Update model to suit scientific findings

[tomsaleeba]

Lucerne see 8% extra yield (?) where it borders on reveg and that tapers off linearly to 0% at 200m.

8% |\
   | \
   |  \
0% |   \
   -----------
   0   200m

Apples see a peak in symmetry (an index value) at 10-20% native reveg. This graph is terrible but the I represent error bars and 20-30 is slightly better than 0-10 but we can't get that granularity in this graph. Just know that 10-20% is the best.

     | 
sym  |       I
     | I             I
     |    
     -----------
      0-10  10-20  20-30
          % native reveg

Canola doesn't see an increase in yield, but instead an increase in quality. The benefit is in synchronicity; all the seeds ripening at the same time, so there are fewer green seeds and therefore better oil. The graph looks like lucerne but with 10% at 0m and still down to 0% at 200m.