News
From the Editor: March-April 2019

By now, you may have heard about a book called Plant Empowerment, written by researchers in the Netherlands. It takes a crops-first approach, emphasizing the importance of plant physiology in climate control and greenhouse production practices.

We released a short introduction to it back in January’s Technology Issues feature, where we highlighted some of the key concepts that form the backbone of the book.

Hoping to bring more of these game-changing ideas to you in bite-sized formats, one of the authors, Jan Voogt, has graciously agreed to whittle things down to three or four key topics in multiple, shorter articles. The first starts in this issue.

As some of our readers may know, Albert Grimm of Jeffery’s Greenhouses and industry consultant Dr. Theo Blom used to teach night courses on similar concepts in greenhouse production – something I hope they will take up again in the future. In our conversations, Albert shared some key messages that he’s taught over the years:

1. “We do not heat the greenhouse so that the thermometer reads a given temperature. We heat the greenhouse so that we can supply energy to the nutrient and water transport system of the plants. If we do not supply adequate energy to the plant, the nutrient and water transport system stalls, and our crops experience the floral equivalent of a heart attack.”
2. “… more damage is done to crops by imbalances between root pressure and evaporation than by any other cause.”
3. “There are two components to photosynthesis: a) the plant captures energy from solar radiation [and] b) the plant stores this captured energy for later use in the form of carbohydrates. It is the job of a greenhouse grower to use greenhouse climate and nutrient supply to dictate to the plant when and where to use these carbohydrates. That is the meaning of the term crop-control.”
4. “We cannot change the development of a plant by adding growth factors. We can only prevent [the] development of the plant by restricting specific growth factors until they become the determining limit for plant development. This means that we have to understand how each growth factor impacts the plant… We have to be able to determine which growth factor is most limiting to the development of a plant before we can create a consciously targeted change in plant development. [For instance,] there is no fertilizer that promotes flowering in potted plants. The best that we can do is limit the access to certain nutrients so that the plant uses less carbohydrates (stored energy) for development of leaves. This gives the appearance of larger/more/earlier flowers, because there is comparatively less canopy, but it is merely an appearance.”

As you read through the rest of this issue on irrigation and rootzone management, you’ll find a very prominent theme that resonates throughout – do what keeps the plants happy, not necessarily what makes the grower happy.