Newsletter tomatoes, loose

Crop tips week 38, 2011

General
The heads have been removed now on virtually all nurseries. The final phase of the crop will consist of working on an adequate fruit size. To achieve this it's best to use a pre-midnight of 14 -15°C, but always ensure that the temperature is back up to around 17.5 - 18°C by sunrise. With the autumnal weather this week 'activity' is definitely the magic word. A lot of crops are quite vegetative at the moment, with long leaves and still giving a robust sideshoot at the top, so allow a lot of light in the crop: just keep on de-leafing and if there are any dead plants remove them now. Light in the crop equals fruit size and activity.

Water and feed
With the recent disappointing weather it has become ever more important to work adequately on root activity. Letting the slabs dry out by 10 - 15% to achieve this is certainly possible. We have noticed that the latest generations of rockwool slabs can go from quite dry to saturation point quite easily, so on dark days we must limit the amount of water we give and keep the watering period very short, i.e. from 10.00 am to 2.00 pm, keeping the run-off limited and the watering rounds generous. This can make the slab-EC rise quite considerably and we do want to give the plant enough 'fresh' feed. In order to achieve this you could, on a day with a reasonable amount of radiation (e.g. >1,000 joules), consciously increase the amount between 10.00 am and 2.00 pm in order to re-adjust the feed in the slab slightly. Do not allow a too low EC in the water (keep it above 3.0), but keep the EC in the substrate stable by allowing a little more run-off.

Screens
Using the screen in autumn has once again been the subject of discussions. Do take care. Freely using the screen too early can cause enormous weakness in the crop and does absolutely nothing for production. Assume that screening is only possible if the temperature set point is achieved with a pipe of at least 35 - 40°C. In that case you can also still do something with ventilation gaps. So in practice it means that screening is only possible to a limited extent - only a little bit during the latter part of the night.

Lastly
We wish everyone a good final push and good luck with your planning for the next growing season. It goes without saying that the Rijk Zwaan crop advisors will be only too pleased to advise you of your options for the coming season.