The cultivation of apples in soilless trenches already produces higher yields than regular orchards. This cultivation system is also more sustainable, because it requires less chemical plant protection products to achieve healthy yields.
These are some of the results of research conducted by the Bulbs, Trees & Fruit business unit of Wageningen University & Research. In a trial in Randwijk, the cultivar Junami produced more in the trenches than in most of the traditional orchard plots after the sixth year of cultivation (2016). If the Junami trees in trenches can maintain the same level of production for 12 years, the cultivation of Junami in trenches will probably become even more profitable than traditional orchard cultivation of the cultivar Elstar.
Improved control of cultivation conditions
The system of cultivating apples and pears in soilless trenches instead of regular orchards was originally developed to make it profitable to grow these trees on sandy and clayey soils. Improved control of fruit growth, yield, size and quality by means of fertigation (applying artificial fertiliser with drip systems) leads to both a higher quality product and less pollution. The narrow and shallow trenches are lined with a plastic liner and filled with special sand. In the Randwijk plot, researchers are controlling the conditions for growth in the trenches down to the tiniest details. Water and nutrients are carefully applied in each trench from a central fertiliser room. The water that is discharged from the trench is collected separately to measure the amount of minerals absorbed by the trees.
Soilless trench cultivation in practice
The first trench cultivation trial plot was established in late 2016. In Cothen, researchers are growing 0.5 hectares of pear in trenches. This land has been infected by a honey fungus that spreads by root-to-root contact and cannot be controlled. Soilless trench cultivation is the best way to overcome this problem. The research results suggest that trench cultivation could enable growers to avoid various major soil problems such as diseases and plagues, flooding and salinisation, poor soil structures, etc.
The only question that remains, is whether the trees in trenches will remain vital and productive for a sufficiently long period. Trees in trench cultivation systems only produce 15% of the root volume of ‘normal’ trees in traditional orchards. The Randwijk trench cultivation plot is now six years old and there have been no signs of loss of vitality yet. However, the trees will need to continue to maintain the current production levels for about 12 years if the system is to be profitable in practice (the economic lifetime of a traditional apple orchard is 12 years). An economic assessment will be carried out in 2017.
This research is being funded as part of the Horticulture and Raw Materials ‘Top Sectors’ programme.