When you apply fertilizers through the irrigation water, it is essential that you know some important facts about fertilizers solubility.
What Is Fertilizer Solubility?
Solubility of a fertilizer is the maximal amount of the fertilizer, that can be completely dissolved in a given amount of distilled water at a given temperature.
Manufacturers may provide you with solubility data of their products, upon request. Here is an example of solubility data for Potassium Nitrate (expressed as g/liter):
Temperature (CÚ) 5 10 20 25 30 40 Solubility 133 170 209 316 370 458
Different manufacturers may provide slightly different solubility data for the same fertilizer. This is because they use different additives in their products. There are also some products that may contain insoluble residues.
Dissolving Fertilizers In Water
When you dissolve a fertilizer, you should not exceeds its solubility. Otherwise, a precipitate may form, and might clog the irrigation system. Moreover, the nutrients you intended to provide through the solution may not be fully available.
For example, according to the data in the table above, the solubility of Potassium Nitrate in 20oC is 209 g/L, and the fertilizer contains 38% Potassium. If you attempt to dissolve 300 g/L in the stock tank, you will not get 114 g/L of Potassium (38% of 300g), but only 80g. The remaining 34g have precipitated and will not be available.
Mixing Two Or More Fertilizers Together
When dissolving together two or more fertilizers that contain a common element (for example Potassium Nitrate together with Potassium Sulphate) the solubility of the fertilizers is decreased. In this case, we cannot refer to the solubility data alone. The same happens when the water used for dissolution is highly rich with minerals, e.g. Calcium, Magnesium or Sulphate.
In such cases, additional chemical reactions come into play, and calculations become more complex. Usually, these are not calculated in the field and instead, trial-and-error practices are common.
Some fertilizers should not be mixed together in one stock tank because an insoluble salt may form very quickly. An example for such incompatibility is mixing fertilizers that contain Calcium with those that contain Phosphate or Sulphate.
Preforming The Jar Test
We've established that when mixing fertilizers, we should be familiar with the solubility data of the fertilizers we use as well as with chemical reactions that may take place. In order to avoid unwanted precipitates, a common recommendation is to perform a "jar test". In this test, the fertilizers are initially mixed in a jar containing the same water used for irrigation. The fertilizers should be added exactly in the same concentration as intended to be used in the stock tanks. If a precipitate forms or if the solution has a "milky" appearance, the test should be repeated with lower concentrations of the fertilizers.
All these facts are automatically incorporated into the simple fertilization 'recipes' produced by Smart! - in a click of a button.
Guy Sela is an agronomist and water specialist. In 2005 Guy developed a unique software for fertilizer management that help growers to reach higher and better yields, save time and frustration and increase their profits.
Visit my website at:
http://www.smart-fertilizer.com
Source: www.isnare.com
