Understanding Plant Nutrition

Water is the key driver for plant growth and nutrition. It is used to irrigate and fertilize the soil due to its solubility. However, with its great capacity for performance, it can also leave room for unintended outcomes. Alkaline irrigation water can lead to alkalinity, salinity, and toxicity.

We’ve written vastly about soil salinity in past articles: Gypsum Optimizes Soil Management, Salinity in Water Irrigation Systems, and Roots Reserve Analysis. Today we will be discussing alkalinity. Alkalinity is defined as the capacity of water to neutralize acids (given the presence of bicarbonates HCO3- and carbonates CO32- anions) otherwise known as the buffering capacity. Neutralization is the process in which anions pair with cations calcium (Ca2+), magnesium (Mg2+), potassium (K+), sodium (Na+), and others.

Carbonates and bicarbonates are salts present in water. The increase in concentration increases the pH.

Risks Associated with Alkaline Soils

An increase in water alkalinity results in an amplified ability for soil pH change and the formation of water deposits on the outer surface of a plant’s leaf. The effect on plants can seem unnoticeable at first. That is because alkaline soils decrease the nutrient uptake of certain nutrients (i.e. iron, zinc, manganese). It won’t be until later that stunted growth and nutrient deficiencies are seen.

Additionally, an alkaline water source can create clogs in irrigation water systems (i.e. injectors and drip lines). Making for costly repairs down the line.

Managing highly alkaline irrigation water

To neutralize alkaline irrigation water one must acidify the water source to reduce the bicarbonate cations.

These are some popular acids to manage alkalinity (in order of neutralizing power/relative hazard). It should be noted that these acids will increase the acidity of the soil along with the base concentration of the acid itself.

• Sulfuric Acid
• Nitric Acid
• Phosphoric acid

Test, Before You Invest: What to do before adding acids to your irrigation water systems.

When reviewing a water suitability report, several questions that affect crop production need to be answered:

• What level of PH do you have?
• What electrical conductivity do you have and why?
• What level of sodium absortion rate do you have?
• What level of alkalinity do you have?

If you have any questions feel free to contact us about our agricultural water testing.