Use the ‘propagation recipe’ for wetting the germination plugs to full saturation.
Because of hygienic reasons the overhead irrigation is recommended. The “dipping” method must be avoided, because of risk for infection and/or contamination.
Approximately twice the content of rockwool in feed solution is needed for full saturation!
Next step is seeding and covering with vermiculite.
Germination process needs good moisture, oxygen and temperature level. Optimal germination temperature for tomato, sweet pepper and cucumber is 26 oC. Minimum and maximum temperatures are 24o to 28°C. Check temperature at seed level several times per day until appearance of young plants!
Avoid overheating from direct sunlight during germination of the seeds!
If needed, cover the plugs after sowing with polystyrene plates. Not only to avoid too high temperature during sunny moments, but also for a better control of the temperature of the plugs at night. Covering with polystyrene plates avoids de-hydration and ‘salt’ accumulation of plugs.
Wetting and flushing of rockwool blocks
For good possibility of wetting and flushing the blocks they must stay on top of a foil covered soil or concrete floor in a slight slope of about 0.5 %. This is very important to get good drain runoff to a drain gutter at the lowest place.
Blocks can also be placed on a profiled bottom with holes for drain runoff below the bottom. Important is to pay good attention for free flow of drain-water, in order to avoid ‘stagnant’ water.
Uniform wetting and draining are keys for uniform growing conditions of plants.
Before seeding or transplanting seedlings into blocks, they must be wetted and flushed with propagation solution according to the ‘wetting recipe’.
A standard block (10x10x6,5 cm) contains 650 ml and there are 100 blocks per m2 in the first stage of propagation. Dose about1500 ml per block (=150 liter/m2) for uniform wetting and flushing. Do this by overhead irrigation with a uniform dosing system!
‘Dipping‘ method to wet the blocks is not the most optimal method. First the dipping method has a risk of contamination with diseases. Second the good flushing out of blocks is needed to get the right EC and pH in the blocks. These must be similar to the feed solution for seeding cucumbers and/or transplanting seedlings. With ‘dipping’ the blocks they are only wetted, but not flushed!
Check the EC and pH value during the wetting frequently! Measure what goes into the block and measure what comes out after recommended flushing of the blocks. The water content in the blocks, after drain run out stops, will be about 80 % (= 520ml).
Check wetness during the wetting several times with a scale (accuracy of 1 gram). The weight must be approx 570 g for a full saturated block. After good wetting and flushing all blocks have almost the same weight. Not uniform wetness causes problems later on by making choice for best moment of water supply during the whole propagation period! That also leads to differences in plant size, which continues after planting.
Growing uniform plants starts with good results in propagation.