Bio-agronomic effects of net shading on ‘Primosole’ mandarin

A study was carried out in Eastern Sicily on bio-agronomic effects of shading, with black and white net, young 'Primosole' mandarin plants compared with unshaded trees as control. In each treatment during 1999 the following parameters were recorded: air and soil temperature, difference of temperature between canopy and atmosphere (ΔT), photosynthetically active radiation (PAR), CO2 exchange rate (CER), transpiration rate (TR), xylem potential (Ψ), water use efficiency (WUE = CER/TR), quantum yield (QY = CER/PAR), fruit-set, shoots and canopy growth, area and leaf color and N, P, K contents in the leaves. Data showed that: - shading with black net, compared with the control, caused a PAR reduction of approximately 70%, lowered air, soil and leaf temperature and increased Ψ, CER, WUE and QY; - shading with white net reduced PAR by about 30%, and created opposite effects for all the other parameters, i.e. higher values of air, soil and leaf temperature and lower of Ψ, CER, WUE and QY. Plants shaded with black net showed higher vegetative growth, larger and darker green leaves, but under this light condition lower flower production yielded less fruits than the control.