Spring Soil Improvement Tips
Now that spring is just around the corner, many of us look forward to working our soil in preparation for planting our favorite flowers
and vegetables. Unfortunately, some of us have given up on trying to grow a garden, thinking we just don’t have a green thumb. Others, especially new homeowners, say that planting a garden is a nightmare because the soil is “like concrete”. The problem for most of us is our soil condition. It’s true, we can’t do much to change the type of soil we have on our property, but we can significantly improve it. So, what can we do?
The first step toward improving the condition of a highly compacted soil is deep tillage. Our goal is to develop a “granular” soil structure, which is the most favorable for adequate gas exchange. If the soil remains compacted or crusted, plant roots will remain undersized and certain forms of soil life (aerobic microorganisms, earthworms, etc.) will not adequately flourish. A deep and well-developed root system is better able to extract water and nutrients from the soil, which means less watering and fertilizing are needed.
A good old-fashioned pick, used in combination with a spade fork, breaks up the soil without further compacting it. Working soil when it is slightly wet will make tillage much easier and enable us to till deeper as well. A good rule of thumb is that if the soil sticks to our tool, it is still too wet to till. Another excellent choice for reducing soil compaction and improving structure is the broadfork. Some broadforks can till to a depth of 16 inches making it an excellent tool for improving root development.
An additional tillage tool commonly used by the home gardener and mini-farmer is the rototiller. A rototiller, however, may further compact the subsoil and create a plow pan that can restrict root growth and inhibit soil drainage. A more favorable option for the mini-farmer is the use of a spader, which breaks up the soil without compacting or inverting it. It can also be used to prepare the seed bed for transplants or direct seeding.
Working the soil as deeply as we’d like the first year can certainly be a challenge on tight and compacted soils. But, there is no need to despair! Approaching the desired soil depth is likely to get easier each year. Once attained, (we like two feet for our vegetables), it shouldn’t have to be deeply tilled again for about four or five years. All that is required is light tillage to a depth of four to six inches in the spring or fall prior to planting.
Why deep tillage? It promotes good soil drainage and an ample supply of soil air, both of which are a must for optimum plant growth. Simply put, a gas will always spread out or diffuse from an area of high concentration into an area of lower concentration. The quantity of carbon dioxide is typically higher in the soil than in the atmosphere and vice versa for oxygen. Consequently, each gas will disperse in the direction of lower concentration to seek equilibrium.
So what’s this have to do with plant growth? Roots, for example, need plenty of oxygen in order to take up plant nutrients and water. As oxygen is consumed, large amounts of carbon dioxide are given off. Soil life, which plays a major role in the conversion of organic matter into plant-available nutrients, also consumes oxygen and releases carbon dioxide. Gas diffusion ensures the replacement of oxygen consumed in the soil. It also allows the high concentration of carbon dioxide in the soil to spread out into the air where plant leaves are able to capture and use it in the process of photosynthesis. This is nature’s way of recycling carbon back into the plant, which is ultimately converted into sugar (plant’s energy source) in the presence of sunlight.
Organic materials, such as compost and leaf mold, are especially beneficial for improving soil structure, water retention, and nutrient availability. Plus, they are a valuable energy source for soil organisms. Compost can be spread on the soil surface after deep tillage is completed and then lightly worked into the top two to four inches of soil.
Applying organic matter to the soil is perhaps the single most important thing to do. But like everything else in life, balance is the key. Once the soil building process is completed, moderate compost applications once or twice a year, are often all that are needed. An organic matter level of between five and six percent would be ideal.
Cheers and pleasant gardening!