September has brought some much-needed relief from an unrelenting summer of extreme temperatures, marking the beginning of autumn. This transitional period has earned the nickname “veroño” due to the high temperatures, both minimum and maximum, that have prevailed. The region of Andalusia, already affected by a prolonged drought, has been even more affected by these adverse conditions.
In the context of the Gen4Olives project, which involves the monitoring of two rainfed olive grove farms in the region of Estepa, Seville, several episodes of rain have been detected. To carry out this monitoring, a leaf wetting sensor has been used instead of a traditional rain gauge. This device, which simulates a leaf, is equipped with internal electronics capable of detecting morning dew and, in the case of light rainfall, provides precise information on when it occurs.
During the month of September, rainfall events were recorded on the 2nd, 3rd, 14th, 15th, 17th and 22nd. The highest leaf wetness reading was obtained on 15 September 2023 at 17:42.
In contrast, the data collected by the nearest weather station indicate that 66 litres per square metre were recorded, while in the Seville countryside the figure was around 31 litres per square metre. These data are also collected by BrioAgro through its weather data feed, which not only shows past data, but also forecasts for the next 7/15 days.
Despite this rainfall, it is important to note that the moisture has hardly reached the deepest roots. In fact, the moisture in the shallow roots (at 20 cm depth) showed a minimal increase from the beginning to the end of the month:
- – Start of the month: 37.23 L/m³ (litres per cubic metre of soil)
- – End of month: 37.28 L/m³ (litres per cubic metre of soil)
In addition to the rains, the month of September already shows the reduction of sunshine hours, which went from:
- – Beginning of the month: 12.92 hours
- – End of the month: 11.82 hours
A decrease in the temperature at the roots, specifically at 20 cm depth, is also observed, from:
- – Start of the month: 29.03 °C
- – End of month: 24.75 °C
A minimum episode of 21.64 °C was recorded on the 23rd.
However, the humidity was barely noticeable at 40 cm depth, since, although it is greater than at 20 cm, it did not reach the amount necessary to increase the humidity at that point:
- – Start of month: 38.57 L/m³ (litres per cubic metre of soil).
- – End of month: 38.35 L/m³ (litres per cubic metre of soil)
In short, this “veroño” September was tempered by rain in Andalusia, although the humidity did not reach the deep roots, it did allow some respite for the final harvest.