Basic Knowledge in Agriculture #63
In the past, I actually believed that soil leaching was merely about rain or irrigation draining water through dirt, but I understand it's not as simple as that.
What is Soil Leaching?
Soil leaching is when rainwater or irrigation water is absorbed into the soil and moves through the soil profile carrying minerals and nutrients down, some of which will eventually become inaccessible to plant roots after leaching and will be stored in aquifers.
The soil at my cousin's farm in Kumasi is sandy, which was an interesting realization for me, because after fertilizing the plants, I would go back two weeks later to notice they looked unhealthy and unfertilized. Obviously the sand did not have any holding capacity, so anything added to the soil would have quickly washed away. If it was clay soil, it would have held nutrients for much longer because water does not move through them as fast. Too much clay soil will prevent the soil from draining properly, which would most likely lead to waterlogging. It can be detrimental to the plant there.
The Factors influencing Soil leaching
The rate of rainfall is an obvious factor affecting soil leaching. Heavy rainfalls will undoubtedly increase the rate of leaching and nutrient depletion from the soil. For this year it hasn't been too much heavy downpour, well I can only say that for Accra, don't know for the rest of the country.
Different types of nutrients also leach from the soil at different rates. One important plant nutrient is nitrogen and it's highly leachable compared to potassium or phosphorus. I am not entirely sure how the pH of the soil impacts soil leaching but it's an easy search I can do on Google to find out. But what I do know is that pH has something to do with how tightly nutrients are held to soil particles.
What is the impact of soil leaching?
The overall impact of soil leaching is the depletion of nutrients in the soil. So in a situation where soil leaching happened intensely for your farmland, you must continue applying more fertilizer, which will cost more money so financial or problems could be considered another impact.
It doesn't just impact the farmer because if these nutrients reach our water supply, the result could be excessive algae growths, and we'll be getting less quality drinking water.
For my cousin's farm, mulching heavily and planting cover crops during the off seasons have helped reduce the occurrence of soil leaching.