ReduFuse IR helps tomatoes get through hot summers
After a few years of experience with ReduFuse, tomato grower Prima Fruit switched to ReduFuse IR. This coating combines optimal light distribution with heat shielding in Slovakia’s harsh land climate.
Prima Fruit, where Krisztián Kovács is the grower, is part of the GreenCoop cooperative. Since 2006 the member companies have started developing into a major player. Their domestic market share in tomatoes has meanwhile reached 50%. The GreenCoop sales office is located in south east Slovakia, near the Danube river. At the other side of the river is Hungary, a highly interesting sales market. “We meanwhile have a combined area of 20 hectares under glass, and we are about to expand, says Kovács.
Prima Fruit has 6 hectares of greenhouses with vine tomatoes and plum tomatoes. It is an art to get the crops through summer in good shape. “We have a very challenging climate in this region. In the summer, the temperature reaches 32 to 35 °C or even higher, cooling down to some 20 °C at night. Such conditions result in a series of issues in tomatoes: tip rot, thin heads, double vines, leaf on the vines. All of those are undesired properties that seriously hamper the quality and marketability”, he says.
Optimal light distribution
This means an intervention is needed to keep the problems in check. As long as possible, the grower does not want to reduce the light, but manage the light. “We previously used ReduFuse for that purpose. This ensures a good distribution of the sunlight. It prevents intermittent shadowed and bright sunny patches in the greenhouse. After all, it is the sunny spots that cause light stress. Furthermore, the diffuse light also reaches the bottom leaves of the crop, helping them contribute to assimilation”, says the grower.
The experiences with ReduFuse were good, but it was not enough: “You still need to do something about the heat. This is why we have applied SprayChalk over the ReduFuse at some point. Unfortunately, that cost us a lot of light”, says Kovács.
However, there is a way to postpone the moment of actual light shielding: you can use a different Mardenkro coating called ReduFuse IR. This coating shields the crop from most of the sun’s infrared radiation, as it is specifically the infrared that makes the crop heat up. Additionally, the grower can use this solution to still benefit from the advantages of diffuse light.
“At the advice of Jelle Hoogland, our Mardenkro account manager, we switched to ReduFuse IR three years ago. We can see that the plants are better balanced with this coating. Previously, with high heat, the stems were very thin and weak. With ReduFuse IR, this has significantly improved. We do not use mobile shading; the coatings are sufficient in the spring. However, the conditions are a factor in our variety selection: strongly generative varieties are no match for our summers.”
This year, he applied ReduFuse IR in early May over the sensitive cherry tomatoes. The vine tomatoes were covered one week later. This was later than usual due to the relative overcast spring. In previous years, he was coating as early as April. Depending on the weather, he decides when to remove the coating. This is generally in mid-August, when more rain can be expected.
In mid-summer, extra protection with spray chalk is necessary. This is usually applied once, on top of ReduFuse IR. The chalk film gradually reduces in the course of the summer due to rainfall.
The other GreenCoop companies use ReduFuse or ReduFuse IR, combined with spray chalk in summer. The choice of the coating type depends on the crop type (tomato or cucumber) and the variety or fruit type.
Diffuse light is always beneficial
Diffuse light increases both production and quality for virtually all crops. This is due to two factors: more efficient distribution of light, allowing for a higher total of photosynthesis, and reduction of light stress. Under a diffuse coating, the sunlight is better distributed horizontally as well as vertically. There are no more light and dark areas in the greenhouse.
Under a diffuse coating, the top leaves receive less light and the leaves at the bottom receive a little more. The top leaves are generally already at maximum photosynthesis capacity. So it is fine to give them a little less. The leaves in the middle and bottom of the crop can really use the extra light: they are contributing more to sugar production. The overall result is higher production.
Another key factor is that the diffuse coatings ReduFuse IR and ReduFuse prevent bright sunny areas. These areas are specifically challenging to the crop. The leaves temporary close down photosynthesis in such spots. It can take up to a quarter of an hour before photosynthesis starts up again after the sunny patch has disappeared.
Things are also different when a crop is exposed to heat. The crop can deal with the light level, but is suffering from heat stress as leaf temperatures are running up too high. This gives rise to free radicals that damage a range of organelles in the cells. This primarily leads to reduced quality and eventually to permanent damage to the crop. In such cases, it is important to shield the crop against the heat radiation of the sun. This is where ReduFuse IR comes in. Just like ReduHeat, this coating selectively reflects part of the solar spectrum, i.e. infrared. This part of the sunlight is not required for photosynthesis, but causes the plant and greenhouse to heat up. By shielding the plants from infrared, ReduFuse IR ensures that a high diffuse light level remains available for production.
The experience of the GreenCoop growers set out above shows the benefits. In a hot climate, they can keep both their production and quality at a high level much longer than without the advanced ReduSystems coatings.
Proper functioning of stomata is crucial
The plant is continuously seeking a balance between transpiration (loss of moisture) and photosynthesis. The functioning of the stomata plays an important role in this. Moderate climate conditions are best for achieving this.
Haze factor mainly dependent on thickness of coating
Diffuse glass has a fixed haze factor. If you choose a diffuse coating it is possible to change the amount of light scatter, and hence haze, each year.