Managing Saline Soils
Crop plants use water to transport nutrients throughout the plant as well as cool the plant through evaporation. Plants uptake water through the osmotic differential between the soil and the roots. Water movement in soil is mainly due to osmotic potential. The solute concentration in the root is
greater than that in the soil, so the water moves to the greater concentration in the root. Irrigating soils with water that contains Na+ or Cl+ causes a buildup of salts in the soil. Over time, this can cause the solute concentration to become greater in the soil than the root. Clean surface water from river or lake
sources greatly slows the buildup of salts in the soil. In years with drought, as we have experienced
for the last several years, we rely more heavily on well water, which has a tendency to have higher amounts of dissolved salts. This accelerates the buildup of salts in soil we are trying to farm.
To manage this salt build up, there is a need for a leaching fraction of water to help flush the salts past the root zone. Depending on your crop, soil type, severity of salinity and several other factors, you can calculate what the leaching fraction should be. The best way to manage your leaching fraction is to have water and soil samples available to understand how severe the salt buildup is in your soils and how much water will be required to flush. The cleaner your water, the more effective your leaching fraction will be at flushing salts. The Western Fertilizer Handbook published by the Western Plant Health Association offers several other management practices to help with salts:
- Selection of crops or crop varieties that have tolerance to salt or sodium.
- Use of special planting procedures that minimize salt accumulation in the seed or root zone.
- Use of site preparation and tillage methods that provide a low salt environment.
- Use of irrigation water in maintaining a high water content to dilute the salts or to leach the salts from the root zone.
- Use of physical amendments for improving soil structure.
- Deep tillage to break up hardpan or other impervious layers, thereby providing internal drainage.
- Use of chemical amendments.
- Establishment and maintenance of adequate surface and internal drainage.
As we move into the growing season, salts should be an important part of everyone’s management plan. Helena has many tools to help manage salts in soil as well as water. Please consult with one of our PCA’s or agronomists for more information.
- Don Paradise, Product Manager, Western Division