Humic substances to improve the potato harvest

Potatoes are one of the world's essential staple foods. They are the fourth most cultivated crop after rice, wheat and maize. Their ability to adapt to different conditions makes it possible to cultivate them almost everywhere. However, extreme climatic conditions such as prolonged periods of heat and, most recently, a wet growing year have severely affected the potato industry and reduced crop yields. Also problematic is the increasing soil salinisation caused by incorrect irrigation techniques and mineral fertilisation, which is further damaging the popular tuber. Practical solutions are required, ideally ones that can be implemented quickly and effectively.

The nature of the soil is crucial for the growth of the tuber

Potatoes thrive in nutrient-rich soil. A soil with a high humus content and a well sieveable structure that allows a balanced distribution of moisture promotes high yields. If the soil is too loose, the water supply is impaired and the potatoes are susceptible to scab. On heavy soils that warm up slowly in spring, lumps form and this often leads to deformation of the tubers.

Using humic acids and new varieties to combat salt stress in the soil

However, there are approaches to combat the problems of salinisation. In Egypt, experiments with the humic acid-based product POWHUMUS® showed impressive results: The crop yields per plant and the average size of the potatoes increased significantly. In addition, in contrast to the control group, the leaves of the treated plants showed no external signs of stress, such as typical yellow salt edges.

The humic acids obviously help to alleviate salt stress. The mechanism behind this is based on the high cation exchange capacity of humic acids, which break down salts in the soil, chelate their cations such as calcium and manganese and make them available to plants in the vicinity of the roots, thereby significantly reducing the harmful salt concentration.

In addition to soil treatment, researchers on the Dutch island of Texel are trying to counteract salinisation with new varieties. The potato plants there are sprayed with salt water. Varieties that do not tolerate this are discarded, while the others are investigated further. The results are promising: the tubers that prove to be salt-tolerant could represent a significant solution for affected cultivation areas. Egypt and India have also already signalled their interest in cooperation.

Healthy tuber growth requires a sufficient supply of nutrients

Humic acids also have a strong effect on sandy or heavy soils that are not extremely salt-loaded, as they improve both nutrient uptake and soil structure. This increases the efficiency of fertilisers while at the same time reducing leaching. Treatment with humic acids is advisable shortly before sowing the seed tubers. This allows the young tubers to meet their increased nutrient requirements and root through the soil faster and more effectively. The humic acids optimise the carbon-nitrogen ratio directly at the seedling and create a kind of organic nutrient store. The earlier yield formation begins in early summer, the less relevant damage caused by late blight will be later on. Immediately after planting the tubers, the supply of phosphates is particularly important. Humic acids bind the phosphorus in the soil near the roots and thus ensure an optimal supply.

The prospect of future summers with long periods of heat and drought is not good news for the potato industry. Especially during the tuber filling and starch formation phase, heat and drought can cause problems. In soils that are too dry, many essential minerals are present in undissolved form, which makes it difficult for the potatoes to absorb them - often with serious consequences for plant growth. Humic acids can also play a decisive role here by making these minerals available to plants and thus ensuring yields even under hot and dry conditions.

Humic acids serve as soil conditioners and stimulate the growth of potatoes.

Humic acids do not act directly as nutrients for the plants but activate the beneficial soil life around the potato tuber. The use of products such as POWHUMUS® or LIQHUMUS 18® improves the storage of essential nutrients in the crop. This improves yield, promotes leaf health and root growth. The storage of starch in the potato tuber is increased and the potatoes utilise their genetic potential more effectively. It is therefore acceptable for the farmer if the salt content is higher at the beginning or if the soil is heavy or light. The use of humic acids can facilitate cultivation under difficult conditions and help to improve unfavourable soil conditions in the long term.