YIELD INCREASES OF THE BIOMASS CROPS SALIX VIMINALIS AND MISCANTHUS GIGANTEUS: A LOOK TO THE FUTURE - Economics of Sustainable Energy in Agriculture - page 85

approach refers to actual yields, i.e. the yields obtained by farmers. It
estimates the shortfall relative to potential yields, i.e. the yields under
optimal conditions, which can be quantified by physiological crop growth
models.
3. RESULTS
3.1 Analysis of statistical trends in current crops
3.1.1 Winter wheat and other cereals
As a first example for cereals, data on winter wheat are analysed. Figure
7.1 shows the increase in farmer's yield of winter wheat in the Netherlands,
in terms of grain yield and total above-ground yield in the period from
1946 to 1993.
In this period grain yield of winter wheat increased exponentially
with an annual rate of 2.07 %. The increase in grain yield cannot be solely