Soil water content monitoring as a tool for sustainable irrigation strategy in a kiwifruit orchard under semi-arid conditions

In recent years, the cultivation of kiwifruit in Italy has spread to the southern regions. Drought and waterlogging are abiotic stresses causing yield uncertainty in various crops including kiwifruit. Kiwifruit water requirements depend on site-specific conditions (e.g., evapotranspiration demand, cropping system, cultivar, soil water holding capacity). An optimum irrigation strategy is desirable in kiwifruit to promote root turnover and encourage the uptake of essential mineral elements from the soil, to positively affect fruit development and quality. The aim of this 2-year study was to define a sustainable irrigation strategy based on a daily soil water balance of the soil volume wetted by irrigation integrated with soil moisture measurements to ensure soil moisture ranging within the readily available water (RAW) and field capacity (FC) interval. The experimental trial was conducted at a 5-year-old kiwifruit orchard (Actinidia chinensis) trained to pergola in the Metapontino area (with an annual water deficit of approximately 700 mm). The daily soil water balance was computed based on evapotranspiration (ET0) and crop coefficient (Kc) ranging from 0.5 (initial growth stage) to 1.1 (July, growth stage). Soil water content was measured at three depths (20, 40, 60 cm) by soil moisture sensors. The irrigation volumes applied were adjusted weekly to maintain soil water content in the two layers 0-30 and 30-60 cm of soil at 60-90% of FC, avoiding drought or waterlogging stress. The sustainable irrigation strategy that integrated the daily soil water balance with soil moisture measurements saved approximately 1,500 m3 ha-1 compared with the total water volume suggested using only the soil water balance. Results revealed that a timely soil water content monitoring is needed in order to support the sustainable irrigation strategy and to meet crop water requirements.