Soil fertility basics in 10 bullets

Shankar Venkataraman
4 min readDec 27, 2020
Healthy broccoli

I want to summarize how a farmer must improve his soil fertility in 10 bullets. There is a lot more to this work but here I try ten bullets to simplify things.

  1. 100 grams of soil with a Cation Exchange Capacity (CEC) of 1 will have all its cation exchange sites (negatively charged sites) occupied by (adsorbed) by one milligram of H+ ions.
  2. 20 milligrams grams of calcium for example(atomic weight 40 compared to atomic weight one of hydrogen) will occupy those same sites in 100 grams of soil with CEC of 1. Ca++ has 2 positive charges.
  3. If 100 grams of soil had a CEC of 3 it will take 3 milligrams of H+ to occupy those locations. Higher the CEC and AEC of soil, the better the soil fertility.
  4. Clay in the soil has higher CEC than Silt and Sand. Different humic substances can have CEC in the hundreds. So CEC is like a container filled with charges. If the soil has more clay and more humus, it can store more mineral ions. Both cations and anions and will not be washed away by rain or irrigation water. Humus has a much bigger role to play than just Total Exchange capacity. Humus is the very basis of healthy soil. Humus is different from soil organic matter. If soil management is not proper, humus formation will not happen.
  5. Some of the many jobs of Microbes in the soil are to extract mineral ions from the soil, and consume the root exudates of plants, and multiply in numbers. But even microbes are consumed by plant roots and compounds made by microbes called microbial metabolites are taken up by plant roots from the soil and not just mineral ions. The association of plant roots and soil microbial life is extremely complex. Very little of what happens in the root zone (rhizosphere) is well understood. But that is sufficient to give us a lot of data, particularly the truth that without healthy soil<=>microbes<=>plants interaction, peak human health is not possible. Through wrong practices, a farmer can destroy this very balance and destroy the soil. Ultimately life will continue on the planet but we will not if we continue destroying our soils. Microbes also fix nitrogen from the air and do many complex roles that are areas of research and analysis.
  6. The ions extracted by microbes are stored in ion exchange sites. But if there are no additional sites to store them, the ions will be washed off from the soil by rain or irrigation. The farmer must create ideal conditions for soil humification to happen. One way to do that is to grow a mix of cover crops — legumes+pulses+oil seeds+grasses. This is another area of study and application.
  7. Tilling the soil destroys microbial balance and oxidizes the carbon in the soil. But if the soil is compressed (compacted), it needs to be tilled gently to expose it to air. The Calcium<=>Magnesium balance is very critical for healthy soil. It needs to be in the range of 68:12 base saturation rate of the cation exchange sites. The equipment used for plowing is important such as a broadfork or a chisel plow that does not destroy soil life. If the soil has extensive fungal networks, even using a chisel plow will also destroy that. A no-till seed drill or a broad fork is the only option in such a case. Soil management has to be understood deeply. Exposing soil to too much sun and rain alters soil balance. Protective structures like shade nets or greenhouses can be considered from time to time but soil also needs regular exposure to natural elements of gentle sun and gentle rain. It's critical to add the right compost and minerals to the soil after doing a biology test of both soil and compost and a chemistry test of both soil and compost. Without looking at test reports, a farmer is guessing and that is blindness. Without making compost and testing it, the farmer will not get very far with farming. There is no religion or bias in farming. Science and data is the only truth.
  8. Irrigation water can have a strong impact on soil fertility and balance. It's important to ensure the irrigation water has no carbonates, no chlorine or chloramine, no heavy metals, no salts. So the Agriculture water must be tested and proper filters must be installed to ensure the water we use for irrigation does not alter the fine balance in the precious soil.
  9. Balance of nutrients in the soil is more important than availability. Its possible that minerals in soil may not get into the plants and sap and tissue tests must be done in specific cases. Foliar feeding with organic mineral sources is recommended as well in specific cases. The very weeds and plants in your farm are the mineral sources. Through specific Korean Natural Farming methods, you can extract the minerals from the weeds growing on your farm and foliar feed it to your plants.
  10. Photosynthesis is the engine behind soil fertility. Every effort must be made to improve photosynthesis efficiency from 20% to 40–60%. This has a huge impact on soil life as the plants can store more food in the soil for consumption by soil life.

The farmer needs to care about the above 10 bullets. There is a lot more than these 10 bullets above. But these 10 can be called basics or the first step in understanding soil fertility. Farming is deep work. A farmer cannot distract himself and take the work lightly. The results of farming will be according to the depth of the work done by the farmer. In his hands are the health of his customers, the health of the soil. So it's a great responsibility.

Shankar @bhoomifarmers



Shankar Venkataraman

Farmer, author, farming teacher, public speaker. Areas of Agriculture and technology in Agriculture.