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Natural resaturation with coco coir

For many years, Van der Knaap has used a variety of coco products. For example, Knaap Profit Extra, the coarse coco chunks that create structure and stability in potting soil. Or Coco Crunch, short coco fibres that ensure a good water distribution ratio, and sufficient drainage if excess water is given. And Knaap Basic, the versatile and widely applicable coir from Van der Knaap with a high air-holding capacity.

Properties of coco

All coco products share an easy water absorption capacity. For this reason, coco coir is contained in potting soil mixtures used to grow plants in drier conditions. Coco coir can offer the solution in circumstances where dry patches tend to occur easily.

Bedding plants

One of the cultivations where Knaap Basic (coco coir) offers added value is bedding plants. The time when plants are potted up at the end of the year to over winter and spend a lengthy period ‘as dry as possible’, can result in a lack of uniformity. Once uniformity has been lost, it is a challenge to get the plants consistent again. In the dark winter months and early spring when less water is given, pots can dry out very rapidly. Pots that stay relatively moister can reabsorb water with no trouble and retain the required moisture level more easily. Drier pots have more difficulty; they absorb insufficient moisture whereby the differences between wet and dry continue to increase. In these, but also many similar situations, adding coco can be the solution.


To illustrate this, we sent two mixtures to an external laboratory to determine the Water Absorption Capacity (WAC). WAC-analysis is a standardised analysis method used to determine the degree of resaturation. The potting soil is dried, then spread over a thin layer of water. Subsequently, the time it takes the potting soil to absorb the water is measured.

WAC-analysis was performed on two potting soil mixes for bedding plants. Blend 1 was a ‘traditional’ bedding plant mixture. Blend 2 was the same mixture, but with a small proportion of peat replaced by Knaap Basic. Analysis reveals that the total water absorption remains the same (see graph and table): 74% with blend 1 and 73% with blend 2.

However, the 50% moment, that indicates how many minutes it takes to absorb 50% of the moisture, shows a huge differen- ce. Blend 1 recorded 39 minutes, while blend 2 recorded just seven minutes. After 15 minutes, blend 2 had reached a moisture content of 64% - which represents 90% of the total moisture content. With blend 1, the traditional bedding plant mix, this took 60 to 90 minutes.

A mixture that contains a proportion of coco, simply absorbs water faster. Dry pots will absorb water, and disparities in growth between plants in dry and wet pots will be reduced or even prevented entirely. A brief irrigation session is more than enough to hydrate the pots.

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