Thursday, April 16, 2009

Nursery, Greenhouse, Turf, and Landscape - Soluble Salts

The following is information problems related to high soluble salts in landscapes, greenhouses, nurseries, and turf.

Each year we see plant damage in turf, landscapes, greenhouses, and nurseries due to high levels of soluble salts in soils or media. High soluble salts can come from a number of sources: deicing materials used in the winter; excessive fertilizer, manure, or compost use; “dumping” of fertilizer salts from certain slow release fertilizers; and irrigation water that is high in salts. Excessive soluble salts can result in reduced growth, loss of vigor, root death, yellowing of leaves, wilting, marginal leaf burn, or plant death. This occurs because soils or media with high salt levels make it more difficult for plants to take up water, or if very high will cause loss of water from roots. Foliage exposed to high salt levels will show symptoms similar to leaf scorch. There is also a potential for certain elements to become toxic in high salt conditions: examples would be sodium or ammonium.

A common problem is over application of fertilizers. This can occur with miscalculation of fertilizer rates or dilutions, poorly calibrated or malfunctioning fertilizer applicators or injectors, or excessive overlapping during application. All soluble fertilizer nutrients (nitrate, ammonium, potassium, calcium, magnesium, chloride, sodium, or sulfate ions), contribute to the soluble salt content of the soil or media. However, some soluble fertilizers have greater chance for salt injury than others. Refer to the salt index of a fertilizer to evaluate the potential to cause salt injury. Certain manures and composts can also contain high salt levels. In greenhouses or nurseries, salt levels often build up in media due to inadequate leaching or poor pot drainage. Dumping of salts from coated slow release fertilizers can also occur in greenhouse and nursery production, especially if fertilizer coatings were damaged in handling or by exposure to excess heat.

If you suspect high salts in soil or media, a soluble salt test should be done (the UD soil testing lab and other soils labs can do this test). Soluble salt content is determined with an electrical conductivity meter using a specified dilution of soil or media. An electrical conductivity meter is a useful instrument for growers, turf professionals and landscapers to have on hand for troubleshooting salt related problems.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

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