Irrigation Scheduling Optimisation in Olive Groves

Introduction: The diffusion of irrigation in olive orchards requires accurate scheduling of the application of water.

Objectives: To evaluate the efficiency of different modes of irrigation scheduling for mature olive trees grown at different plant densities and in different soil types and irrigated under different systems and strategies.

Methodology: We compare the irrigation scheduling with variable quantities and intervals (OPT), optimised by the water balance-evapotranspiration method (WB-ET) by evaluating the use of variable quantities and different fixed intervals (3, 7, 14 and 28 days) as well as a fixed interval and quantity (FIX). These scheduling scenarios were applied to high-density and super-high density groves in medium to fine textured and moderately coarse to medium textured soils irrigated by sprinkler, microjets and drip irrigation systems under full and deficit (sustained, SDI and regulated, RDI) irrigation strategies in a Mediterranean environment (Calabria Region, Italy). Three sets of measured meteorological data (2016, 2017 and the mean values of the 2001-2017) were used for simulations.

Results: OPT scheduling showed maximum efficiency. Three-day and weekly intervals show acceptable performance in terms of efficiency as well as water and energy requirements, whereas FIX scheduling shows very low efficiency. SDI and RDI permit mean savings of approximately 36%-54% of water and energy compared to full irrigation. High-density orchards drip irrigated under the SDI strategy show minimum water and energy requirements.

Conclusions: The traditional irrigation strategy at fixed quantity and interval is not adequate to achieve high efficiency in the irrigation of olive orchards, from both the agronomic (reduction of crop water stress) and economic (reduction of water and energy requirements) point of view. The optimisation of the irrigation scheduling requires the estimate of the water quantity to deliver in each irrigation in both the irrigation management at variable and fixed interval. The WB-ET model is an efficient and (relatively) simple tool to foresee the quantities and the dates of irrigation during the irrigation season.