A plant growth system is provided, which includes: one or more plant growth substrates comprising an MMVF slab and a single MMVF block; one or more detectors arranged to monitor at least one of the water and nutrient levels of at least one of the plant growth substrates; at least one irrigation device arranged to supply water and nutrients to the plant growth substrates; and control mechanism connected to said detectors and said at least one irrigation device. The supply of water and nutrients by the at least one irrigation device is controlled by the control mechanism in dependence on the monitored water and/or nutrient levels. In this manner, the water and nutrient levels of the substrates can be accurately controlled.