The Limiting Factors
Liebig’s Law of Minimum says that the most limiting factor determines the rate of growth. In greenhouse horticulture,Liebig's law has a significant impact of the entire commercial operation. A greenhouse allows us to control the limiting factors of crop growth and thus enhancing production.
To control the greenhouse climate, it is of great importance that all the climatic factors are synchronized. As you can read in the previous post about photosynthesis in greenhouses, the main factors affecting the rate of photosynthesis are light intensity, CO2 concentration and temperature. One of these climate conditions in the greenhouse may become a limiting factor in any given situation.
A plant takes in a lot of CO2 under influence of light. On a darker day, the CO2 intake is low, dosing much CO2 in such situation will not be beneficial and is just a waste of energy and money.
On an overcast day, a high temperature isn’t much preferable. The plant wants to grow due to the higher temperature in the greenhouse. Without much light available, sugars aren’t made in sufficient amounts to keep of with the drive to grow from the plant. This results into a feeble, long crop.
In both examples light is the limiting factor. With more light, the photosynthesis occurs faster. In Dutch conditions, light is often the limiting factor. Due to this, the climate regulation systems in Dutch greenhouses are often subjected to the amount of light. With a lot of light available, the temperature may go up. On darker days, a lower temperature is desired. This is also the case with the CO2 concentration in the greenhouse.
Another reason why the temperature and CO2 concentrations are subjected to the amount of light available, is because the amount of light entering the greenhouse light (in most cases) cannot be controlled. Only with really high amounts and really low amounts, light can be influenced; respectively screening and supplemental lighting.
In most cases the grower will try to have the photosynthesis occur as fast as possible. The temperature, carbon dioxide levels and light are therefore the growers’ most important tools.