Articles
RAIN COVER PROTECTION AGAINST CRACKING FOR SWEET CHERRY ORCHARDS
During the ripening season (July 1 – August 15), the precipitation in the main sweet cherry growing area in western Norway is on an average 100 mm.
Tree covers which are wind stable and economically feasible are a demand from the fruit growers.
At Ullensvang Research Centre, research has been conducted to improve the present rain cover.
So far, the most common construction has been the "one-wire system" consisting of wooden poles spaced about 12 m apart in the row and a high tensile wire on top of these poles.
The top wire supports rectangular polyethylene sheets, with lengths similar to the pole spacing and width like the row spacing.
The sheets are tied with ropes to the trees in the row beside.
These ropes are obstacles for a tractor operating in the alleyways.
A more advanced construction is the "three-wires system". In addition to the top wire this system has two side wires positioned about 0.5 m lower and 2.0 m from and parallelly to the top wire on each side.
The side wires are supported by transverse wood work or strong wires connected to the poles.
The polyethylene sheets are supported by the top wire and connected to the side wires with elastic rubber bands and snap hooks.
The hooks can slide back and forth on the side wires so that the polyethylene sheets can be operated like a curtain.
The sheets are stretched out when rain is expected and pulled together in sunny periods or during heavy wind to protect the system against damage.
Tree heights are limited to 3.5 m and the tree row distance to 4–5 m.
The system allows compact tractors to operate in the alleyways.
This system is designed for high density sweet cherry orchards producing for the domestic and export market and is currently chosen by most Norwegian growers.
The "three-wires system" will be further improved.
The work is mainly aimed at developing a stronger and more flexible connection between sheets and wires.
Better sheets which combine strength, low weight and acceptable price are also wanted.