In Ireland many growers are now switching over to phase 3 compost in bulk. Especially the growers who have put more shelves in their houses and are switching over to bulk compost, they have to switch over to a new way of growing.
It is now very common to see shelving that goes as high as 4 or 5, and 3 rows of 3 shelves are not rare anymore. But as summer approaches growers have to watch a few things very carefully. Especially filling and casing.
Being present at filling is, for the grower, one of the most important things. At that moment he can judge the compost and try to predict what this batch of compost is going to do.
It is always a matter of feeling, looking and smelling, as the final analyses mostly come a day later.
Phase 3 compost will always go up in temperature after filling. Even if it looks pretty tame. Therefore a good judgement of the compost at filling is necessary.
If the compost looks dry, light in colour and if the structure is long, a rapid increase in temperature can be expected. This type of compost can therefore be pressed pretty hard and if the compost is good and free of competitor moulds, (e.g. green moulds) some water may already be added at filling through the fillinghead.
The limit in this watering should be kept at 7 litres per m² to be safe. This water will not be absorbed by the compost and is given with the intention to lose it again by means of cooling. Contrary to what everyone expects, this watering will however first result in an extra rise in temperature of the compost within 12 hours after filling. But this rise will be easier to control because of the evaporating water.
A dark and short compost with a higher moisture than 66% however should never be watered at filling.
A dark compost will absorb the water and this will lead to a negative result. The filling itself has to be as evenly as possible. This means that the filling head should never stop and that the winch and machine have to run at the same speed. If the machine does not stop filling, the layer of compost will be of an even depth and this is more an assurance to keep the same temperature throughout the house.
The best way of cooling the compost is to case it straight away. There has been great discussion in the last half a year about casing, but what a phase 3 compost really needs is a heavy but open casing soil. This means a casing soil with a high water retaining capacity and with enough structure. Just heavy is not enough.
A heavy casing soil can still be of a too fine structure. A simple test will help to determine if the casing is good. Take a handful and squeeze. If the casing soil completely comes through between the fingers, there is not enough fibre. The compost should then be cased with 4.5 to 5.5 cm of casing soil. More casing soil mostly has a negative effect but a shallower layer does not retain enough water for later flushes.
Straight after casing the house the watering should begin and in first 24 hours the casing layer should be saturated with water. If the compost already had water at the beginning, just touching the compost with water is enough.
If the compost is dry and it did not have water yet, a total gift of water within 24 hours of about 10 litres is what the casing should be able to handle.
The second day most of the time 2 litres is enough, just to keep up with evaporation. Then from day three about 6 litres is needed, declining to 2 litres on the day before recovery or deep ruffle.
If the compost is judged light, dry and long, the grower should not wait with cooling till the compost reaches 25º C, he should start sooner.
If the compost has hit 25º C fast and without cooling, you might be too late to cool it down again. If these measures do not have the desired effect, one can always go to pre-cooling the house before filling.
Flood the house with water, put on the cooling and keep it closed till the moment of filling. After filling and casing, close the doors as soon as possible.
In other words, do not take your tea before the house is sealed up again.
