Effect of nutritive solution K:N and shading on the “fruit”quality of NFT-grown strawberry.

We report the results of research carried out in Campania in 1995/96 and 1996/97 with the aim to investigate the “fruit” quality of strawberry grown with the NFT. Comparisons were made of eight electrical conductivity (EC)- levels (1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4 mS•cm-1) of the nutritive solutions, in factorial combination with crops arranged in pairs on double vertical layers; a control crop was managed traditionally. All the parameters attained the highest values with the upper crop layer, except for nitrates and pH which did not vary in relation to the plant position. Within the EC treatments, the dry and optical residues together with the sugars and the titratable acidity showed an increasing trend from 1.0 to 2.4 mS•cm-1; within the acids, citric and succinic increased very gradually while malic did not change. All the analysed macronutrients attained increasing “fruit” concentrations up to the 2.4 mS•cm-1 treatment whereas micronutrient contents were generally highest within the range 1.8-2.4 mS•cm-1. Dry and optical residues and sucrose values recorded with hydroponics in the upper level were significatively higher than those found in the control “fruits”, whose contents of glucose and fructose were lower referring to the highest salinity levels; by contrast, the acids were more highly concentrated in the control berries. Nitrates, calcium, magnesium, chloride, iron, copper and zinc accumulated in larger amounts in the “fruits” obtained with the traditional technique, whereas the control contents of phosphorus, potassium and sulphur were intermediate with respect to the 1.0-2.4 mS•cm-1 EC range. Compared to the lower crop layer, the values of dry and optical residues and sugars of the control “fruits” generally fell in the middle of the levels obtained with the tested EC range. The contents of acids and mineral ions were often highest in the control “fruits”.