You don’t have to be a soil expert to grow great bamboo, but it certainly doesn’t hurt to have a basic understanding of how the soil may affect your bamboo. This is especially true in regions where soils are poorly suited to gardening. In this article, you will learn some basics soil characteristics and ideas on how to improve your soil.
Soil Texture and Organic Content
Soil texture refers to the proportion of sand, silt and clay in a given soil; sand particles are the largest, clay particles are microscopic and silt somewhere in the middle. A perfect loam would consist of 40 percent sand, 40 percent silt and 20 percent clay. Loamy soils are desirable because they typically have the porosity necessary for water and nutrient infiltration and drainage, (sand) as well as the capability to retain water and nutrients (silt and clay). Soil texture has to do with the mineral content of a soil, not its organic content. A quality soil will have about 45% mineral content (i.e. sand silt and clay content combined).
Organic matter consists of living and dead plants and animals, and their wastes. Organic matter is absolutely vital to soil health; it provides plant nutrients, improves water/nutrient retention and availability, aeration and drainage, just for starters. An ideal loam soil would contain about 5% organic matter, but for growing bamboo, it’s virtually impossible to overdo well-composted organic amendments. From a gardening perspective, “organic matter” likely refers to composted garden waste, manures, bark or wood chip mulches. Bark and chip mulches suppress weeds, but don’t add much in the way of nutrients that will benefit your bamboo. If you aren’t using a chemical, or bagged organic fertilizer, composted manures are excellent fertilizers. Also, many cities produce fertilizers from waste water biosolids that bamboos absolutely thrive in.
Water & Air
Water, of course, is a fundamental soil component since it is critical to plant metabolism, and is largely obtained from the soil via tiny root hairs. Most commonly associated with its role in photosynthesis, (the process of producing carbohydrates from water and carbon dioxide) water is a major component of plant tissue required for plant metabolism in general, and acts as a courier of nutrients and food to various plant organs.
Air contains nitrogen, oxygen and carbon dioxide which are all fundamental to plant metabolism. As a soil element, air is critical to plant roots for respiration, (the process of combining sugars with oxygen to create energy for growth).
Most bamboos do best in soils that contain equal proportions of air and water. With too much air (i.e. sand soil w/low organic content) the soil is unable to hold enough water and nutrients for plants to survive and thrive. With too much water, (i.e. swampy areas, or clay) air is displaced, and roots don’t get enough oxygen for respiration, which can stress or kill the plant. In a perfect loam, air and water comprise half of the soil content, 25% air and 25% water.
This term refers to the acidity of the soil, and is measured on a logarithmic scale of 0 – 14, (i.e., a pH of 5 is ten times more acid than a pH of 6) with 0 being the most acidic, 7 being neutral, and 14 the most alkaline. Soil pH affects the availability of various elements which are vital to plant growth. Nutrient availability is optimal for most plants at a pH between 6.5 – 7. Some bamboos are more suited to alkaline or acid soils than others, but most will do well in soils that range from a pH of 5.5 – 7.5. If your soil pH is beyond this range on either end of the scale, you are probably in a region notorious for the condition. Local strategies and products to implement them should be easy to find with a little research. The soil/pH relationship is very complex, as a multitude of factors affect the soil pH of a given region. Broadly speaking, regions with high rainfall tend to have soils with a lower pH (acid); arid regions tend to have soils with a higher pH (basic). Soil texture, mineral and organic content, water quality, and fertilizers also impact soil pH.
Changing the pH of Your Soil
Some common strategies for increasing soil pH include the addition of various lime products or wood ashes. The addition of manure or garden composts during bed preparation, or post-planting as a mulch can also raise soil pH. For basic soils, common strategies to lower the pH include the use of sulphur products including: elemental sulphur, aluminum and iron sulphates, and sulphuric acid. Chemical fertilizers such as ammonium sulfate or urea can also have an acidifying effect. Incorporating copious amounts of certain kinds of peat moss (pH below 5) may be more effective and environmentally friendly than a chemical approach.
Thankfully, bamboos are highly adaptable, and grow well in a variety of soils. However, west of the Cascades, regardless of the soil texture (i.e., clay, silt or sand) it’s a good bet your bamboo will benefit from additional organic matter. Composted manures and recycled biosolids are especially effective because they raise pH, improve the soil quality and provide nutrients that bamboos need to thrive. To find out more about soil management, check with your local Master Gardener, AG University, or Soil Conservation District. Books, magazines and garden shows often have recommendations for improving specific, local soil conditions as well.