Soil Salinity and Plant Sensitivity to Salts
Some forms of compost and manures can be high in salts. Avoid these amendments in soils that are already high in salts (above 3 dS/m) or when growing plants that are sensitive to salts. Raspberry, strawberry, bean, carrot, onion, Kentucky bluegrass, maple, pine, viburnum and many other landscape plants are salt sensitive. In such cases, choose sphagnum peat or ground leaves instead of compost or manures.
Salt Content and pH of the Amendment
Always be aware of salts in soil amendments. High salt content and high pH are common problems in Colorado soils. Therefore, avoid amendments that are high in salts or that have a high pH. Amendments high in salts and/or pH include: wood ash, Colorado mountain peat and composted manures. An amendment with up to 10 dS/m total salts is acceptable if well mixed into low-salt soils (less than 1 dS/mm). Amendments with a salt content greater than 10 dS/m are questionable. Choose a low salt amendment for soils testing high in salts.
Sphagnum peat and compost made from purely plant sources are low in salts and are good choices for amending Colorado soils. Ask for an analysis of the organic amendments that you are considering, and choose your amendments wisely. If no analysis is available, test a small amount of the amendment before purchasing a large quantity.
For more information, please see fact sheet 7.235, Choosing a soil amendment.
