From an agricultural point of view, spring is one of the most interesting seasons when it comes to irrigation in this phase of the year in plastic crops. Normally in this phase we are at a time when we either have a recently planted crop, either melon or watermelon or with short cycle courgettes, or we are finishing with long cycle crops of tomato, pepper or aubergine. enriched or in hydroponic cultivationwe are extremely conditioned by the climate. At this stage, we can say that the limiting factor is the climate, and without paying attention to the climate we cannot succeed in any of the above-mentioned crops and growing media.
What are the effects on the climate inside the farm or greenhouse?
The main characteristics of the climate are usually as follows: In the mornings (right at sunrise, around 8:00 am), temperatures are around 10ºC and relative humidity levels are close to 90%. By mid-morning (after 12:00 pm) we can get close to 40ºC. Therefore, we can usually see thermal jumps of + 30ºC approximately from 8:00 am to 12:00 pm.
What happens is that, if the temperature starts to rise quickly, it has a rapid effect on the drop in relative humidity on the farm and this effect will cause a rapid and high transpiration of the crop. Therefore, if we are not attentive and quick with climate management and especially with irrigation, when we go to irrigate, it is possible that the plant already has a stress (at least a generative growth tendency). The end result is a bad development of the plant and problems in the fattening and ripening of the fruit.
How can we respond to changes in temperature and relative humidity?
Ideally, a minimum of technology should be used to help us understand how and when changes are occurring. There are many monitoring systems, but now we will simply focus on explaining how a thermometer on the farm can help us draw positive conclusions.
Using a thermometer, the thing to do is to record the temperatures hour by hour. It is not a question of what is the maximum temperature we reach... What causes stress in the plant is the speed at which we reach that temperature!
We must try to ensure that the temperature in the greenhouse does not exceed 4ºC/hour of thermal jump.. If it does, the plant will be stressed, and we are guaranteed to have the typical problems of over-temperature stress inside the farm or greenhouse.
If the temperature does not exceed 4ºC/hour, something we must also check is the light that enters the farm. In this way, we will ensure that the light the plants receive is correct and therefore we can ensure a good vegetative/generative balance of the crop.
What are the consequences if the plant is stressed by the climate?
- The plant is forced to over-transpire in order to stay hydrated, thus reducing its capacity for proper and optimal photosynthesis, which results in less sugars being generated.
- The plant tends to absorb more chlorine and less nitrogen, resulting in yellowing and thinning and weak heads.
- The higher the temperature, the shorter the maturation and, therefore, fattening time.
- The higher the temperature, the higher the internal conductivity of the plant and therefore the lower the sugar transformation rate.
- If we do not control the relative humidity, strong drops in humidity can occur and this means that the leaf defends itself by sending potassium and sodium to the leaf to help the stoma to defend itself against dehydration. The result is orange ripening in tomatoes and, above all, premature ageing of the leaves.
- Finally, a significant blockage of difficult to move elements such as calcium and iron is observed.
