How to use Medium and Coarse Substrates

Instructions for use of medium and coarse peat substrates.

Medium and coarse peat is a very good growing medium for repotting of plants that need a lot of air around their roots during an extra long cultivation period. High quality of a substrate consists of 3 parts: only high quality raw material has to be used, the substrate mixing has to be exact and professional and last but not least: application of the substrate on site has to be wise. This article is about the last, very important phase: use of peat substrate in the nurseries and greenhouses for the repotting process. The reason why peat is so good for plants lies partly in the physical features of peat: Total pore space, available to water or air; Air filled porosity; Water availability; Water buffering capacity. It is important not to remove these features while using peat substrate.

Decompression of bales. This is the first part of application of peat substrate on site; the reason for doing it is that the peat is compressed in bales in order to save transport cost. Compression rate is different for small bales and big bales and varies from 2.5 to 1.9. Goal: It is very important to decompress the material properly in order to achieve maximum porosity of substrate that is vital for roots and also maximum yield from one bale which is important from the cost point of view. Threats: If the peat is not properly decompressed, the yield is smaller and porosity % may be harmfully low for the plant.

Decompression technologies vary. It is possible to decompress mechanically with paddles, by hand with shovels, enhance the process with water. It is important to avoid breaking the peat particles during the process. If the yield is smaller due to insufficient decompression, you will not be able to fill enough pots with substrate and substrate price per pot will be higher than expected. If oxygen deficiency occurs due to insufficient decompression, the plant may suffer slower growth due to lack of air for roots, accumulation of toxic compounds and excess water in the substrate.

Filling of pots with decompressed material is the next very important stage. It is important not to compress the substrate too much during filling of pots. Optimum compression is 12%, but according to research, sometimes even 60% compression has been registered. If you compress too much, all the efforts that were made during the decompression of bales will be annulled. If the substrate is too compressed in pots there will be oxygen deficiency and this limits or stops the metabolic activity in roots, it may cause the roots to die, it may even create a favorable environment for different diseases. If the substrate is too firm in the pot, the water uptake is slower and bigger; growth of the plants is inhibited and after a certain time might even stop. If the pot is filled correctly and the substrate is loose enough, the water uptake, nutrition and growth are normal and the plants are bigger and healthier and endure long vegetation period well.

How to fill correctly? You should start by weighing the filled pots and adjust the filling machine accordingly. Is it important to know the density of loose substrate, this can be determined according to the EN 12578 standard with a 20L cylinder. All our production has declared volume inside according to this standard. For example, if a 275L bale weighs 50 kg, you calculate the density: 50/0,275 = 182 kg/cbm. If you have 1L pots and you wish to achieve the recommended 12% compression, one pot filled with substrate should weigh 204 grams without tare weight.

It is important to adjust the compression % during potting because it is not possible to adjust it during growing. As a result of adjusting this compression rate, there will be more optimum substrate use, better growing results and several unexplained poor growing results will disappear.