PLANT GROWTH CONTROL SYSTEM

A system (10, 11) for controlling plant growth conditions in hydroponic growing systems, the system for controlling plant growth conditions comprising: at least one detector (7, 22, 1101) for measuring at least one property of a plant growth substrate or environmental condition; first (9,1103) and second (9, 12, 1107) data processing means; data storage means (1120); and the or each detector (7, 1101) being arranged to measure a property or properties of a plant growth substrate or environmental condition and to transmit a detector identifier and the measured property or properties over a communications link to the first data processing means; the first data processing means (9, 1103) being arranged to: hold in a memory predefined growth data including irrigation data, environmental data, plant data, harvest data, crop data and/or climate data defining a relationship between: plural values for one or more of temperature, pH level, water content, nutrient content, oxygen content of the substrate, air temperatu