Hydroponics Salt Build up

Hydroponic Salt and Mineral Accumulation

Salt buildup causes salt burn damage in hydroponic systems.

Small amounts of salt and minerals are naturally present in nutrient solutions.

A salt buildup will occur when growing media, which has been continuously soaked with nutrient solution containing dissolved salts, evaporates faster than the minerals are absorbed by the root system, leaving behind a small amount with each subsequent cycle.

The moisture is absorbed by the atmosphere , but the minerals , which includes salt particles and mineral deposits remain behind. This increases the Electrical Conductivity {EC} in the media and root system.A salt buildup in the roots zone will increase the osmotic pressure around the root system and hence hamper osmosis. Osmosis is the process utilized by the plant for the uptake of water. Salt will also cause damage via direct contact with the plant, seedlings in particular, as well as interfere with nutrient ratios.

Leaching excess salts from the system using plain water will sometimes have bad results and unwanted side effects especially when a crop is growing.

Salt buildup is fairly easy to recognize – a white crusting is an early sign. Salt buildup appears as whitish crusts, crystals and residue on the surface of growing media and conduits, and eventually the base of plant . Media with porous surfaces , such as rockwool are more prone to salt crusting, and visible detection is hampered by the porous surface.

Media such as expanded clay granules, with a smoother surface area will develop a visible whitish coating on their surfaces. Ebb-and-flow systems are more prone to this.

Plant growth is soon retarded. The plants darken and harden. In more severe cases, the base of the plant as well as the roots will have a burnt appearance as they die back. Early signs of the dying back is wilting during the warmer times of day and, greater susceptibility to disease in these areas.

A sudden, radical change in osmotic pressure , hence osmosis can trigger a surge in moisture intake by the plants. In fruiting plants this leads to splitting, in leafy plants it leads to soft, low quality leaves.

Media should be flushed with a solution specifically designed for this purpose. A nutrient solution about 1/4 its normal strength can also be used to flush excess salts. The flushing process should be done monthly in most systems. In shallow systems with high evaporation/ transpiration rates more frequent flushes may be needed. Flushing completely between plantings is recommended.

Monitoring EC

Regular monitoring of the nutrient solutions EC will help with early detection of salt accumulation. The Electrical Conductivity of the nutrient solution should not deviate substantially as it flows through the root system. If the EC is increasing as it flows through the root system and out the base of the growing container, It is quite probable that salt buildup will /has occurred.

EC is a measurement of how much electric current can pass through a water sample. Distilled water for instance has no EC – it does not contain any salts. Fresh water has a very low EC- it contains small amounts of salt. Nutrient solutions have a high EC they contain high amounts of salts and minerals.

The more salt the water contains the higher the EC. There are so many different ways of measuring how much salt is in a water sample. The most common measurement for salt is in concentration units such as parts per million (ppm grams of salt per million grams of water) or TDS [Total dissolved salts].

TDS and EC, while relative to one another, are two different things. TDS represents any non organic, dissolved substance in water. TDS includes minerals, salts, and metals dissolved in water. TDS Meters  measure the EC and translate it to an estimated TDS level.