: 11 May 2007