Proper processing of coir to lower its natural high salts
level should eliminate the need to buffer it with calcium nitrate.
By David Kuack
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.
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.”
Coir
producers should be able to provide growers with the coir’s EC value, its pH value and other information, including percent moisture.
Photos courtesy of
Riococo
|
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.”
Poole said growers who ask their suppliers for a low EC
coir is similar to asking for a low EC peat moss or compost.
“If growers have to deal with a growing mix component
with an EC level that is always bouncing around, it is going to be very
challenging for those growers from crop to crop and from year to year,” he said.
To buffer or not
to buffer
Poole said some growers are asking suppliers to buffer their coir with calcium nitrate.
Poole said some growers are asking suppliers to buffer their coir with calcium nitrate.
“These growers are thinking that the cation exchange
sites are loaded with potassium and sodium ions and if the coir isn’t buffered
with calcium nitrate then their crops may suffer a calcium or magnesium
deficiency,” he said. “These types of deficiency problems are more commonly
encountered with hydroponic systems. If a substrate is being used, then this
usually isn’t a concern.
“Most of the coir’s exchange sites are tied up with
sodium and potassium. These ions are readily replaced by calcium. If calcium is
applied, much of that calcium is going to be tied up in the exchange capacity
taking out sodium and potassium. Therefore calcium is not in the substrate
solution for utilization by the plants. There is a lag before the cation
exchange capacity can be fully charged with calcium, potassium and magnesium. If
a grower isn’t cognizant of this lag and doesn’t address it, it can cause
deficiency problems. When 50 ppm calcium is incorporated in the fertilizer
solution, the leachate may only contain 10 ppm calcium. Not that the plants
utilized the other 40 ppm. Much of that 40 ppm was tied up at the exchange
sites and will be available later.”
Avoiding
deficiency problems
Poole said if the coir’s EC level is initially low and
growers apply a Cal-Mag fertilizer at the beginning of a crop, there shouldn’t
be deficiency problems. He said growers using reverse osmosis water, in which
there is no calcium or magnesium, should make adjustments in fertility
especially if they are producing a fast growing crop. Although no deficiency
problems might occur, Poole said growers should be diligent in monitoring
fertility levels.
“Once the cation exchange sites are charged with calcium
and magnesium, then there is free exchange and there shouldn’t be any problems,”
he said. “In the first two to four weeks, growers should probably start out
with higher calcium and magnesium levels if they’re growing with coir. They
should try to favor calcium and magnesium absorption at the exchange sites. This
is a precautionary step.”
If
the coir’s EC level is initially low and growers apply a Cal-Mag fertilizer at the beginning of a crop, there shouldn’t be deficiency problems. |
Poole said growers, who are using coir and are planning
to use a 20-10-20 fertilizer, need to be aware that this fertilizer does not
contain any calcium, magnesium or sulfur.
“The growers are going to have to add these nutrients,”
he said. “If growers are using coir they have to recognize that the exchange
sites need to be filled or charged with calcium and magnesium before there
starts to be a free exchange of nutrients back and forth.
“With coir where the exchange sites are filled with
sodium and potassium, the only way of removing these ions is by reducing them
with leaching with water or by overcompensating with calcium and magnesium.”
Poole said initially, the natural salts found in coir
must be leached with water. The remaining salts will be exchanged with calcium
and magnesium by a buffering treatment or with elevated levels in the fertility
program. He said buffering is not an option for organic growers.
“If coir is washed well and its EC is below 0.5 mS/cm or
lower, then the coir shouldn’t have to be buffered for most crops. If calcium
nitrate is used to buffer the coir, magnesium has to be provided as well.”
Poole recommends growers should review both their water analysis
and their fertilizer analysis to know what nutrients they are applying and to
confirm nutrient levels.
“Young plants and bare-root plants are more sensitive to
high salts than to short-term nutrient imbalances,” he said. Long-term crops
should be monitored using tissue analyses to optimize plant nutrition and crop
productivity.
For more: Hugh
Poole, FloraSynergy; (864) 359-7090; hapoole@Interact2Day.com.
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