In the United States, when you think of places that experience drought conditions, often California and Texas come to mind. However, in the last 8 months many central and western states have experienced abnormally dry seasons causing drought conditions. You would not think that parts of Minnesota and Wisconsin at this time of year would have moderate drought conditions. In the eastern United States even New York, Pennsylvania, Tennessee, Georgia and Alabama have seen abnormally dry conditions and moderate drought. Currently, parts of Arizona, California, Colorado, Kansas, Nevada, Oklahoma, Oregon, Texas and Utah are experiencing extreme or exceptional long term drought conditions lasting more than 6 months.
For growers, drought conditions can have a significant impact on water availability and crop production costs. Making the most efficient use of irrigation water is important to conserve this valuable resource. If we look at various types of growing media in terms of water conservation, some are better than others for optimizing water use. For example, bark based mixes typically are the least efficient for water use and conservation. Bark mixes have the lowest water-holding capacity and highest drainage, therefore require frequent irrigation.
Sphagnum peat moss has the highest water holding capacity of all of the organic materials used as a bulking material for growing media. However, when peat is amended with aggregates such as perlite and/or pumice to increase air porosity, water holding capacity is decreased. In comparison, coconut coir can have a high water holding capacity similar to Sphagnum peat moss, however it must be carefully processed so that the fibers continue to hold water and structure is retained.
Coir is used in agriculture and horticulture mostly as the processed pith of the coconut husk. It is often compressed into slabs for greenhouse vegetable production, but is rarely used as the sole component for horticulture growing media. For horticulture growing media, coir must be washed and leached to reduce the EC (electrical conductivity) from the naturally occurring salts found in the coconut pith. Then it is generally blended with Sphagnum peat moss and other components to form growing media.
Coconut husk is unique in that it can also be cut into various size ’chunks’, which can be used as aggregates for growing media. The benefit is that these coir chunks provide structure and porosity to increase air capacity and drainage of growing media, much like bark and perlite. However, bark and perlite reduce water retention of growing media, whereas coir chunks add porosity and increase water retention. Coir chunks accept water readily and act as small water reservoirs. This is the basis for PRO-MIX® HP-CC MYCORRHIZAE™ and another PRO-MIX® product containing 40% coir chunks that will be launched later this Spring. Both products contain coir chunks that are cut to specific size. The addition of chunk coir improves air porosity of growing medium while maintaining a high water holding capacity.