Plant growth system

1. A plant growth system comprising:

one or more plant growth substrates ( 1 , 2 );

wherein each substrate ( 1 , 2 ) comprises a man made vitrous fibre {MMVF} slab ( 1 ) and a MMVF block ( 2 );

wherein each MMVF slab ( 1 ) comprises a first upper layer of MMVF in interfacial contact with a second lower layer of MMVF, the first upper layer having a greater density than the second lower layer;

one or more detectors ( 7 ) arranged to monitor nutrient levels of at least one of the plant growth substrates ( 1 , 2 );

at least one irrigation device ( 6 ) arranged to supply water to the plant growth substrates ( 1 , 2 ); and

control means ( 9 ) connected to said detectors ( 7 ) and said at least one irrigation device ( 6 ),

wherein the supply of water by the at least one irrigation device ( 6 ) is controlled by the control means ( 9 ) in accordance with an irrigation strategy such that the amount of water provided to the plant growth substrates is metered in dependence on the monitored nutrient levels within the plant growth substrates to control the water content level therein while maintaining nutrient content levels of the plant growth substrate within a desired range;

wherein the one or more detectors ( 7 ) are arranged to determine the nutrient level from an electrical conductivity level of fluid in at least one plant growth substrate ( 1 , 2 );

wherein the electrical conductivity level is maintained within a predetermined range.

2. A plant growth system according to claim 1 , wherein the one or more plant growth substrates ( 1 , 2 ) are man made vitrous fibres (MMVF) plant growth substrates.

3. A plant growth system according to claim 1 , wherein the one or more detectors ( 7 ) are further arranged to monitor water content levels of at least one of the plant growth substrates ( 1 , 2 ), and the supply of water by the at least one irrigation device ( 6 ) is controlled by the control means ( 9 ) in dependence on the monitored water content levels.

4. A plant growth system according to claim 1 , wherein the at least one irrigation device ( 6 ) is further arranged to provide nutrients to the plant growth substrates ( 1 , 2 ).

5. A plant growth system according to claim 4 , wherein the supply of nutrients by the at least one irrigation device ( 6 ) is controlled by the control means ( 9 ) in dependence on the monitored nutrient levels.

6. A plant growth system according to claim 1 , wherein the one or more detectors ( 7 ) are further arranged to monitor the distribution of at least one of water or nutrients within at least one of the plant growth substrates ( 1 ).

7. A plant growth system according to claim 1 , wherein the one or more detectors ( 7 ) are further arranged to monitor the temperature of at least one of the plant growth substrates ( 1 , 2 ), and the supply of water by the at least one irrigation device ( 6 ) is further controlled by the control means ( 9 ) in dependence on the monitored temperature.

8. A plant growth system according to claim 1 , wherein the slab has a volume in the range of 3 to 20 litres.

9. A plant growth system according to claim 8 , wherein each plant growth substrate ( 1 ) further comprises a single MMVF plug ( 4 ) disposed within the MMVF block.

10. A plant growth system according to claim 1 , wherein the first layer of MMVF has a density in the range 40 to 90 kg/m 3 and the second layer of MMVF has a density in the range 35 to 85 kg 3 .

11. A plant growth system according to claim 1 , wherein each MMVF slab ( 1 ) comprises a binding system comprising an organic binder selected from formaldehyde-free binders.

12. A plant growth system according to claim 1 , wherein two or more detectors ( 7 ) are arranged to extend through a side wall of the slab ( 1 ) such that, in use, the nutrient levels are monitored at different heights of the slab ( 1 ).

13. A method for managing irrigation of a plant growth system comprising one or more man made vitrous fibres (MMVF) plant growth substrates ( 1 , 2 ), the method comprising:

monitoring nutrient levels of at least one of the plant growth substrates;

wherein monitoring nutrient levels comprises determining the nutrient content from an electrical conductivity of fluid in at least one plant growth substrate ( 1 , 2 ) using one or more detectors ( 7 ) arranged in the at least one of the plant growth substrates;

wherein each substrate ( 1 , 2 ) comprises a MMVF slab ( 1 ) and a MMVF block ( 2 );

wherein each MMVF slab ( 1 ) comprises a first upper layer of MMVF in interfacial contact with a second lower layer of MMVF, the first upper layer having a greater density than the second lower layer;

providing at least one irrigation device ( 6 ) arranged to supply water to the plant growth substrates ( 1 , 2 ); and

providing a control means ( 9 ) connected to said detectors ( 7 ) and said at least one irrigation device ( 6 ),

supplying water to the plant growth substrates ( 1 , 2 ) by the at least one irrigation device ( 6 ), wherein the supply of water is controlled by the control means ( 9 ) in accordance with an irrigation strategy such that the amount of water provided to the plant growth substrates is metered in dependence on the monitored nutrient levels within the plant growth substrates to control the water content level therein while maintaining nutrient content levels of the plant growth substrate within a desired range; and

maintaining the electrical conductivity level within a predetermined range.