Cope with droughts by improving the water-holding capacity of your soil

Organic matter fulfills many important functions in the soil. One of the functions is the ability to improve the water infiltration after rain and to increase the water-holding capacity of the soil. Good water management is highly important now that we are increasingly dealing with both droughts and extreme precipitation. Invest in the resilience of the soil and limit drought damage by investing in organic matter.

Europe is experiencing its worst drought in at least 500 years. In August 2022 more than half of Europe was affected by a deficit of soil moisture and crop yields are being significantly reduced (figure 1). What can we do to better cope with droughts and improve the water management of the soils? 

Figure 1: Soil moisture anomaly August 2022 (JRC Global Drought Observatory of the Copernicus Emergency).

To minimize the impact of droughts, the soil needs to capture rainwater when it falls and let it infiltrate, store as much of that water as possible, and allow plant roots to grow and enhance their underground biomass. All of these factors are improved by one vital factor of overall soil health; the soil organic matter content. Soil organic matter affects the chemical, physical and biological properties of the soil.

Soil structure

Both the organic matter content and the soil texture of soils influence water management. The soil texture can be defined by the percentage of sand, silt and clay particles. Clay binds water too tightly while sand does not bind water well enough. Silt particles are able to bind water and also release water when the crop is in need. While the soil texture is usually something that cannot be influenced, the organic matter can contribute to a good soil structure and water-holding capacity. It can ‘glue’ soil particles together that are therefore able to retain water longer. In clay soils, organic matter ensures better crumbling. The soil becomes ‘airier’ and will be able to let the water infiltrate more easily. Improved soil structure also benefits the root development of crops.

Water holding capacity

The more organic matter a soil contains, the better its water-holding capacity. This is because the addition of organic matter increases the number of micropores and macropores in the soil. Organic matter can hold 20 times its own weight in water while pure sand does not go beyond 0.2 times. It is estimated an increase of 1% soil organic matter, which equals around 0,5% soil carbon, can increase the water-holding capacity by 150.000 litres per hectare (fig. 2).  This increase in the water-holding capacity depends on the soil properties. However, organic matter always improves the water balance, in whatever type of soil.

Figure 2: Total litres of water stored in soil relative to soil carbon levels

Organic fertilizers

In general, the soil organic matter content can be increased in three ways:

  1. Improve the input of residues by altering the crop rotation and leaving crop residues.
  2. Increase the supply of soil organic matter by annually adding manure, compost and/or organic fertilizers.
  3. Reduce the de-composting losses by limiting disturbance of the soil.

It is always important to calculate an organic matter balance for each field. When more organic matter is removed by harvesting and broken down by soil organisms than added, the soil will gradually degrade over time. Additional organic matter can easily be applied by organic fertilizers. Organic fertilizers have on top of the nutritional value, a high effective organic matter content. The effective organic matter content is defined as the organic matter that is still available after one year after incorporation into the soil. MeMon provides a wide range of organic fertilizers for different types of crops and circumstances. Furthermore, organo-mineral fertilizers can positively contribute to the addition of organic matter compared to mineral fertilizers.

Improving soil health cannot happen overnight and is difficult to achieve while in midst of a drought. But managing your soil in good times can help reduce the impact of the next drought when it invariably comes.