Newsletter - Aubergines, Week 7 2010

Maintype	Substrate
Crop	Aubergine
Croptype	Oval
Variety	Gabriella RZ

Newsletter aubergines

Crop tips week 7

At least 50% of aubergine growers are cutting this week or will start cutting next week. At this stage the plants are very quick to show if the fruit load is causing difficulties. But when they do, you are already a day late with cutting. Generally speaking, the flowers have been very keen to set the last couple of days because, on sunny days at the start of this week and in combination with the low outside temperatures, we cannot (or don't want to) realise an afternoon peak of more than 24°C in the glasshouse. We regularly see plants with the 4th fruit already setting and the bottom one still on the plant. These are signs that we do have to take the secateurs to them even though we might prefer to cut them a little larger.

Due to the cold weather we have used hot pipes in recent weeks, so we have not seen any calyx desiccation yet. The calyxes are strong because they have been transpiring copiously and contain, therefore, sufficient dry matter (calcium) and so you don't need to worry, either, that a too high pipe temperature would now cause calyx desiccation. A hot pipe (55°C) during the day is, therefore, absolutely fine in order to create an afternoon peak when radiation is high (>300 W or >500J). The bottom fruit will still fill out well and give the correct weight for cutting the following day. You should preferably not close your thermal screen between 3.00 and 5.00 pm to achieve this goal, for a higher (plant) temperature combined with less radiation on the leaves weakens the plants unnecessarily.

Earlier (in January) we noticed a lot of withered flowers. In most cases it was just the odd flower in a row, but sometimes there were more. It remains important to keep at the back of your mind that Jaylo and Gabriella are light-sensitive varieties, so we have to play into this by keeping things cooler on a dark day. This rule also still applies in February/March. It may be 2 - 4 times as light as in January, but the situation is still the same because the fruit load totally compensates for this.

So on a light day we can use a slight increase for light. The plants will appreciate 23 - 24°C on days like that to get transpiration going and to top up minerals. These are the days when we work on day/night differentials and keep the plants generative. When we get several overcast days in a row we can use a slight pre-midnight drop in temperature or reduce the overall night temperature in order to keep the 24-hour temperature down, increase the differential and so encourage fruit set. The sun does not have much strength yet, so on a sunny day, too, we can drop in good time towards the pre-midnight temperature by means of a limited pipe temperature.

On nurseries where CO₂ dosing is done with the CHP engine only, the pre-midnight can also be used on such an overcast, windless day to do a bit of ventilating (with a closed screen, if necessary) and refresh the glasshouse air that way. However, as long as it is still around freezing during the night it is easier to open the vents slightly during the day when radiation is high. Renewing the glasshouse air once a week is often sufficient.

Those growers who were a little less strict about removing extra flowers are now seeing that most of these have set and the fruit load on these nurseries is rising rapidly (too high >10/m²). The result is that the odd flower on the main stem can wither. Extra fruits generally grow to be slightly smaller, anyway, so this should certainly be borne in mind when it comes to harvesting these aubergines in 2 - 3 weeks' time.

Demo glasshouse
In the demo glasshouse the heart fruits of all varieties have now set and they are starting to fill out very nicely. Development of these aubergines of variety Gabriella is slightly ahead of the other varieties. Crops across the board are a little on the heavy side. The constant air stream caused by the vertical fans which were installed after the crop change-over makes the crop a little more generative and gives thicker stems. That is why a slightly greater day/night differential is used at the moment and the temperature is increased fractionally, to make the crop more generative and faster.

From now on the sideshoots are left to give a higher fruit load which especially the smaller varieties could do with. A small leaf is also taken out of the head, which benefits the balance. Other than that, everything is growing nicely and the crop is lovely and green.

Crop advice, descriptions, recommendations, illustrations and other information, e.g. relating to sowing dates and harvesting dates, given by Rijk Zwaan Nederland B.V. and/or its group companies, in whatever form, are as accurately as possible based on experiences in trials and in practice. Rijk Zwaan Nederland B.V. and its group companies do, nevertheless, not give any guarantee that such information is complete and correct. Rijk Zwaan Nederland B.V. and its group companies do not accept any liability whatsoever for deviating results in the product grown, and to which the information relates. The grower himself is responsible for storing the product correctly and he should judge for himself whether a product is suitable for the intended purpose and the growing conditions that apply.

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