Fertilization in Greenhouses: an Introduction

Nutritional problems are among the most common problems in greenhouses and can lead to serious economic losses. Plant growth can be reduced if plants get too little or too much of certain nutrients. Even the wrong balance among nutrients can cause serious problems. By the time that deficiency or toxicity symptoms appear, plant growth often is severely compromised and correction of the problems can be difficult and time-consuming. Suboptimal nutrition may even reduce plant growth without ever causing any visible symptoms!

Since prevention is better than correction, it is important to keep close track of your fertilization program. However, there are lots of confusing terms, such as electrical conductivity, pH, alkalinity, and fertilizer acidity. This page has links to several pages that will explain the basics of fertilization and plant nutrition. In addition, there is information on how to make sure that your fertilizer injector is working well. Without an accurate fertilizer injector, it may be very difficult to make sure that your plants get the nutrition they need. In addition, there is software that will help you make sure that your injector is providing the fertilizer concentrations you need.

Click on the following links for more information (Some of these links are PDF files, so you will need Acrobat Reader to open them):

EC and pH: what are they and why do they matter? All the basic information about pH and electrical conductivity a grower needs to maintain good fertility levels in the growing medium.

Testing the Waters Water qualilty can greatly affect the growth of a crop and may affect how you should fertilize your plants. Testing your irrigation water on a regular basis will give you crucial information about how your water may be affecting your crops. Unfortunately, water quality terminology can be very confusing.
Do you understand what pH, alkalinity, hardness, carbonates, and salinity refer to? For a primer on this terminology and related water issues, this summary is a must.

Different methods to measure the EC of your growing medium are described in this reprint from GMPro.

Are your plants on the right diet?
Basic information about greenhouse fertilization programs.

The basics of fertilizer injector maintenance . Everything you need to know to keep your injector working smoothly.

Nutrition Guidelines for Bedding Plants . Guidelines for fertilization of a variety of bedding plants in subirrigation systems.

Excel spreadsheet for some basic fertilizer calculations

This software was developed to help with some of the most basic fertilizer calculations. It has the following three functions:

  1. Calculate the amount of fertilizer to use when you are mixing stock solutions for use with a fertilizer injector
  2. Determine the nitrogen concentration of a fertilizer solution, based on its electrical conductivity
  3. Calculate what the electrical conductivity of your fertilizer solution should be, based on the desired nitrogen concentration of the fertilizer

This software in the format of an Excel spreadsheet and can be downloaded for your use. The file should be opened as a ‘read-only’ file. This assures that there will be no unwanted changes in the spreadsheet. Although I have tried to make sure that all calculations in this spreadsheet are correct, I cannot accept any liability for possible errors. So please use this software at your own risk and if you find any errors, please contact me.

Click here to download fertilizer software