Solutions :
If the prices are 110€/t for wheat, 210€/t for rapeseed, 85€/t for spring barley and 70€/t for winter barley, the gross margins obtained are therefore as follows :
| Crop | Intensive | Sustainable | Integrated pest management | cropping system |
| bleD | 148.8 | 170 | 181 | 206 |
| colza | -73 | -26 | -23.7 | 17 |
| orgeP | -135.9 | -149 | -118 | -103.5 |
| orgeH | -246 | -190 | -139 | -132 |
If the prices are 230€/t for wheat, 400€/t for rapeseed, 195€/t for spring barley and 160€/t for winter barley, the gross margins obtained are therefore as follows :
| Crop | Intensive | Sustainable | Integrated pest management | Cropping system |
| bleD | 1022.4 | 1022 | 961 | 998 |
| colza | 516 | 525 | 476 | 511 |
| orgeP | 552.7 | 533 | 498 | 523.5 |
| orgeH | 393 | 440 | 437 | 453 |
Prices have no impact on rotations, they remain the same. Rotations follow agronomic rules. However, the prices change the cropping patterns and in this case the cropping system.
With a price decrease, the farmer chooses to cultivate 33.33 ha of rapeseed, 25 ha of soft wheat and winter barley, and 16.67 ha of hemp in an “integrated pest management” system. The farmer’s income is 2112.5€.
With a price increase, the farmer chooses to cultivate 33.33 ha of rapeseed, soft wheat and winter barley in an intensive system. The farmer’s income is 69703.3€.
You can download the solution, check that you wrote the model correctly and obtained the same solution : modelEco_ParisBasin_rotation_price.gms
