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Universidad de Córdoba (2018)

Almond response to irrigation : Deficit irrigation and water production function

López-López, Manuel

Titre : Almond response to irrigation : Deficit irrigation and water production function

Respuesta de la producción al riego en almendro : riego deficitario y función de producción

Auteur : López-López, Manuel

Université de soutenance : Universidad de Córdoba

Grade : Doctoral Tesis 2018

Almond is becoming a very extended tree crop in Spain, due to good prices in the last years and likewise good market perspectives. A fast intensification process is taking place ; new plantations (of which the acreage has doubled from 2014 to 2016) have nothing to do with the traditionally marginal rainfed crop producing around 150 kg/ha. Instead, taking after the Californian scheme, some of them are sited in deep and fertile soils, receive much less pruning and more inputs for nutrition and crop protection, and are usually irrigated. However, water availability is lower here in Spain than in California or Australia, where irrigation allocation for almond is about 12,000 m3·ha-1. On the other hand, rainfall is somewhat higher in Spain. In addition, breeding programs have led to self-fertile and hard-shelled cultivars in Spain whereas self-incompatible and soft-shelled ones, such as Nonpareil, are more common in California. All these differences have generated a need for information about irrigation requirements of intensive almond orchards in our conditions. Research content In the present thesis, first, maximum crop transpiration (T) was measured by both a large weighing lysimeter and calibrated sap-flow probes, concluding that mid-stage transpiration coefficient (KT) of a fully mature almond orchard (covering 85% of soil) should be around 1.04, but could be affected by high fruit loads. Measuring transpiration instead of evapotranspiration (ET) made our findings more easily transferable throughout different conditions, despite different irrigation management alternatives (for instance, one or two drip lines, or microsprinklers ; the three of them presenting different soil wetting patterns). Then, we conducted water balance (WB) measurements on both fully and deficit irrigated (DI) almond four-trees-subplots, to get a relation between irrigation (IR) regimes and actual water use (ETa). Evaporation from soil (ES) was modelled and detracted from evapotranspiration to calculate transpiration values. This method was compared to direct transpiration estimates from sap-flow. Conclusions Almonds were found able to consume up to 200 mm from the soil reservoir and to extract water from deeper than 2 meters. Finally, kernel yield and its components (fruit load and kernel unit weight) were related to all three, irrigation, evapotranspiration, and transpiration, thus establishing the water production functions for almond. Irrigation water marginal productivity (IWMP) ranged from 0.33 kg·m-3 in the most severe DI treatment to 0.11 kg·m-3 in the full irrigated treatment. Présentation

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Page publiée le 12 février 2019