Vermiculite Applications

Horticulture

 

 

Home Page

 
 
Vermiculite has established itself as a firm favourite amongst many discerning growers who appreciate the improvements it gives to their compost formulation. They read about its features - sterile, extremely lightweight, high exchange capacity, but can actually appreciate those benefits in the quality of the plants they produce. It improves seed germination, stimulates vigorous growth, discourages damping off, reduces pricking out losses. All of these lead to increased yield and quality and therefore more profit.

More Air Filled Pore Space (A.F.P.)
Every grower knows that plants fail to grow in a solid block of concrete so it's surprising some try to make their compost like one. The air / water relationship provides a measure of the room available within a compost for the essentials of growth - air, water, nutrients and roots. The graph shows changes in A.F.P. with different mixtures of Vermiculite and peat. A.D.A.S. tests indicate that an A.F.P. figure between 10 - 15% is suitable for growing media.

 

More Water Carrying Capacity

It is essential that composts have the ability to hold water ready for plant use. The chart gives comparisons between water carrying capacities of various materials commonly used in composts.

More Cation Exchange Capacity

The cation exchange capacity (CEC) of a growing medium, is a measure of the exchangeable cations it can absorb per unit quantity. For lightweight materials it is better expressed in terms of milligram equivalents per litre, although conventionally for soils it is stated per 100 grms. The major exchangeable cations present in growing media are Ca++, Mg++, K+, NH4+, NA+, and H+ and a materials ability to regulate the supply of these nutrients to plants is indicated by its CEC. A particularly valuable feature of a material with a high CEC, is the way it controls the rate of release of Ammonium and Potassium ions from added fertilisers.

 
 
More nutrients

Originally thought to be inert, more refined analytical techniques now show several useful elements in Vermiculite potentially available for plant growth. These involve replacing water in the usual solubility tests with an extractant more closely modelling conditions found in compost. Giving values for Vermiculite of around 500mg/l Potassium and 300mg/l Magnesium together with small amounts of Calcium and Sulphur. Manganese and Iron are also present.

 
 
 

Grades

Grade

Size

Typical Density kg/m3

Uses

Fine

2mm down

100

Seed sowing and moist growing media.

Medium

4mm down

78

General purpose growing media.

Large

8mm down

70

Extra winter drainage, bulb culture and storage.
 

Recommended Mixes

"Seed Sowing" and "Premier Potting" have been formulated to give optimum results. The "Economy Universal" is for those growers who require a reliable mixture but with the emphasis on economy.

Seed Sowing, Cutting and Module Compost 50% v/v Vermiculite, 50% sphagnum peat - then to each m3 add the following:- 1000g Simple Superphosphate Powder, 500g Sulphate of Ammonia Crystal, 350g Fritted Trace Element WM255, 1200g Magnesium Limestone Powder.
Premier Potting Compost 25% v/v Vermiculite, 75% sphagnum peat - then to each m3 add the following:- 2750g Simple Superphosphate Powder, 800g Nitrate of Potash Crystal, 1000g Sulphate of Ammonia Crystal, 350g Fritted Trace Element WM255, 4500g Magnesium Limestone Powder.
Economy Universal 10% v/v Vermiculite, 90% sphagnum peat - then to each m3 add the following:- 1500g Simple Superphosphate Powder, 750g Nitrate of Potash Crystal, 500g Sulphate of Ammonia Crystal, 350g Fritted Trace Element WM255, 3800g Magnesium Limestone Powder
 
   

Relevant products:

Dupré DF

Dupré DL

Dupré DM