The heat is slowing down the ripening of the crop

The hot, sunny weather that has settled over Luxembourg is having a mixed impact on the agricultural sector, forcing farmers to strike a balance between reaping the benefits of the sun and protecting their crops from heat stress. As fruit and vegetable grower Jean-Claude Muller from the commune of Contern explains, moderate heat stimulates growth, but excessive heat and sudden temperature fluctuations pose serious problems for delicate crops. Some varieties tolerate high temperatures much better than others. For example, lettuce, which barely grew during the May cold snap, is now showing vigorous growth.

At the same time, for other crops, global warming poses hidden risks. Müller cites apple orchards as an example, where flowering has only just finished and the critically important stage of fruit cell division has begun. Unfavourable temperatures during this period can significantly slow down biological processes, preventing the apples from reaching the necessary weight and density. Conditions can only be described as favourable as long as the thermometer does not exceed +35–36°C, although growth retardation in many plants is already observed once the temperature crosses the +30°C threshold.

For this reason, farmers welcome the weather forecasters’ predictions of a drop in temperature, as this will help minimise damage to the crops. However, a cooling trend is traditionally accompanied by an increased risk of thunderstorms. Sudden changes in the weather are highly undesirable in vegetable and fruit growing: despite the high water requirements of crops, severe storms and, in particular, hail can completely destroy ripening fruit. The optimal scenario for farmers is for the weather to stabilise at just below +30°C, which is important not only for the plants but also for staff forced to work outdoors in extreme heat.

To protect their staff, farms are bringing forward the start of field work to the early morning, when it is still cool, and suspending activities during the hottest hours of the afternoon. Soil desiccation presents a further challenge. When the soil becomes hard and dusty, standard irrigation proves insufficient. Effective water management during this period requires the mandatory mechanical loosening of the soil using hoes. 

This process not only eliminates weeds but also breaks up the surface crust, allowing oxygen to penetrate. Such treatment disrupts the capillary action in the soil, slows down moisture evaporation and ensures that water reaches the plants’ root systems. Watering dry, compacted soil without first loosening it is pointless, as the moisture simply spreads across the surface and evaporates instantly. The development of weather conditions over the coming weeks will be a decisive factor in determining the volume and quality of the summer harvest.