| The soil less mixes used by most growers today have many good qualities. Unfortunately they also bring with them a rather low ability to resist pH changes. Understanding the influence of water quality and fertilizers on media is needed to maintain optimal pH values for your crops. The trace element packages in the higher quality water-soluble fertilizers are so good that if we maintain the proper media pH, we can head off most micronutrient problems. It gets a little complicated because crops differ in their ideal pH range, and we are often producing crops with different requirements in the same growing area. |
| Seed and cutting grown geraniums (ivy geraniums excluded), African marigolds and poinsettias are examples of crops that require a higher soil pH range of 6.0-6.5. In the case of poinsettias this range is needed to maximize the availability of molybdenum. Geraniums and African marigolds need a higher soil pH to avoid accumulating damaging levels of iron and manganese. These two micronutrients increase in availability as pH decreases. |
| Petunias, pansies, and mums are examples of crops that require a lower soil pH range of 5.5-6.0. Each of these plants needs plenty of iron to avoid intervienal chlorosis of the upper foliage. Iron is more available to plants as soil pH decreases. |
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| Your irrigation water influences what happens to your soil pH as the crop progresses. Although common sense would seem to indicate that your water pH affects your soil pH, it is actually your alkalinity that we are most interested in. Alkalinity is a measure of the buffering capacity of your water, and it tells us what effect your water will have on your soil pH over time. Alkalinity values of greater than 150 will place upward pressure on soil pH. |
| Sometimes we can manage this with acid forming fertilizers such as Excel 21-5-20. Depending on the desired pH range for the crop being grown, alkalinities over 180 may require acid injection. Griffin offers free alkalinity tests that allow us to match your fertilizer program to your soil and crops, and make acid injection recommendations when needed. If your water test indicates this we provide recommended rates as well as procedures for safe handling of these materials. |
| Low alkalinity water has a low resistance to pH change. In other words, if your water has alkalinity values below 80 and you continually use acid forming fertilizers you may drive your soil pH too low. Soil pH values that are too low can be remedied by applications of a flowable limestone product such as Limestone-F, or by using potassium bicarbonate. Griffin can supply you with both of these products. A detailed bulletin on using these products to quickly and safely raise soil pH titled, "Raising Soil pH During Crop Production" is available upon request from Griffin's technical department. |
| Optimizing your soil pH requires that you measure it at regular intervals during the crop cycle. The Scott's testing lab can quickly and accurately report your media pH, as well as other important indicators. Many growers keep tabs on pH and soluble salts by using the pour thru or 2:1 testing techniques with reasonably priced meters available from Griffin. Our technical department can help you master these techniques and put these numbers to good use in your production program. |
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