Cumulative effect over five years of deficit irrigation on peach yield and quality

Many research studies have shown the effect of irrigation restriction on peach annual fruit growth and production. This paper presents results obtained over five years. The work was carried out in a commercial orchard near Tunis. Drip irrigated 4-year old trees of the late cultivar 'Carnival' planted at 3x6m spacing were used. The local climate is a Mediterranean type with 450 mm annual rainfall and hot dry summers. Experimental treatments consisted of four irrigation regimes. With reference to the control, water was reduced during early fruit growth (Phase I&II), late growth (Phase III) and all stages. Restrictions consisted of 33% less irrigation water. Penman-Monteith reference evapotranspiration (ETo) was used to scale the applied restrictions. Total water supply from precipitation (P) and irrigation (I) was monitored over the different growing stages. Typically, the ratio (I+P)/ETo increased for the control from 0.65 to 1.05 during the period of fruit set to the end of phase III. Yield reductions varied between 0% and 34% depending on the year and treatment. The greatest decrease was observed for water reduction during Phase III. However, the continuous restriction gave the highest yield of the three treatments with water restriction. Fruit size varied in a similar way as yield. Total dry matter and sugar content showed improvement with increasing deficits.