Fertilization during winter

Effect of increasing EC on micro elements, EC in substrate and N / K in winter

Introduction

The dark days of the year start to have their influence on the plants. Less light means less growth and the plant development is slower. The evaporation of the plants increases because of the heating.

Fruit vegetable and micro elements

When the young plants are planted the EC is high to avoid stretching and to get the plant more generative. The EC is increased by increasing the feeding EC, this means that also the micro elements increase in the same amount as the main elements. A feeding tank calculated at an EC of 3.0 and used to create an EC of 6.0 in the slab also means a double amount of micro elements.
The analyses of drain water in winter time often show high amounts of micro elements. Some of the elements are easily taken up by the plants others less, for instance zinc, and this concentration can increase in the slab. Too much micro elements can cause an excess.
When preparing the stock solutions it is important to have a look at the last analysis results. Keep in mind that the EC increase also means increase of all micro elements and this is not always necessary.

EC in the substrate

When pot plants grow in an ebb flood system the EC in the top layer of the pot is much higher than in the middle or bottom layer. The EC in the middle of the pot is approximately 0.6-0.8, on the surface the EC can increase to 3.0-5.0. Cut flowers on substrate can show a similar pattern. Under drippers the water flow is higher and the EC is lower, in between the drippers the slab dries up every time and the salts remain. To avoid this raining from above with clean water is advised. Another option is to give once in a while when the weather is good a higher dosage of clean water with the drippers or ebb flood. In this way some of the salts are dissolved and redistributed in the pot or substrate.
It is also important to lower the feeding EC in time to be sure that the plants have time to take up the surplus of elements before growth slows down.
This will also help in avoiding a too quick increase of the EC in the pot.

Nitrogen en potassium

In summer time more water is given and so also more fertilizers. The uptake of fertilizers is normally correlated with the uptake of water. An exception is periods of hot weather, than the EC is lowered.
This is for instance automatically done in fruit vegetables, depending on the radiation the EC is lowered during the midday hours with 0.2-0.5 EC.
Because of the high gift of water also the gift of N and K are high. These elements are taken up very easy and this can cause a lower uptake of other elements. For this reason the amount of N and K is sometimes reduced in summer time. In winter it is the other way around. The gift of water is lower and this means less N and K in the pot. The plant takes up the elements easily and has to wait till the next watering. In the analyses it is possible that N and K are a bit lower than expected.
In winter time, or periods of slower growth, the feeding has to be done more precise because it is already a more difficult time for the plant and recovering is slower.

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