Hop spikes
The chopped guide wires after the hop harvest are called hop spikes (plural only).
root cause
During the hop harvest , the hop vines are removed along with the wires. Then the cones are separated and the unusable plant remains are shredded with the wires in chopping machines. The hop growers then bring these residues onto the fields as fertilizer. Parts of the load can get onto the road.
Every hectare of cultivation area produces around 300 kilograms of metal waste. The 1–2 cm short pieces of hop wire can penetrate tires and lead to a creeping puncture . According to estimates, 2,000 tires are destroyed annually in the Hallertau growing area alone .
Countermeasures
Farmers can counteract the unwanted distribution of these hop spikes by only using closed vehicles or collecting trays. Magnetic collectors are also occasionally used, which collect the hop spikes by driving them over during the harvest season.
A more effective option is to separate the wire pins from the plant residues at the vine chopper. This can be done either by magnetic tapes or drums; the separation rate is around 90%. The sedimentation process is in the testing phase : the metal pins are deposited on the ground in a water basin downstream of the chopper and the remains of the vines are removed with a rake. An efficiency of 86% is achieved.
The most common method to date has been to clean the streets with street sweepers after the hops have been harvested.