High sodium irrigation water and clay soil

Asked June 1, 2017, 12:33 PM EDT

I have a new well with sodium level at 75. I tried to calculate the SAR, but I don't know if I did it correctly. It came out between 3 and 4. Sodium is 75 mg/L. Calcium is 34.3 mg/L. Magnesium is 2.64 mg/L. pH 8. TDS 290.Iron 3.040. I used the water last year to irrigate, but it dried up the leaves of the trees and bushes that it touched. The grass survived. I have tried to figure out how to use the water for irrigation. I was considering using gypsum in a mixer system to apply the water to my clay soil to help prevent worsening sodic soil. I have only an acre, but would love to be able to provide grass for my llamas and irrigate my garden. 1. Is it possible to use gypsum to help negate the negative impact of the high sodium on my soil? 2. How do I know how much gypsum to use to mix with the irrigation water? Thanks. I live in Eugene, Oregon

Oregon irrigation and water management pastures and forages horticulture

1 Response

Good morning, and thank you for your question! Before we explore water treatment options, would it be possible for you to provide me with a copy of the lab analysis for your water? I want to make sure I am interpreting all of the units correctly. Based upon the information you've provided already, your water doesn't appear to be too far out of line. A sodium level of 75 mg/L is equivalent to 3.26 mmol/L, and 3 mmol/L is the division between "no" and "slight" degree of restriction for use on sensitive crops. If possible, please send a copy of your results to jeff.choate@oregonstate.edu.