Author: Mr. Guy Sela, CEO of SMART! Fertilizer Management software and an international expert in plant nutrition and irrigation.
Growing in nutrient solutions, allow the crop to develop in a sterile environment and liberate the grower from many soil cultivation practices such as mulching, tilling, and weeding.
The main advantage of closed hydroponic systems, in comparison with open systems, is their efficiency in water & nutrient usage.
However, the circulation of the nutrient solution and the constant interaction with the roots, means that the plants are developing in an ever changing environment.
The nutrient solution, has a limited buffering capability, in comparison with soil cultivation. The rapid change in the root environment can have dramatic effects on the crop.
In closed hydroponic systems, the nutrient solution circulation emphasizes the risk of harming the crop. Therefore, the technique demands that the grower will keep close attention to various parameters.
Raw water assessment - Testing the raw water composition in crucial. The results will play a major role in determine the initial amount of fertilizers to apply in the system. Furthermore, the presents of unwanted elements indicate the frequency of water treatment and replacement.
If not dealt with correctly, the buildup of elements such as Na, Cl, B, F, will gradually create toxicity problems. With time, the buildup will damage the crop up to the point where the plants can no longer survive in the nutrient solution.
Changes in the Electrical Conductivity - The EC level changes along time and should be tracked frequently. Changes occur since water are taken by the plants, and since some elements, are absorbed by the plants while others aren’t.
Natural processes such as ions releasing by the root system, and other chemical and biological reactions, are all effecting on the EC.
Even if the EC value remains in a desirable range, it cannot indicate on the water mineral composition. In any case, when reaching undesirable levels, the solution should be diluted or replaced.
The optimal pH range - pH level of 5.8 to 6.3 is optimal. In this range, the availability of all vital elements to the plant, is at its peak. On the one hand, reaching the target pH in the nutrient solution obligates the grower to apply acid.
On the other hand, inaccurate application of acid can cause a rapid drop in the solution pH. Even a modest drop, below pH of 5.5, expose the crop to microelements toxicity.
There is a significant fluctuation in the pH level during the day, and therefore, frequent checking in necessary.
In relevance to plants feeding, a main issue that should be attended by the grower is the content and composition of the fertilizers.
For example, when applying nitrogen, the effect of the nitrate: ammonium ratio on the pH level should be taken into consideration.
Nutrient solution composition - In order to maintain an adequate supply of nutrients to the crop, a frequent testing of the nutrient solution composition in required. Imbalanced nutrient solution will harm the plants and will cause an unnecessary waste of resources.
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