The Art of Soil Building and Soil Fertility

Written by David S.

What is the art of building soil? For anyone who grows plants the art of building soil is the process by which we improve soil quality so that whatever it is that we grow can thrive. Soil fertility and soil improvements are two of the factors by which we measure how well we are doing at building soil. Soil fertility is the percentage of soil nutrients that are available to plants within the soil – in-ground or container planting. Soil improvement is the plan we undergo to raise the amount of nutrients in the soil. In the case of containers, the process becomes critically important as containers are considered an artificial growing environment. In-ground plants – trees, flowers, shrubs, etc., are also dependent upon the quality of the soil. 

Building Soil and Amendments 

The easiest way to build quality soil is to amend the soil with material that adds nutrients, minerals, and airflow to the soil. All three of those factors contribute to a plant’s ability to grow and thrive. When we fail at building quality soil, plants struggle to grow, and they are often discolored, stunted, and in the case of flowering plants, produce small blooms that are sparse.

Soil Amendments 

Soil amendments include:

• Fertilizers – organic and manufactured – dry or liquid – time release, water-soluble, plant-ready, etc. 
• Compost – bagged or freshly gathered from your yard or via meal preparation
• Cover Crops – Planted plants or crops that help to fix soil nutrients or change the chemicals found in soil into usable plant nutrients. 
• Aggregates – perlite, vermiculite, lava rock, gravel, and material that changes the way soil drains 
• Moisture Retainers – coconut coir, perlite, vermiculite, organic matter, etc. 
• Manure – aged or raw

These are a few examples of broad categories of soil amendments They are useful for improving the relationship between what you plant and the soil into which you plant your plants. Some address soil nutrition. Others help to improve the growing environments by improving the quality of the soil. 

Soil Quality as a Physical 

The physical quality or characteristics of your soil is important. We are talking about topics such as heavy clay soils, sandy soils, loams, and even topsoil. Soil quality goes beyond nutrition and addresses the physical needs of plants. Some plants, such as periwinkle, do quite well in soil that has low nutrient levels and is sandy. Most garden vegetables need rich, loamy soil that drains well. Marginal plants, those plants that grow along flood zones or near lakes, often need soil that is poorly draining. 

When you address the physical needs of soil you are mostly talking about two factors – airflow and water drainage. 

1. Airflow – soil with good airflow allows air to circulate around the plant roots. The air helps to prevent anaerobic bacteria, which causes the soil to smell like a sewer. Anaerobic – “an” means without and “aerobic” mean oxygen, so anaerobic soil has little air movement. When you do aerobic exercise you take in more oxygen. Soil needs to breathe as the exchange of oxygen helps to bring airborne chemicals – oxygen and nitrogen into the soil. Soil with poor nutrient levels is generally heavy and that denseness prevents the exchange of air. An example of soil that is heavy and lacks air movement is peat from peat bogs. 
2. Water Drainage – Soil either holds water, causes water to pool, or allows water to seep through. Heavy clay soils tend to cause water to absorb into the soil or for the water to pool. Sandy soil allows water to drain away quickly and likely will not have much material that absorbs water. Loam is light and airy and water absorbs into some material within the loam and the rest drains away. 

Water drainage and soil airflow are managed by decreasing or increasing the amount of aggregates in the soil. Sandy soil is improved by adding organic matter, such as compost, manure, and other aggregates, such as wood chips, perlite, or vermiculite. Heavy clay soil is improved by adding sand or aggregates to the clay. The presence of sand helps water to drain. 

Soil Quality by Nutrient level

Building better soil nutrient levels is all about adding amendments or using cover crops. Plants use a variety of nutrients including nitrogen, phosphorus, and potassium. They also use minerals such as zinc. Soil nutrient levels pair with the physical qualities of soil to produce a growing environment that favors healthy plant growth, an abundance of flowering and fruiting, and the curation of healthy, strong, and vigorous root systems. Soil nutrients also drive plant processes such as flower and bud development, fruit set, and photosynthesis. 

