Gardeners tend to think of the soil as something that has fixed properties. We test for soil pH, and we act as if the soil pH will stay the same all through the year unless we do something about it. We give our yards and our vegetable gardens potassium (K), but we fail to take into consideration that when we uproot a plant, we uproot the potassium inside it. We look for the phosphorus (P) content in the fertilizer we give our landscape plants and our vegetable crops but fail to take into consideration that weather affects how available it is.
Humic acid and humate buffer changes in pH, potassium, and phosphorus throughout the year. Providing your plants with humate can stabilize the soil to give you better results with lime and sulfur for pH management, and potash and phosphorus in ever-more-expensive fertilizers. In this article, we will tell you how the progression of the seasons affects these three vital aspects of horticultural management and what humate does to stabilize them.
Read more to learn: How Does Weather Affect Soil in Each Season?
Humic acids and soil pH through the seasons
Soil pH goes down every spring in well-fertilized soils.
Fertilizers provide nitrogen in the form of ammonia or ammonium compounds, a chemical combination of nitrogen and hydrogen. Enzymes in healthy soil convert ammonia into nitrates, a chemical combination of nitrogen and oxygen. This process releases hydrogen ions, which lower the pH of the soil.
The activation of nitrogen in the soil isn’t the only thing going on in your garden soil or in the dirt under your turf that lowers soil pH in spring. As the weather gets warmer, plants sink their roots into the soil. Roots don’t release oxygen through photosynthesis since they never see the sun. Instead, they release CO2, which reacts with the water in the soil to form carbonic acid, further lowering soil pH. Bacteria do the same thing.
In many locations, summer heat and drought cause salts to accumulate near the surface of the soil. These salts force hydrogen ions down into the root zone and lower soil pH even more.
The cumulative effect of the growing season changes can lower soil pH by as much as 1.0. If you start the growing season with a soil pH of 8, just growing plants and letting the soil dry out between watering sessions can lower the pH to 7 by the beginning of the fall. Prolonged drought prevents this noteworthy drop in soil pH, but heavy rains accelerate it.
All of this makes the benefits of liming the soil to raise its pH and broadcasting sulfur to lower pH highly dependent on the amount of nitrogen fertilizer you put out, and when. You can invest a lot of money and effort into changing soil pH and still not get the results you want, unless you add a buffer. The best buffer for your soil is humic acid.
Humic acid and organic matter keep the moisture levels of the soil more nearly constant. They absorb some of the carbon dioxide released by roots and healthy bacteria. They help you see the results you expect from lime and sulfur.
Humic acid and soil potassium through the seasons
Plants depend on potassium to regulate the flow of fluids. Plants deprived of potassium will wither and die. But because every cell in a plant uses potassium, the amount of potassium in your soil varies drastically between planting and harvest.
Cutting off all the aerial parts of a plant to harvest it, like cutting lettuce and leafy greens, or hauling away grass as hay, takes potassium out of the landscape forever. Only in situations like cutting your grass with a composting mower give your soil a chance to recover the potassium it sends to growing plants.
Potash is something many gardeners and landscape managers simply must give their plants every season. But humic acid also helps in this situation.
Potassium is transformed into its ionic form by the action of enzymes released by soil fungi and the tips of roots. Humic acid products react with moisture in the soil to produce colloids that transport these potassium ions to the root tips that need them.
Humic acid and soil phosphorus through the seasons
Phosphorus levels in the soil show an unusual pattern of season variation in row crops. All spring and all summer, phosphorus levels get lower and lower in the soil directly beneath the plant in the row. If you keep up with your cultivation, they don’t fall in the soil between the rows.
This leaves considerable phosphorus in the soil for next year’s crop. Just till the soil. But you will have more residual phosphorus when you treat the soil with humic acid or humates.
Humic acids stabilize phosphorus in the soil, so the phosphatase enzymes in the fungal mycelia of loose soil can release it into a form plant roots can absorb. The more humic acid there is in your soil, the more phosphorus is available for this complex, symbiotic relationship between plants and soil.