Determining minimal-necessary irrigation in apple orchards by water and carbon balance characterisation
Our general objective is to determine minimal necessary irrigation in apple orchards, by including the interdependency of water and carbon balance. To achieve this goal, the MaluSim model has been selected. First of all it has to be parameterised to Mid-European tree characteristics and cultural conditions. This includes adaptation to apple varieties in Europe and to European growing systems. Thereafter current knowledge and data of our experiments shall be used to identify how water influences productivity of apples and to include a water submodel into MaluSim.
Background: Until today irrigation in Germany is only applied as an additional irrigation, because in most regions precipitation is sufficient. With regard to worldwide climate change and the predictions that in many regions the dry periods will increase the relevance of irrigation increases. Irrigation also gives the opportunity to control and optimise plant development. For this the main question is:
When and how much water should be applied to the trees?
To answer this and other questions concerning water balance of apple trees we use the carbon balance model MaluSim (Lakso, 1992; Lakso, Greene, & Palmer, 2006; Lakso, White, & Tustin, 2001) and additionally conduct experiments in apple orchards. For the experiments we chose 3 different cultivars (small, medium, & big sized fruit) and have different irrigation regimes. Among other measurements we do sap flow measurements (see picture), determine photosynthetic rates, and observe soil moisture with different sensors. An additional aim is to check if MaluSim is able to predict natural fruit drop. This information could then be used to give advices for chemical thinning of apples.
Objectives : Parameterisation of MaluSim for Germany
- Check if MaluSim has to consider apple variety
- Development of a water-submodel for MaluSim: main aspect is to describe effects of waterstress on productivity of trees. Most important is how photosynthesis is affected
- Predict natural fruit drop and give advices for chemical thinning
