6 Steps to Turn Clay Soils into “Black Gold”

Soils in southern California are predominately clay. Great for making pottery but terrible for supporting plant life. Because of its small particle size, clay becomes easily compacted, and thus drains slowly or not at all. Also, clay soils prevent air from reaching the roots, which slows plant growth and retards microorganism growth.

Recipe for “Black Gold”
Prepare the planting hole by adding a teaspoon of bugs, a handful of 2,000 year old moss, and some decomposed plants and animals. Nothing is more important than soil preparation to ensure that your plants and trees take-off like a rocket and remain healthy throughout their life cycles. By careful preparation of the planting holes it is possible to create a perfect growing environment for plants and trees.

The goal is to break up and loosen earth that has become compacted. Replenish it with un-compacted soil rich in minerals, nutrients, and superior water holding capacity.

The 6 part recipe for “Black Gold”:
1. Add Gypsum for Drainage:
Most all of southern California have soils high in clay. These soils do not drain well and are high in alkalinity. Clay soils are tiny mineral particles that are less than 0.002 millimeters in size and have an electric charge that is negative. The negative charge makes positively charged minerals like iron, phosphorus, and potassium stick to them. This sticky nature makes clay soils high in mineral content.

The problem with too much clay in the soil is excess sodium. Sodium in clay acts like glue, binding particles together and inhibiting water flow. In addition because clay particles have an electric charge, they act like a magnet pulling the particles together via a strong magnetic bond. These sticky, bonded particles keep water from draining.

Clay soils need gypsum at installation, and every two years thereafter. Best to put gypsum in the bottom of each planting hole and work it into the soil on the bottom of the hole before planting. Adding gypsum to clay soils results is a chemical exchange. The gypsum releases calcium which takes the place of the bonded sodium stuck to the clay particles. This process loosens the soil by breaking apart theses tightly bonded particles.

2. Add Peat Moss amendment:
Peat moss is a natural, organic soil enhancer that has several benefits which include:

Water Absorption: Peat moss swells to 20 times its weight in water and then slowly releases its stored water to plant roots. This allows plants to have a steady supply of water over a longer period of time, resulting in reduced water usage.

Reduced Mineral Leaching: Peat moss reduces the amount of nutrients which bypass the root zone. The Peat Moss amended soil retains water and nutrients within reach of the roots, reducing the need for excess fertilizer.

3. Add Humus amendment:
Humus gives the soil the ability to absorb and retain moisture. Such soils do not dry out and require significantly less irrigation. Humus also provides a reservoir for the plant nutrients available to the roots system.

Humus plays a part in supporting soil bacteria, such as rhizobacta and mycorrhizae. This bacteria is important in forming a symbiotic relationship with host plants and are an important factor in the soil food web.  

4. Add some Tiny-Tiny Bugs:
Healthy soils provide an ideal environment for growing microorganisms. Most microorganism and plant roots are concentrated in the first couple feet of soil. Microorganisms need air, water, and food in order to thrive. Soil bacteria are the most abundant microorganism in the top soil layers. Bacteria are responsible for the breakdown of organic matter and minerals into forms which plants can use.

Mycorrhizae is a fungus which forms a symbiotic relationship with plant roots. Plant roots infected with mycorrhizae devote 15% of the plants energy to feed the fungus. In return the plant roots are better able to absorb phosphorous. Phosphorous helps fight plant diseases, promotes rapid root growth, improves water uptake to the roots, aids in blooming and fruiting, and improves nitrogen uptake from applied fertilizers.

Mycorrhizae infected plant roots are better able to absorb water making the plant more drought resistance. In addition roots are better able to absorb micronutrients such as zinc and copper. Infected roots have a longer lifespan than uninfected roots resulting in an overall increase in root density. Adding Mycorrhizae spores to the soil medium will have a huge affect on plant health and growth.

5. Make sure soil has proper aeration:
Clay soils are highly compacted limiting gas exchange between roots, microorganisms and the atmosphere. Good soil aeration allows the exchange of gasses between roots, microorganisms and the atmosphere.

As water drains from large macro-pours to micro-pours it creates a sucking vacuum which pulls atmospheric gasses from the surface into said macro-pours. This gives roots and beneficial microorganisms a reservoir of water and air to use as needed.

Roots and soil microorganisms need need the proper balance oxygen and water to thrive. As soil amendments are added it is important not to over compact the soil medium. Over compaction leads to reduced macro-pour density and thus reduced gas exchange with the atmosphere.

6. Add a layer of surface Mulch:
A top layer of mulch insulates the underlying soil and helps to moderate soil temperature. It keeps surface temperature cool on hot days and warmer on on chilly nights. As the mulch breaks down it is minerals are carried into the underlying soil, feeding the roots and microorganisms. A continuous top dressing of organic matter and mulch promotes the healthy benefits of worms castings and nematode burrowing through the amended areas. This article written by Michael Kish, President of Green Acres Nursery in Vista California. For more info visit www.GreenAcresVista.com