Grower Information Dirk

Variety characteristics and commercial experience.

Variety characteristics

• HR: ToMV|Va|Vd|Fol:0,1|For | IR: Ol | Wi
• Flat cluster shape
• Tomatoes attached firmly to the vine
• Average fruit weight 120-140 grams
• Uniform fruit colouring and excellent firmness
• Good green parts which remain fresh for a long time
• Keeps its good quality when infected with the Pepino Mosaic Virus!
• Plant easy to work in
• 'High taste level' in the cluster tomato segment (results from the taste test of PPO Naaldwijk %juice: 39 | brix: 4.6 | taste level: 58)
• Strong setting ability (also under summer conditions and in illuminated cultivation)
• Strong, generative plant habit
• Intermediate resistance (IR) to mildew
• Good early production
• High total yield
  

Commercial experience

This season the area of Dirk will be 150 hectare in Europe. The variety emerged with a high total yield combined with an excellent quality, even when the plant was infected by the Pepino Mosaic Virus. At the companies where was cultivated generative, Dirk was best in balance. Dirk also stands out for its high yield, good quality and low labour input requirement on these companies.

Plant propagation:
Dirk does not need special treatment. However, some points should be kept in mind. Dirk has a strong, vigorous plant. In trays and when raising the plant, Dirk is more likely to stretch. Illumination may be used depending on the planting period and the wishes of the grower.

Start of the cultivation:
Dirk results in a nice, uniform plant. Therefore, the greenhouses may be heated as usual from the start. However, a D/N difference should be applied fairly quickly. Moving screens and fixed screens are often used nowadays. Using these kinds of screens needs special attention. In mild and dark conditions outside, if possible, the screen is to be opened soon to avoid limp and stretched plants. When a fixed screen is used Dirk will make rapidly length. Keep this in mind when establishing the temperature, fertilizing (a higher EC value is needed) and deciding when to remove the fixed film. Compared to most varieties, Dirk can be moved to the planting hole later than usual (1-2 more flowers in blossom). This will result in a generative crop.
Dirk has a characteristically strong, generative plant habit. Therefore, we expect Dirk to be cultivated rather soon. However, a higher plant load and/or low light conditions require immediate action to remain a good plant head. As a general guideline, we expect that by following a generative growing regime (temperature, EC, CO2) the best results can be achieved with our new hybrid Dirk.

Strengthen clusters by climate/bracing/damaging/pruning/fertilizing:
There is no common advice to strengthen clusters. Dirk has a vigorous plant with a cluster stem of average length. Therefore, our advice is as follows:

• Climate
  In case of grafted plants, a night temperature of 17 degrees is usually sufficient. Non-grafted plants require between 17.5 and 18 degrees. If the plant is warmed up at night, the temperature after sunrise can be lowered in order to strengthen the clusters in the head. Do not overdo this, because if the ambient temperature falls too much, you increase the chance of cold plant heads. Depending on the outside temperature, the aeration temperature can be lowered by 0.5 to 0.8 degree. Thereafter, increase the established temperature in proportion to the quantity of light. The humidity content should not be too high during the day, especially not when grafted plants are concerned. This is how to achieve strong clusters that do not bend too readily.
  It will be good to apprehend the day temperature longer (at nice weather) if the crop is (too) vigour. This can be done till sunset or till ½ hour after sunset. This achieves the balance in the plant again.
  During the months April until September a pipe temperature of 50 degrees during 3 hours instead of a pipe temperature of 40 degrees during 4 hours for heating at night/in the morning is preferred.

• Bracing/cluster damage
  The trusses ought to be braced or nicked for as long as possible (when sowing November 10: the first 5 clusters; when sowing October 25: the first 7-9 clusters).

• Cluster pruning
  Until February 15, you are advised to prune the clusters to 5 fruits. Subsequently, until July 1, prune the clusters to 6 fruits and from July 1 on, again to 5 fruits a cluster. The last 3 trusses must be pruned on 6 again.

• Fertilization
  Dirk may develop clusters that bend and may end up either on or between the leaves, especially when the bracing and damaging activities have been terminated. Consequently, clusters may tear off during leaf picking or cutting. A higher target value of the trace element Boron in March through May will prevent clusters to tear off. We advise 250 micromol/ltr. instead of 70 micromol/ltr. (the usual target value in fertilizer schemes) in the slab.

Working the crop:
Dirk has a plant that is easy to work in and therefore, this variety does require hardly to any special treatment. In spring and autumn, extra leaves in the head may be removed. This may also be required to create enough room for extra side shoots in spring. Make sure that growing side shoots will not be at the expense of the stem density. It may be necessary to have the side shoots grow later in the period, especially when grafted plants are concerned. Sometimes, it is best to grow them in two phases. A stem density of 3.3 stems/m2 is sufficient during summer. In case of non-grafted plants, 3.7 stems/m2 may also be an option. To avoid Botrytis it’s the best to cut the leaves from the plant.

Plant type:
Dirk has excellent results regarding early production and the total yield is very high. The length of the crop and the leaves are normal and the leaves are fairly broad and well filled. Dirk's staying power is excellent. Moreover, this variety is intermediate resistant to mildew, making fumigation unnecessary.

Quality:
The clusters of Dirk are nicely fishbone shaped and the fruits are well shaped with a nice, uniform fruit colouring. The green fruit of Dirk is a bit paler. The fruits may be of a lighter red colour, especially in summer and late summer. A low K-value and a dense crop result in this light fruit colour. Therefore, ensure a good K-value and make sure the plant remains sufficiently open.