Proper processing of coir to lower its natural high salts level should eliminate the need to buffer it with calcium nitrate.
Coir has become a major component of both greenhouse vegetable and container crop production. It can be used by itself, for instance in grow bags, slabs and propagation cubes, or it can be used in growing mixes with other components like sphagnum peat, perlite and bark.
Coconuts, which are produced by coconut palms (Cocos nucifera), consist of husks that surround the nuts. The nuts are consumed as food and the husks are used to produce various types of coir growing substrates, including chips, chunks and peat. Coir peat is a by-product of the husk fibers that are used to fill cushions and car seats.
Naturally high in salts
Dr. Hugh Poole, international agricultural consultant, said coconut coir is initially high in sodium, potassium and chloride salts.
“Where the coconut coir originates from can have an impact on the salt levels,” Poole said. “Coconut palms produced inland away from the ocean may not accumulate as much sodium, potassium and chloride, but growers should assume that all coconuts will have high salt levels.
“These salts are relatively soluble and are not totally bound by the coir so they are easily leached. Most coir producers use rain water for most of the year to remove the salts. If the EC (electrical conductivity) level is below 1.0 milliSiemens per centimeter (mS/cm), growers should not have to leach the coir. In most cases, the coir producers have already leached the coir for the growers. It should be ready to use. If the salts level is high, then the coir producer has not done its job. A producer should be able to provide growers with the coir’s EC value, its pH value and other information, including percent moisture, as well.”
Poole advises growers using coir to test for soluble salts before it is combined with other mix components and before any plants are placed in the coir.
“If the level of salts is low, then a grower doesn’t need to worry about sodium, potassium and chloride,” he said. “Many growers say the soluble salts level should be less than 1.0 mS/cm. Others say the salts level should be less than 0.5 mS/cm. It really comes down to how the coir is going to be used. If Ellepots are going to be filled with coco peat for young seedling production, then the soluble salts level should be around 0.5 mS/cm. If the coco peat is being blended with sphagnum peat, perlite or some other growing mix components and plants are being transplanted into containers, the coir soluble salts level can be higher. I have seen EC values as high 3-6 mS/cm. In these instances, unless the coir is being diluted with a lot of other mix components, growers would certainly want to leach the coir before it is used.”