Soilless closed cycle production of green bean (Phaseolus vulgaris L.) using subirrigation: effects on yield, fruit quality, substrate and nutrient solution parameters

A soilless closed system experiment was conducted at MAIB greenhouse during the 2008 spring using subirrigation (trough bench system) for growing green bean. The effects of two substrates (peat+perlite and peat+sand 1:3, v/v) and two nutrient solution (NS) concentrations (100% and 50% of the macro-elements concentration normally used for growing this crop in soilless conditions) on yield, pod quality (categories, mineral composition), water use efficiency, and nutrients concentration into substrate and NS of two cultivars (‘Saporro’ and ‘Venda’) were evaluated. Trough bench technique allowed the realization of a continuous closed system with a major stability of the chemical parameters of the NS. It proved to be more effective than open soilless system since it saved water and fertilizers, allowing to obtain yield comparable to that obtained with traditional techniques (22 t/ha, on average). The reduction of the NS concentration (50% of the fertilizer concentration) reduced plant growth and consequently the total production by 15%. The use of different substrates did not affect the cultivars productivity. Concerning quality, ‘Saporro’ plants produced a high percentage of pods in the category “Extra” than ‘Venda’ plants (92 % vs. 89%, respectively). Sand can be an alternative of perlite given that it costs 30 times less.