Sandy soils have almost the opposite problems of clay soils. That would stand to reason, as clay soils are made up of very small particles and sandy soils have larger particles. Particle size makes a huge difference in the way water, air and nutrients move through the soil. Large particle size of sandy soil particles mean that water moves fast and nutrients leach (move away, into groundwater) quickly. Humic acid added to sandy soils will dramatically improve sandy soils soil for gardening and farming purposes. Unless you are using pure sand as a hydroponic growing medium, you need a bit more organic matter in your soil. Humic acid can help.

Humic Acid and Nutrient Availability in Soils

Sandy soils, in general, have a dearth of organic matter. Organic matter is important in soils for numerous reasons. Of chief importance regarding organic matter in soils is that as it decomposes, it breaks down into nutrients the plants can absorb. The sand particles in sandy soils also weather and break down, but do not release the same nutrients as organic matter. Humic acid also aids in nutrient holding capacity for sandy soils. Without additional organic matter, sandy soils are unable to hold on to nutrients so that they remain available for plants. The nutrients leach (or leave the soil). If you see plants growing on sandy soil without enough organic matter added, they often show signs of nitrogen deficiency (a yellowing of the leaves.) In addition to making macronutrients more available in the soil, humic acid also makes micronutrients such as iron more available, by bonding with it and keeping it from forming precipitates with phosphorous and leaching out of the soil.

Humic Acid and Soil Structure in Sandy Soils

Another way that humic acid improves sandy soils is by adding structure. In sandy soils without enough organic matter, the spaces between soil particles are large and generally uniform. While that makes it easy for plants to grow roots, it also allows water to drain fast. Sandy soils need additional organic matter to form spaces for water to stay in the soil. Humic acid is beneficial to the microorganisms that decompose other organic matter. Adding this substance to sandy soils will increase soil microorganism populations, resulting in the soil's ability to maintain its health over time.

Humic Acid is the Duct Tape for Gardeners

It sounds too good to be true—the same substance that helps break up clay soils and improve drainage and oxygen exchange also helps sandy soils retain nutrients and water. Many chemicals have been developed from the beginning of agriculture, but none can rival organic matter, especially humic acid. Research by different organizations has identified benefits of humic acid in terms of soil microbial activity, plant growth and respiration, nutrient availability in soil, and more, but no researcher has been able to exactly mimic the effects of naturally occurring humic acid with any synthetically produced substance. There is simply no substitute.