Plant growth substrates
A man-made vitreous fibre (MMVF) plant growth substrate is provided. The substrate has properties including a volume of 3 to 20 litres, two layers of differing density, and the use of an organic binder selected from formaldehyde free binders. This is found to provide a substrate which allows excellent control of the water and/or nutrient contents within the substrate when used for plant growth.
1. A man-made vitreous fibre (MMVF) plant growth substrate comprising a coherent slab having the following properties:
(a) a total volume in the range 3 to 15 litres,
(b) a first slab layer of MMVF having a density in the range 40 to 90 kg/m 3 ,
(c) in interfacial contact with the first slab layer, a second slab layer of MMVF having a density in the range 35 to 85 kg/m 3 that is lower than the density of MMVF of first slab layer; and
(d) the MMVF of both slab layers is bonded by an organic binder selected from formaldehyde-free binders;
wherein the substrate further comprises a liquid impermeable covering surrounding the first and second slab layers, the covering having a first opening disposed on a first face of the slab adjacent to the first slab layer and is provided for engagement of the first slab layer with a plant-containing man made vitreous fibre block;
whereby the liquid impermeable covering provides closer control of plant growth conditions.
2. The substrate according to claim 1 , wherein, in use, the first slab layer of MMVF is disposed above the second slab layer of MMVF.
3. The substrate according to claim 1 , wherein the binder is comprised in a hydrophilic binding system.
4. The substrate according to claim 3 , wherein the binder system comprises the binder and a wetting agent.
5. The substrate according to claim 4 , wherein the binder system comprises an ionic surfactant.
6. The substrate according to claim 5 , wherein the surfactant is an anionic surfactant.
7. The substrate according to claim 6 , wherein the anionic surfactant is a linear alkyl benzene sulphonate anionic surfactant.
8. The substrate according to claim 1 , wherein the binder is a reaction product of a polycarboxylic acid component and a polyol and/or an amine component.
9. The substrate according to claim 8 , wherein the binder is a reaction product of a polycarboxylic acid or anhydride thereof, an amine, preferably an alkanolamine, and a sugar.
10. The substrate according to claim 9 , wherein the sugar is a reducing sugar.
11. The substrate according to claim 8 , wherein the binder is in admixture with a sugar component and/or a phenol.
12. The substrate according to claim 1 , wherein at least one of the slab layers extends across an entire plane of the slab.
13. The substrate according to claim 12 , wherein both of the slab layers extend across an entire plane of the slab.
14. The substrate according to claim 13 , wherein the slab layers are of equal dimensions in the plane.
15. The substrate according to claim 1 , wherein the density of the first slab layer is in the range 50 kg/m 3 to 80 kg/m 3 .
16. The substrate according to claim 1 , wherein the density of the second slab layer is in the range 45 kg/m 3 to 75 kg/m 3 .
17. The substrate according to claim 1 , wherein the thickness of the first slab layer is less than the thickness of the second slab layer.
18. The substrate according to claim 1 , wherein the substrate further comprises a second opening provided on a second face of the slab adjacent to the second slab layer.
19. A plant growth system, comprising:
the substrate of claim 1 , and
a single plant-containing man made vitreous fibre block in contact with the first slab layer.
20. The substrate according to claim 1 , wherein the predominant fiber orientation of the first and second slab layers is horizontal.
21. The substrate according to claim 1 , wherein a base is added to the organic binder.