Winter rains do not eliminate the risk of summer drought stress

Even though the water volumes received this winter and early spring have mostly replenished groundwater reserves, the risk of drought cannot be ruled out for crops already in place or those to be planted in the coming weeks.

The excess winter rainfall is not without consequences

Winter weather has resulted in delayed planting in most areas. This has inevitably led to less root development in plants, making them more susceptible to potential deficiencies and end-of-cycle water shortages. For plants that can be sown on time, another problem arises. Sown in waterlogged soil, they too could experience reduced root development. Satisfied with the amount of water available in the soil at time T, they then limit their root growth, a phenomenon known as “lazy roots.”

Differentiating RAW and survival reserve

The plant’s ability to draw water from the soil reserves depends not only on the species and the development of its root system but also on the soil structure. To understand the water dynamics of soils, two concepts are essential: the Readily Available Water (RAW) and the Survival Reserve. Combined, these two reserves form the Available Water (AW).

The RAW corresponds to the portion of the available water that a species can extract without reducing its transpiration, experiencing drought stress, or limiting its growth. It generally accounts for between 40 and 80% of the available water in a soil, depending on its depth and the cultivated species. In winter, rainfall primarily replenishes groundwater. Beyond the month of April, it is upon this reserve that plants must rely to ensure their growth.

According to the weather forecasts, for the next three months – from April to June – there are expectations of warmer air masses circulating over much of Europe. Regarding precipitation, it may remain fairly close to average for April and May but start to decrease in June. The initial trends for the July-August-September quarter suggest persistently higher temperatures than seasonal norms and below-average precipitation.

Phytosterols: Powerful Allies

The risk of water shortage is far from being eliminated. Especially since it takes very little to have consequences on yield. In corn, for example, a day of stress equates to a loss of 1 q/ha.

There are agronomic levers available to help plants better cope with these periods of drought : choosing more resistant varieties, adjusting planting dates, optimizing weed management, crop residue management, etc. But this isn’t always sufficient, and the outcome is not guaranteed.

The challenge is also to help crops better anticipate and combat this stress. The use of phytosterols proves to be very effective. When the plant is subjected to drought stress, its phytosterol content varies to regulate the opening of its stomata and thus foliar evaporation, stimulate root growth, and with it soil exploration. Hence the idea of researchers to provide this substance preventively via foliar application to prepare the plant for future water shortages. Elicit Plant has thus developed several solutions based on phytosterols: Best-a for corn, EliSun-a for sunflower, and EliGrain-a for spring barley, which, thanks to their unique active ingredient, allow for a 20% reduction in water consumption, resulting in an average yield gain of 10%.