Length : around 20 minutes
Based on the same case as before, this time 3 rotations have been observed in the practices of the farmers :
- sugar beet/Soft Wheat/Barley/Rapeseed/Soft Wheat/Durum Wheat
- Rapeseed/Soft Wheat/Barley/Potato/Soft Wheat/Durum Wheat
- Rapeseed/Soft Wheat/Barley/Rapeseed/Soft Wheat/Durum Wheat
Write a new model which takes into account these three rotations as activities and recalculate the gross margins and water needs. It is another way to model rotations than those used in Activity A.
“An arable crop farmer growing special crops in the Centre-Val de Loire region (data INOSYS Système GC 131 ) has 110 ha of land. Irrigation and the economic environment of his farm offer him a large range of production options : soft wheat, durum wheat, spring barley, potatoes for human consumption, sugar beets and rapeseed. Five of these crop types are irrigated in order to ensure regular high quality production. The farmer has 60 000 m3 of water.
Irrigation needs and economic data are shown in the table below :
| Irrigation | ||||
| Crops | Volume in m3/ha | |||
| Soft wheat | 175 | |||
| Durum wheat | 350 | |||
| Spring barley | 700 | |||
| Potato for human consumption | 1800 | |||
| sugar beet | 1750 | |||
| Technico-economic situations | ||||
| Crops | Yields (qx/ha) | Prices/qx (€) | Total costs (€/ha) | |
| Soft wheat | 85 | 16 | 460 | |
| Durum wheat | 71 | 28 | 565 | |
| Spring barley | 70 | 17.5 | 470 | |
| Potato for human consumption | 495 | 14 | 4210 | |
| sugar beet | 950 | 2.6 | 1082 | |
| Rapeseed | 40 | 38 | 490 | |
Source : INOSYS network of the agricultural chambers of the Centre Val de Loire region. 2016
What is the optimum cropping pattern for this farmer ? What is his optimum income ?
Compare the solution with the one obtained in the rotation1.gms model.
Then check the solution : 
