Fertilizer frequency: Periodic or Constant Liquid Feed?

Hello Jack’s Fertilizer Fan’s — Here is another question that we have been answering quite a bit this season, I hope you find it helpful.

Grower:  “We are currently using your Jack’s Professional 20-10-20 Peat-Lite.  In the past we have continuous fed our annuals that we bring in to sell – however this year, the flowers are just not popping like we would like so we switched our fertilizer frequency and just feed periodically and alternate with clear water. Is this causing us a problem?”

Dr. Cari’s response:

Well yes, we get this question quite a bit especially with growers that are just finishing plants to sell at their own garden centers.  Depending on the water quality of the greenhouse – periodically feeding with a higher rate of fertilizer and and alternating with clear water can cause an imbalance of nutrients in the root zone.  In most cases, a regular cycle that includes clear water  significantly drops the root zone EC – the nutrients that are held in the media – in short, a good drench with clear water often will push out the good and beneficial nutrients that were left by a fertilizer application. This leads to a roller coaster effect with periods of high nutrient concentration in the media followed by periods of very low nutrient in the media – similar to yo-yo dieting.

I would suggest fertilizing with  continuous liquid feed program at a lower rate 150ppm -200 ppm  — this will improve the overall consistency of the plant’s growth.  You will be feeding at a much lower, but what the plants are seeing is a balanced level of nutrition and that will lead to more regular growth patterns in the tissue and flower production.

So how do you figure out if you are using the right fertilizer?  At J.R  Peters, we suggest beginning with a water analysis.  A water test is the foundation for grasping the key components of your water and will help you make the right choice of fertilizers for your plants.    You may be able to get some of this information from your local municipal water company but they most likely will not have some of the key information that you as a grower need.   To get all of the key information you should have your water tested by a reputable testing company that specializes in horticultural or agricultural testing.    Many of the state run universities do this type of testing and certainly there are private companies who specialize in this type of testing.   Our JR PETERS LABORATORY is one them.

Knowing all the components and characteristics of the water being used is key to providing proper nutrition to the plants.   An understanding of one’s water quality and matching a nutritional program to those characteristics is essential.   Too often, growers wait until they see a problem before they fully consider these factors.