Total income is greater than r (<1) times the current income even if the area allocation is changed. However, it was not possible to attain an ideal outcome in which all the self-sufficiency rates are equal to or exceed 100 per cent (r = 1) at the same time. Under the condition 0 < r < 0.9, the result is shown in Figure 4.2.2. Recently, willow has received a lot of attention as an energy source, and it may be planted in the field as an agricultural crop (Eriksson, 2008, Heller et al., The lower panel shows the optimal allocation areas and the number of cows when r is changed.