Arboriculture: La Pugère

Experimental system over apple trees in the field station of La Pugère

The field station of La Pugère has been located in Mallemort since 1988 on lands provided by the Conseil Général des Bouches-du Rhône. It lies in the Durance valley, at the heart of the main production area of apples and pears in France.

The region

“In France, the apple industry represents 3 942 farms i.e. 37 296 hectares (96 160 acres) total which corresponds to about 30% of the total farming surface dedicated to orchards in France in 2013. Beyond the significant economic aspect, the apple is a benchmark in genetics as it is the model plant for the family Roasaceae.

At the national level, apple-growing represents 26% of areas in production with a reduction of 4% of the surfaces which has had no impact on production.

43% of the French production of table apples goes to the French market, 38% is exported and the rest is transformed.”

Climate change effects

  • The unprecedented combination of adverse weather conditions (frost, high temperatures and rainfall) during the most important phases of the trees’ annual cycle (from bloom to fruits) results in very high production losses,
  • Some species, such as apple trees, do not cope well with lack of water and high temperatures. Outside their comfort zone, the yield and size of the fruits are dropping,
  • Beyond a given threshold, the consequence of a particularly high light intensity will be photo-inhibition which thus will lead to a reduction of net photosynthesis,
  • The water status plays a major part in vegetative growth. A study of Pink Lady apples which suffered from drought showed an 80% decrease of the leaves and branches biomass compared to reference trees.

Objectives of the agrivoltaic system

The idea is to adjust shade over the crop through mobile photovoltaic panels fitted on trackers, according to the physiological needs of plants. This is controlled by algorithms putting crop production before photovoltaic production.

To do this we will need to:

  • Understand in details the eco-physiology of Golden apple trees under dynamic shade,
  • Develop and test a growth model for apple trees which integrates the impact of shade linked to the agrivoltaic system,
  • Test panel control algorithms, while trying to extrapolate to other crops using a generic approach,
  • Test net systems used in agriculture (anti-hail, insect proof and others) in order to increase the advantages of dynamic agrivoltaic for the farmer and to protect crops more efficiently against increasingly recurring climate events,
  • Measure biomass produced as well as yield and quality of fruits compared to their benchmark solutions.

Information on the experimental equipment

730 m²

under the dynamic agrivoltaic system

300 m²

of control zone

196

pannels

4,5 m

Structure heights

1666 trees/Ha

Number of trees/Ha

1,5 m

Distance between trees

4 m

Distance between rows

61 kWc

Electric Power

The agronomic results

– The water stress level of the trees sheltered by the dynamic agrivoltaic system was 63% lower than the other trees in the control area,
Cooler temperatures were maintained, with decreases ranging from 2 to 4°C.