Page 18 - Griffin Gazette Q3 2017
P. 18

Soil pH is critically important to plant
                             health. The availability of most nutrients is
                             influenced by soil pH. The ideal pH range
                             for greenhouse and nursery crops can vary
                             substantially, based on the unique nutrient
                             requirements of each crop. Some crops are
                             very efficient at taking up micronutrients
                             from the soil, so much so that a lower-than-
                             ideal soil pH may lead to a micronutrient
                             toxicity. Zonal geraniums, New Guinea
                             impatiens, pentas and African marigolds are
examples of this effect. As soil pH climbs above 6.0, micronutrient
availability decreases and can lead to micronutrient deficiencies in
many crops. Iron deficiency, for example, is often seen in spring
crops such as calibrachoas, pansies, petunias and many others.
The development of certain soil-borne diseases are influenced by
soil pH as well.

Given the importance of soil pH, it would be great if growers could
just "set it and forget it." Unfortunately, so many forces are acting
on the pH of the soil that it's just not possible. Let’s consider some
of the factors that making frequent monitoring of soil pH necessary:

•	Growing mixes can arrive with widely varying soil pH values.
Many soil mix companies state a starting pH range of 5.5-6.5.
For some crops pH adjustments will need to be made right away.
Petunias started at 6.5 will not make optimum growth for example.

•	Water quality will also influence soil pH. Low-alkalinity water
sources provide little or no buffering capacity (i.e., resistance to
pH change). This can lead to rapid soil pH swings. High-alkalinity
water sources may lead to increasing soil pH over time if the excess
alkalinity isn't neutralized.

•	 Fertilizer selection needs to be considered in concert with the
alkalinity of the water and the pH requirements of the crops being
produced. Some fertilizers are basic in soil reaction, others are
acidic. GGSPro can help you build a fertilizer program that takes all
of these factors into account.

•	 Last but not least, there is a phenomena sometimes referred to
as the “species effect’. Many crops will influence the pH of the soil
they are planted in and not always in the direction that would be in
their favor. For example, flowering vinca exerts upward pressure on
soil pH in spite of the fact they prefer a lower soil pH.

There are several reliable ways to monitor soil pH. The 2:1 and
pour-thru methods are used effectively by many growers on site.
The digital version of this article will have links to step-by-step
instructions for both methods.

2:1        Pour-thru

Direct-Stick Soil pH Meters

                                                                                                         By Rick Yates, GGSPro Technical Services Manager
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