Activity 19C : “Paris Basin” model – Regulatory

Length : 40 minutes

You will enrich the model which you wrote in the exercise in Lesson 11 (concerning technologies) and enriched in Lesson 14 (concerning rotations). New data has already been entered into the following model which you can work with : modelEco_ParisBasin_publicpolicies_data.gms.

« The State has implemented environmental regulations for all farms in order to reduce the use of phytosanitary products. It imposes a maximum threshold for the average TIF per hectare on all farms. »

Test various thresholds between 2.5 and 5 IFT/ha.

Questions :

1) What can you say about the results (cropping pattern, income, average TIF) ?
2) Compare the results with those obtained when the State imposes regulations forcing farms to remain under a given threshold. How is it possible to carry out a cost-benefit analysis of the policy ?

Reminder of the problem statement :
« A farmer in the Paris basin has a 100 ha arable crop farm. He can grow soft wheat (cleT), rapeseed, spring barley (orgeP) and winter barley (orgeH). For each crop, he can choose between three management systems :

• Intensive (written « intens ») : it is the most intensive system in terms of chemical inputs. The farmer has a “preventive” use of phytosanitary products. In other words, he does not wait for the appearance of diseases or pests in order to spray.
• Sustainable (written « rais ») : it involves “sustainable” practices. The interventions of the farmer are decided following the observation of diseases or pests in the plot. The quantities used are adapted to the situation.
• Integrated pest management ( written « protI ») : such practices integrate prophylactic agronomic measures which contribute to a decrease in the pressure caused by pests. They can involve considerations concerning sowing dates, variety choices, crop successions in a plot, etc…
• Integrated pest management at cropping system level (written « SystCI ») : this practice was developed in order to control pests and offers agronomic levers at cropping system level, notably with a change in cropping patterns.

The details of the variable costs are known for each management system and each crop : expenses in phytosanitary products (op_phyto), in fertilizer (op_engrais), in seeds (op_sem) and in mechanization (meca_MO) (fuel and depreciation).

The farmer knows the expected yields, the variable costs, and the working time required for each system and each crop.
He can work 2000 hours a year.

The selling prices of crops are as follows : 180€/t for soft wheat, 365€/t for rapeseed, 170€/t for spring barley, 155€/t for winter barley and 320€/t for hemp.

It was observed that farmers used cropping patterns for organisational reasons, by alternating summer crops and winter crops, and for agronomic reasons notably due to the positive effects of a crop on the next one : soil structure and fertility, pest control, etc. But rotations are currently often short (one crop can sometimes be used twice in a row), which leads to the need to increase the inputs in fertilizer and phytosanitary products.

You are going to integrate the rotations into the model.

In the « intensive »  « sustainable » and « integrated pest management » management systems, the rotation must observe the following agronomic rules :
– Oilseed crops cannot be cultivated more than once every three years on the same plot,
– cereal crops cannot be grown two years in a row
– each cereal crop can be cultivated on half the cultivated area dedicated to cereal crops at the most

The final rotation, that of « integrated cropping system » introduces hemp in order to extend the rotation. Longer rotations, which imply that a crop is grown less frequently in the rotation, make it possible to control pests more efficiently. It observes the following rules :
– oilseed crops cannot be cultivated more than once every three years on the same plot,
– cereal crops cannot be grown for more than one year on the same plot
– each cereal crop can be cultivated on half the cultivated area dedicated to cereal crops at the most
– hemp is grown once every six years

An indicator is used in order to calculate the use of phytosanitary products per crop, the Treatment Frequency Index (TFI) per hectare, which combines the number of of spray applications and the doses applied: the more intensive the management system, the higher the index (see table below). Hemp is not treated chemically. Its TFI is therefore always equal to 0. Phytosanitary products are divided into four categories : herbicide (herb), fungicide (fong), insecticide (ins), other.

 The objective of the farmer is to maximize his income. »

Write the model in GAMS and check the answers.