Effects of irrigation regime on yield and quality of processing tomato (Lycopersicon esculentum Mill.) cultivars.

Results of a two-year research carried out in 1992-1993 at ‘Gaudiano' (41°03’N, 15°42’E in Basilicata region, Southern Italy) in Ofanto Valley with the aim of evaluating the influence of different irrigation regimes on yield and quality characteristics of processing tomato, are reported. Four irrigation levels, i.e. unirrigated control and restoration of maximum crop evapotranspiration (100 % of ETc) for each year; 66 and 33 % of ETc only for the first year, and 50 % of ETc and supplementary irrigation (whenever the soil water potential dropped below -1.5 MPa) for the last year, were applied on three cultivars of processing tomato (‘Centurion’, ‘Amur’ and ‘Brigade’). During the two years the highest marketable yield were obtained with maximum restoration of ETc, 51 and 79 t ha-1 respectively in 1992 and 1993; consequently yield increasing was 225 and 1327 % respect to unirrigated control. The cultivars ‘Amur’ and ‘Brigade’ yielded more than ‘Centurion’ in the first trial; in 1993 ‘Brigade’ was the most productive cultivar in watered treatment with restoration of 50 % of ETc; ‘Amur’, on contrary, in the most irrigated regime. Quality traits were also influenced by irrigation regime; in fact, in 1992, dry matter content of fruits ranged from 7.6 % in unirrigated control to 5.9 %, as average, with restoration of 66 and 100 % of ETc. In 1993 fruit dry matter content was 8.7 % without irrigation, 4.3 % with the maximum of ETc restoration, and 6.1 %, as average, with restoration of 50 % of ETc and with supplementary irrigation. Soluble solids content was 9.2 - 7.2 - 6.4 and 4.6 °Brix respectively in unirrigated control, with supplementary irrigation, and with restoration of 50 and 100 % of ETc. Juice fruit content in the second trial was higher (93 % as average) with supplementary irrigation and restoration of 50 % of ETc than without irrigation and with the restoration of 100 % of ETc (90 %). ‘Brigade’, in two years of research, showed the highest quality of fruit because of size, dry matter and soluble solids content.