Remember last year when the growing season lasted until mid-October? Key to taking advantage of a long growing season is good soil.
Photo by Kurt Hildebrand.
Now that spring is approaching, many of us are looking forward to working our soil in preparation for planting our favorite ornamental plants and vegetables.
Unfortunately, some people have given up on growing a garden, thinking they just don’t have a green thumb. Others say that planting in their yard is a nightmare because their soil is too hard to work. The problem for most of us is our soil condition. It is 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 for you!
A good old-fashioned pick used in combination with a spade fork breaks up the soil without further compacting it. Working your soil when it is slightly wet will make tillage much easier and enable you to till deeper as well. A good rule of thumb is that if the soil sticks to your tool, it is still too wet to till.
Another option is the broadfork, which is an excellent choice for breaking up compacted soil and improving soil structure. Some broadforks can till to a depth of 16 inches making it an excellent tool for improving root development.
Another common tillage tool for the home gardener and mini farmer is the rototiller. The problem with the rototiller is that it may further compact the subsoil and create a plow pan that can restrict root growth and inhibit soil drainage.
A more recent 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.
If you can’t work the soil as deeply as you like the first year, it’s no big deal. It should get easier and easier each year to approach the soil depth you desire. Once you reach it (we like 2 feet for our vegetables), it shouldn’t have to be deeply tilled again for about 4 or 5 years. All that is required is light tillage to a depth of 4 to 6 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 does this have to do with plant growth? Roots, for example, need plenty of oxygen 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 can 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, it’s 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 4 to 6 inches of soil, where biological activity is high. There is no need to work it into the soil any deeper than that.
Compost or straw can also be used as mulch once plants are established. Mulch protects the soil from the impact of rain and wind, prevents soil compaction, and conserves water. Keep mulch a few inches away from your plants.
Applying organic matter is perhaps the single most important thing you can do for your soil. But, like everything else in life, balance is the key. I prefer moderate applications done two or three times during the growing season. Aim for an organic matter level of between 5 and 6 percent.
It is always a good idea to test your soil before applying fertilizers. A soil test can reveal factors that are limiting plant growth, such as excess sodium or high soil pH or other plant nutrient deficiencies.
A lab I have used in the past is Midwest Lab in Omaha, Neb. I recommend their S3C soil test package with recommendations. This package includes tests for organic matter percentage, the major and trace mineral nutrients, soil pH, soluble salts, and sodium, etc.
Cheers and pleasant gardening.
Bob Russo is a Gardnerville Ranchos resident and has a background in soil testing and analysis.
