Soil management affects yield components of young olive trees under deficit irrigation

We compared vegetative growth, fruit characteristics and yield components of young olive trees (Olea europaea L. 'Frantoio') grown under either shallow tillage (ST) or permanent grass cover (GC) in a sandy-loam soil over four years. The soil was tilled from the year of planting (2003) until October 2004, when both soil management treatments were established. The ST treatment was kept weed-free by disking (about 0.15 m depth), whereas the GC was obtained by letting the natural flora grow. Trees were fully irrigated until year 3 after planting, when deficit irrigation (about 50% of full) was started for both soil treatments. Trunk cross sectional area (TCSA) of GC trees was 74 and 83% that of ST trees at the end of the 2006 and 2009 growing seasons, respectively. Fruit yield and oil yield of GC trees were 60 and 66% those of ST ones, respectively; however, when expressed on a TCSA basis, they resulted 85 and 94%, respectively. Yield components were differently affected by soil management. The number of fruits of the GC treatment was significantly lower than that of the ST treatment. The oil content in the mesocarp was similar for both treatments. Differences in fruit weight and pulp/pit ratio between treatments were likely due to the crop level rather than soil management practices.