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Peat-Chunk Coir Growing Media: Benefits for Extraordinary Drought

Thursday, September 15, 2022 | Ed Bloodnick

In the United States, when you think of places that experience drought conditions, often California and Texas come to mind. However, many other states have experienced abnormally dry seasons causing drought conditions in the past. You would not think that parts of Minnesota and Wisconsin 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. 

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^® HPCC MYCORRHIZAE™. This product contains 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.

Coir chunk mixes comparison for drought

60/40 - peat/chunk coir

Plant Variety: HEUCHERA "KIRA OAK"

Started: Transplanted from plug into 1 gallon container

Evaluation: After 183 days

Plant Variety: Hosta "Big Daddy"

Started: Hosta root planted into 1 gallon container

Evaluation: After 17 weeks

PRO-MIX^® HPCC MYCORRHIZAE™

Plant Variety: Begonia "White"

Started: Begonia plug transplanted into 5-inch pot

Evaluation: 7 weeks after transplanting

In our comparative plant growth trials of peat-chunk coir growing media and other standard growing media, peat-chunk coir growing media significantly reduced the need for water and irrigation frequency. Why is this important?

1. With irrigating crops, a certain percentage of water runs over and out the bottom of the pot. When irrigation frequency is reduced, fewer water applications equals less water ‘wasted’. On average, there can be up to 25% reduction of water requirements for chunk coir growing medium compared to standard peat-based growing media. In regions where water is limited, peat-chunk coir growing media can conserve water.
2. Cost of Water. Whether water is purchased or you have your own well, there are costs associated with water usage for price/gallons or electric cost for pump. Peat/chunk coir growing media can reduce water usage resulting in a 25% cost savings. Also, with less irrigation applications, there are labor savings, since workers spend less time watering crops.
3. Plant growth can be impacted by temperature of irrigation water. Unless the water in your greenhouse is heated, tap water can be cold. Every time you irrigate crops with cold water, there is a shock to the root zone and the growing medium temperature is reduced. If you water up to 25% less, plants roots system experience less crop stress resulting in improved plant growth.

In regions of drought and water restrictions, peat-coir chunk growing media can reduce irrigation frequency and overall water requirements. This type of growing media makes more efficient use of irrigation water for cost savings and reduction of labor costs. For information about how you can save water with PRO-MIX^®, contact your Premier Tech Sales Representative.

U.S. Drought Monitor Map example

For more information about drought conditions, refer to the U.S. Drought Monitor website droughtmonitor.unl.edu. The US Drought Monitor is a weekly map of drought conditions that is produced jointly by the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture, and the National Drought Mitigation Center (NDMC) at the University of Nebraska-Lincoln.