EN - iSii, Crop evaporation, how to use Plantvoice

EN - iSii, Crop evaporation, how to use Plantvoice

   
Question

How to use Plantvoice?

 Answer 

A crop loses water and energy due to evaporation. A plant receives energy for crop evaporation through radiation and convection energy.
Radiation comes from the heating tubes and from the sun, and if available from the assimilation lighting. About 50 percent of the tube heating capacity leads to crop evaporation. Convection energy can be contributed through flowing air, that is warmer than the temperature of the crop. For a good balance, the amount of water given during irrigation should at least be as much as the amount of water that evaporates. Not all solar radiation that is measured outside is responsible for crop evaporation. Part of it is intercepted by the greenhouse construction and the roof (glass or plastic) and by measures that have been taken to prevent too intensive irradiation e.g. coating and screens.

The various parameters that influence crop evaporation must be recognized and the specific influence must be familiar to the process computer. The extent to which these determine evaporation must also be made known as a setting. For example, the measured radiation from the sun outside in W/m2 can count as an influence, but also the radiation measured inside the greenhouse with a PAR sensor in micromole/m2.

The iSii has a special Plantvoice setup list. All sources responsible for crop evaporation can be set as influences. In the example below, the following influences apply: radiation through the sun, radiation through the heating tubes, radiation through the assimilation lighting and air circulation through fans.




As an example following influences could be set. These are:

-          PAR measurement in the greenhouse of 2.000 micromole/s/m2 contributes 435 W/m2
-          Tube heating of 80oC contributes 75 W/m2
-          Outside radiation of 1.000 W/m2 contributes 700 W/m2
-          Assimilation lighting contributes at least 80 W/m2 when switched on


The energy required for the evaporation of water can be used as a starting condition for an irrigation cycle.
2.5 Mega Joules are required for the evaporation of 1 liter of water.




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