The solution that a root zone of a plant is exposed to will have a corresponding Ph value. In chemistry, this Ph value corresponds to the amount of Hydrogen ions, [H+] present in the solution. A solution with a low concentration of hydrogen ions will have a high Ph. Solutions with a high concentration of hydrogen ions will have a low corresponding Ph. The equation used to describe this is relationship is a negative logarithm and relatively complicated. This should not be used unless extreme accuracy is needed in adjusting the Ph of a solution. The Ph value of your irrigation water is VERY important for the nutritional uptake process. The chart below displays visually why the Ph is so important. The Ph scale on the x-axis goes from 4 (Acidic) to 10 (Basic / Akaline).
The thickness of each fertilizer band is the relative magnitude for which that element can be absorbed through the root tissue of the plant. When looking at the nitrogen band the thickest region of this element is between the bounds of roughly 6 and 8. If nitrogen is available in solution and the Ph is within this optimal range of 6 – 8, then the nitrogen uptake should be optimal. The optimal Ph range for a plant depends on its nutrient requirements. Looking at any value for Ph below it intersects vertically each of the elemental bands. The cumulative thickness of all of these elements represents the total magnitude of nutrient uptake. The Ph needed for most plants is between 5.5 and 6.5 and can be adjusted temporarily to help recover from nutrient deficiency.
When designing an irrigation application it is critically important to know specific details about your available water resources. Below is a New York City water sample analysis received by one of my costumers. You can see that the Ph is 6.37 coming from the municipal water supply which is slightly higher than what is desired for most agricultural applications. Therefore, equipment will be needed to lower the Ph of the incoming water. There are some options to accomplishing this and it will be discussed in more detail in a later post.