Using coir as a growing substrate

Provided by Shan Halamba
Edited by David Kuack

Coir is a natural, and renewable resource produced from mature coconut husks. Coir fiber is a coarse material obtained from the husk surrounding the coconut seed.
Coconut palms (Cocos nucifera) yield coconuts, which are harvested in 45-day cycles. The husks are separated from the nuts, which are consumed as food. The husks are used to produce growing substrates. The husk fiber is spun into a wide range of textured yarns. These yarns are used to produce a variety of products including colorful woven floor coverings.
Sri Lankan coir
Sri Lanka is the largest exporter of coir in the world. The coir industry began in Sri Lanka in the 1860s. Over the years, piles of coir gradually grew around coir mills and the country faced a major disposal problem. In the late 1970s, coir fiber products started to be exported to many different countries. European customers realized that the coir from Sri Lanka had desirable horticultural properties.

RIOCOCO coir substrates
RIOCOCO coir substrate products originate from Kurunegala in the heart of Sri Lanka’s coconut triangle. Here the coconut palms flourish in the region’s rich soil and humid tropical climate.
RIOCOCO coir was introduced in 2004 after many years of extensive testing, research and development combined with customer feedback. Carefully selected raw materials are blended together to produce high quality coir substrates in different formats. RIOCOCO owns eight production facilities in Sri Lanka. These operations have the capacity to produce 4 million greenhouse grow bags per year along with other growing medium products.
RIOCOCO coir characteristics
RIOCOCO coir is lightweight and can be compressed into a variety of shapes. It decomposes slowly due to its high lignin content. It is uniform and consistent because of the production process that uses various sieving systems and mixes different particle grades.
RIOCOCO coir is widely available and doesn’t create any environmental problems during the production process like other inorganic growing media. RIOCOCO is the first North American-based company to obtain the OMRI listing for coconut fiber.
RIOCOCO coir has excellent porosity and water holding capacity, which can be changed according to crop requirements by blending different grades of coir. It has ideal chemical characteristics for plant production. It can be reused for several crop cycles and can be easily disposed of without any environmental concerns.
RIOCOCO is conducting research to develop the next generation of products that will be suitable for different and new growing techniques. Each product is tested under different greenhouse conditions in temperate countries including the United States, Mexico and Japan.
Hydroponic production in coir
Currently, tomatoes, cucumbers, bell and chili peppers, egg plants and strawberries are grown hydroponically in custom blended RIOCOCO coir grow bags. These production systems include low-tech and high-tech greenhouses and nursery container systems.
RIOCOCO products consist of different blends based on the requirements of specific crops and the duration of the crop cycle.
Every crop has a specific air fill porosity and water-holding capacity. When the water-holding capacity of a growing medium is too high, root diseases such as Pythium and Phytophthora can occur. A growing medium with a water-holding capacity that is too low causes water stress and results in poor plant development.
Another important characteristic of a growing medium is stability. Growing media consisting of smaller particles are decomposed faster by micro-organisms. Many of the coir substrates on the market contain smaller particles that will decompose in the slab or pot after a couple of years in production.
Crops like bell peppers that have a long cropping period require a more stable substrate such as a blend of coconut husk and coir. RIOCOCO has developed a special mix for bell peppers that contains different particle sizes of husk chips and natural materials. This open mix has a higher water-holding capacity and air fill porosity.
Different mixes are also available for container-grown plants. A major consideration is the method of irrigation. For container plants produced with ebb-and-flood irrigation a more open substrate that holds enough water is needed.

Coir adjustments
RIOCOCO coir is washed and dried to remove excess sodium before it is blended and manufactured into slabs and blocks. These coir products are not pre-buffered with calcium which enables growers to make this adjustment depending on the crops’ requirements.
Buffering coir prior to use is necessary and can be done by applying additional calcium nitrate and less potassium nitrate to the nutrient solution when expanding the slabs and during the first two weeks of production. After this period standard nutrient formulations can be used.
The root activity in coir slabs is higher than in other organic and inorganic substrates resulting in a higher pH. This increase in pH can lead to a poor uptake of iron.
For growers who normally apply Fe-EDTA, a part or even all of the iron has to be applied as Fe-DTPA, Fe-EDDHA or Fe-EDDHMA. The reason is the high pH has an impact on the stability of the iron chelate. Once the iron chelate is unstable, plants cannot take up the iron. Fe–EDTA is stable until a growing medium of pH 6.7 while Fe–DTPA, Fe-EDDHA and Fe-EDDHMA are stable to a growing medium pH of 10
The electrical conductivity (EC) or conductivity factor (CF) of RIOCOCCO coir is comparable to other substrates.
Watering coir
There are no differences in fertilization for plants grown in RIOCOCO coir products compared to other growing media apart from the nutrient adjustments previously mentioned. Since coir holds water much better than other inorganic substrates, less water needs to be applied and it is readily available to the plants.
In general, during the summer drain percentages of 20 to 30 percent are obtained. During the winter less water has to be applied as coir can be easily over watered. A good method of controlling irrigation is to use a weight scale and work with a dry down of 10 percent for the coir slabs. In most cases a drain percentage of 10 to 20 percent is obtained.
RIOCOCO coir products
RIOCOCO coir products include slabs, trays, bags and containers. The slabs can be produced at any length, width and height to match any production system and crop. Special orders are possible such as layered slabs in which layers of different grades of coir are placed on top of each other. RIOCOCO can also make special blends for crops with different water-holding capacities and for long term crops.
For long term crops an important factor is the stability of the plastic wrapping around the slabs. Wrapping that is not UV-stable can deteriorate causing the slabs to fall apart and allowing weeds to grow in the coir. Upon request RIOCOCO slabs can be wrapped in UV-resistant plastic that is guaranteed to last for at least a year.

Shan Halamba is chief executive officer, Ceyhinz Link International Inc., Irving, Texas; (214) 492-0803; http://www.riococo.com/
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

Growing media considerations
A growing medium should provide support for the plant root system. The medium should also allow the roots to penetrate easily in search of water and nutrients. This means a medium should be able to provide ample pore space for oxygen and to hold water and nutrients.
The following are basic considerations when choosing a growing medium:
* Availability
* Weight
* Uniformity and consistency
* Optimal physical properties, including porosity and water-holding capacity
* Optimal chemical properties, including mineral ion concentration and pH
* Low decomposition
* Reusable and ease of disposal
* Cost
* Organic certification

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