The effect of different silicon fertilizers on the greenhouse cucumber production

The advantage of silicon for plants is well documented in literature as an improved resistance against fungi, in particular mildew. ELKEM Norway produces a silicon rich material, Solarite, which when present as very fine particles, is readily soluble and can neutralize acidity. In cooperation with Jiffy Norway Solarite was added to peat slabs. Common rockwool was added as a reference treatment. A mildew tolerant and a mildew sensitive variety of cucumber were planted on various slab types. Solarite resulted in a level of silicon of 0.5 mmol in the 1:1.5 extract. This resulted in a reduced incidence of naturally occurring mildew of 26% of the reference. The mildew tolerant variety showed less than 5% of mildew incidence. The silicon levels in the 1:1.5 extract reached with a common silicon source, micro crystalline silicon, were 0.2 mmol.l-1 and resulted in a mildew incidence of 63% of the reference. As reported by others, we found a yield reduction of 5% due to the use of silicon. In conclusion Solarite is an effective way to raise the silicon content and reduce mildew incidence in mildew sensitive higher yielding varieties. This must be traded off against the convenience of mildew resistant lower yielding varieties.