This study aims to determine the relationship between laboratory frost-resistance data for the leaves of eight olive cultivars and observed field resistance in the same genotypes undergoing natural frost damage. The lethal freezing temperature (LT50) for each cultivar was established by measuring the electrical conductivity (EC) of the medium into which solutes from damaged leaf tissue were leaked. The value obtained was then correlated with percentage frost shoot for the same eight cultivars damaged by natural frosts in a field test. A negative correlation was observed between the percentage frost shoot and leaf LT50 for all the cultivars under study. The most frost-hardy cultivars (`Cornicabra', `Arbequina', and `Picual') were those presenting the lowest percentage frost shoot and lowest LT50. Conversely, the most frost-susceptible cultivar (`Empeltre') displayed 100% frost shoot, together with one of the highest LT50 values (–9.5 °C). According to these results, lethal freezing temperature (LT50) calculated from leaf ion leakage at a range of freezing temperatures, seem to be a valid parameter for evaluating frost tolerance in olive cultivars.

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Developing an appropriate irrigation schedule is essential in order to save water while at the same time maintaining high crop yields. The standard procedures of the field evaluation of distribution uniformity do not take into account the effects of the filling and emptying phases of the irrigation system. We hypothesized that, in sloping sandy soils, when short drip irrigation pulses are applied it is important to take into account the total water applied from the beginning of irrigation until the emptying of the irrigation system. To compute distribution uniformity, we sought to characterize the filling, stable pressure, and emptying phases of a standard strawberry irrigation system. We found that the shorter the time of the irrigation pulse, the worse the distribution uniformity and the potential application efficiency or zero deficit are. This effect occurs because as the volume of water applied during filling and emptying phases increases, the values of the irrigation performance indicators decrease. Including filling and emptying phases as causes of non-uniformity has practical implications for the management of drip irrigation systems in sloping sandy soils.