With humans, we are what we eat. If we want to have strong, healthy bodies with few illnesses and plenty of energy, we eat healthy foods and drink plenty of water. With plants, it is the same. For a plant to fully function it needs healthy soil, air exchange at the soil level, and plenty of water. 

You can address poor soil nutrient levels by:

• Having your soil tested for nutrients, etc. 
• Addressing the deficits in the results of your soil test
• Adding mulch to help the soil retain moisture
• Amending with fertilizers – in-soil products that you dig into the ground or water-soluble fertilizers that you apply with a hose or foliar sprayer, or time-release products that dissolve slowly on top of the soil. 
• Planting cover crops while the ground is fallow. 

Cover Crops vs. Fertilizers and Amendments

Cover crops help you build healthy soil that is more sustainable in terms of soil health and longevity. Fertilizers are a faster approach to addressing plant nutrient needs, and they are handy when you have a plant or crop that has a narrow band of nutrient requirements. 

Cover crops need time to do their job – usually a season but sometimes longer. If the soil nutrient load is very low, it can take years for cover crops to regenerate the soil nutrient levels. While they are timely, you end up with better soil health – soil that is loamier, drains well and is full of beneficial biota. 

Cover crops are generally in the pea or legume family of plants. They include:

• Clovers
• peas
• beans
• Soybeans
• Alfalfa 

For the home gardener or those who have smaller farms, such as market gardeners, inter-planting cover crops with compatible crops are one way to utilize the benefits of cover crops without having to wait for years for those crops to do their job. Cover crops also work well when you have only one seasonal garden per year, such as a summer garden. You can remove the summer garden at the end of the season and replant the area with cover crop plants. When it is time to resume gardening the following growing season, the soil will regenerate its nutrient levels. 

Inter-planting is mixing plant types – tomatoes planted next to basil, lettuce planted next to cucumbers – these mixed plantings allow you to use the growing space more efficiently. When you plant beans and corn, the beans help to fix nitrogen in the soil and the corn helps to support the beans. 

Do you need to use cover crops? 

Do you need to use cover crops? No, you do not. Commercial farmers rarely use cover crops. Instead, they rely on inputs, such as fertilizer or nitrogen to produce a growing environment for their crops. 

How do cover crops work with or replace fertilizer What is inter-planting? Does it help build soil health? Soil amendments to keep on hand. Relying solely on fertilizers to regenerate soil nutrient levels leads to some problems. The soil structure deteriorates, and you can lose soil depth due to wind and water erosion. Eventually, you also lose the beneficial soil biota and then have to counter with pesticide or herbicide usage to prevent or control crop damage. The process of regeneration following commercial farming can require years of soil maintenance, cover crops, and costly inputs to bring soil health back to a sustainable level. 

Soil Amendments To Keep On Hand 

There is not a perfect list of soil amendments that you should keep handy. If you are growing specific types of plants – roses or hydrangea, then you will keep soil amendments on hand that support those crops. It is always a good idea to have access to:

• Compost tea – you dissolve it in water and then water your plants with the product. It provides instant nutrients to plants and some teas may also contain beneficial soil biota. 
• Organic nitrogen – look for products that are 5-0-0 or 10-0-0 – these help green-up plants and provide them with the nitrogen to produce green leaves and healthy stalks.
• A balanced fertilizer in the 5-5-5 or 10-10-10 range. You will use these when you transplant or when you till up your garden area. 
• Mulch – bagged mulch will help new transplants undergo the transplanting process easier, keep soil moisture levels in place, and keep the soil from drying out on hot days. 
• Topical fertilizers such as manure or compost that you apply around plants. These can also act as a mulch for a short while, but they also replace the humus layer of the soil and will help to increase the thickness of growing space within the soil. 

Explore all the soil building options by visiting any of our five Southern California locations. Green Thumb Nursery offers an exceptional range of fertilizers, soil products, and tools to make the process of creating or maintaining healthy soil easier. 

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