A drastic decrease in humus content has begun to be apparent in a large part of Polish soils. Studies show that in the last decade, the humus content has decreased by as much as 30%. A deficit of natural fertilizers and simplified crop rotation have systematically made this problem worse. Every farmer who thinks about maximizing profits, and at the same time is aware of what is happening to his soil, should think about how he can restore humus in his soil, or at least change the humus balance in the soil to a positive one. The humus content of a soil has a very significant impact on its structure and the amounts of water and main nutrients in it.
With the current climate changes and the distribution of rainfall in our country, we are regularly faced with shortages of water during periods that are critical for plant growth. Short-term autumn and spring droughts have become a rule, making it impossible to take advantage of the yield-forming potential of particular species and cultivars of crop plants.
The table below illustrates how the humus content affects the storage of water in the top layer of soil (down to 30 cm).
| Organic matter content | Water storage capacity |
| 0.50% | 80,000 L |
| 1.00% | 160,000 L |
| 2.00% | 320,000 L |
| 3.00% | 480,000 L |
| 4.00% | 640,000 L |
| 5.00% | 800,000 L |
It is worth knowing that one unit of humus has a sorption capacity that is several hundred times greater than the same unit of mineral matter. Humus also has a significant impact on the formation and maintenance of the aggregate structure of soils. Humus is also the main store of organic nitrogen. In the table below, we can read how the humus content influences the nitrogen retention capacity of the soil.
| Organic matter content | Nitrogen retention capacity |
| 1.00% | 2,400 kg |
| 2.00% | 4,800 kg |
| 3.00% | 7,200 kg |
| 4.00% | 9,600 kg |
| 5.00% | 12,000 kg |
It is worth knowing that humus is a composite of complex organic compounds whose composition is very different from the starting product. These compounds are formed in the soil from organic decomposition products in the process of synthesis under the influence of soil microorganisms. That is why it is so important to provide the soil with not only humus but also a positive bacterial microflora, which will release organically bound nutrients and accelerate the decomposition of organic matter lying in the soil, e.g. after combine-harvesting cereals, and create humus in the soil.
Damian Gawroński, M.Eng.
