Effects of the number of drip laterals on yield and quality of apples grown in two soil types

The effects of water distribution patterns in drip irrigation on fruit production and fruit quality were evaluated during two seasons in two commercial orchards of Gala Brookfield apple trees, grafted on M.9 dwarf rootstock. Research was conducted at El Manzano farm, with a clay-loam soil irrigated three times per week, and in Santa Mercedes farm, with a stony loam soil irrigated daily. Both farms are located in the Central Valley of Chile. The farm irrigation system was modified to establish three treatments which differed in the number of drip laterals per row (one, two and four), with 4.0, 2.0, and 1.0 L h−1 emitters spaced at 50 cm in both farms, respectively. All treatments received the same amount of water per week in each farm, based on the technical criteria of the farm advisor. Applied water in each farm was compared against the water use estimated by the AQUASAT platform. In the clay-loam soil, the volume of applied water was similar to the AQUASAT estimate. However, in the stony loam soil applied water was less than that estimated by AQUASAT. The results showed significant differences in production among treatments which varied only in the volume of wetted soil. The best results pooled over the two years were obtained with one lateral per row (T1) in the clay-loam soil (yield of 59.3 t ha−1), and with four laterals per row (T3) in the stony loam soil which yielded 50.8 t ha−1. Higher yields were associated with a tendency of greater fruit numbers per tree in both farms. Fruit quality requirements for export (equatorial diameter > 60 mm, weight > 90 g) were achieved but not the firmness in the second season at the stony loam soil, due to an irrigation deficit. Our results in apple emphasize the need to wet sufficient soil volume under drip irrigation, regardless of irrigation amounts, in light textured soils in particular.Authors thank the project ANID/FONDAP/15130015: Water Research Center for Agriculture and Mining (CRHIAM), and Department of Water Resources of the Universidad de Concepción, Chile