Greenhouse - Salt Damage from Overfertilization

Overfertilization in greenhouses can occur if attention is not paid to fertilizer programs. Malfunctioning proportioners, improper rate settings, improperly made up stock solutions, fertilizer dump from slow release sources and other problems can cause excess salts and can damage plants. The following is an article on the subject.

A common problem often diagnosed this time of year with spring crops is excess soluble salts. Generally, this is a result of too much fertilizer in relation to the plants needs. Inadequate watering or leaching, or poor drainage can also result in high soluble salts.

Sometimes high soluble salts levels occur when root function is impaired by disease or physical damage. Always check the condition of the root system when trying to diagnosis a problem.
Seedlings, young transplants, and plants growing in media containing 20% or more field soil are less tolerant of excess soluble salts.

Injury to bedding plants from excess salts seems to be most common shortly after transplanting. Seedlings are much less tolerant of salinity than established, rapidly growing plants. Small or slow-growing seedlings (e.g., begonia, petunia), poor quality seedlings, and rooted cuttings of New Guinea impatiens are easily harmed by excess salts.

Some soilless mixes may contain enough “starter charge” to cause excess salts problems in the first few weeks after transplanting, particularly when a water-soluble fertilizer is also applied
If you suspect you have a problem with excess soluble salts, the container/soil should be leached twice with clear water.

Reprinted from the New England Greenhouse Update, April 2005 edition.