Mineral nutrition studies of coffee trees XXX: sand culture tecnique for growing coffee trees

A sand culture experiment was installed in order to find out the possibilities of growing coffee trees (Coffea arabica, L.) for a long period of time. The experimental tecnique is diagramatically shown in figure I in the text: 1 - timer; 2 - air admitting solenoid valve; 3 - air escaping solenoid valve; 4 - air compressor; 5 - barometric pressostatic column; 6 - air filter; 7 - reducing pressure valve; 8 - nutrient solution reservoir; 9 - leveler; 10 - refill inlet; 11 - air retention valve; 12 - pot filled with quartz sand. Judging by the leaf analyses (tables 2 and 3) the technique seens adequate for growing coffee trees in nutrient solutions. At the present moment 36 units are in operation.