Water Quality and Fertilization

Water Quality

The PGC water source is from the City of Bozeman 's water treatment plant. The most important parameter of water quality is the alkalinity rating. Alkalinity is the measure of a water's ability to raise growing media pH. The PGC water is in the 100 mg/l CaCO3 range, which is a moderate level of alkalinity. The impact on users is that our water will slowly cause your media pH to raise over time. To counteract this tendency you should select a fertilizer that has a moderate to high level of potential acidity. The PGC office has pH and EC (soluble salts) meters for use. The pH and buffering capacity of the growing media also impacts your fertilizer selection. Some recommended starting points follow.

Fertilizer Recommendations

All high quality greenhouse fertilizer labels have the following information:

• A three number code that list the amount of nitrogen, phosphoric acid, and potash (N-P-K)
• A listing of secondary and trace elements
• Sources of elements – Especially important is the ratio of ammonium nitrogen (acid forming) and nitrate nitrogen (basic)
• Rate and frequency of application information
• Fertilizer solution electrical conductivity table - Allows users to check the function of their fertilizer injectors

Sunshine Mix #1 Users

This peat based media has a pH of 5.9 and requires a fertilizer with moderate potential acidity. A 20-10-10 formulation would be a good starting fertilizer. Pour-through test results performed during the cropping cycle might indicate a need to change formulation to adjust media pH.

MSU Soil Mix Users

This soil based formula has a pH of 6.1, but does not have the buffering capacity of Sunshine Mix #1. Users might consider using a 20-20-20 formulation of fertilizer which has a high potential acidity.

Fertilizer Delivery

The most common method of applying fertilizer is injecting it into the irrigation water.  The PGC will provide you with a "Hozon" bucket injector with a injection ratio of 1:16.  This means you must make a stock solution that is 16 times stronger that the required fertilizer concentration.  The injector is screwed onto the hose bib and the black tubing is placed into your stock solution.  As water passes through the injector it creates a vent uri effect and siphons fertilizer into the water stream.

Return to regular view	Text-only	Updated: 01/10/2006