In the next few posts, we will share a report from the Master Gardener Program notes 711, CSU Extension, covering the topics of soil management and fertilization for your vegetable garden.
In the garden, managing soils to improve tilth and garden fertilization are related but not necessarily the same process. For example, compost or manure may be added as a soil amendment to improve tilth; however, they will add nominal amount of plant nutrients. A manufactured fertilizer may be added to supplement soil fertility levels, but it will not improve a soil’s tilth. For optimum yields and quality, gardeners need to pay attention to both soil management for improving tilth and soil fertilization.
Tilth is a term related to the suitability of a soil to support plant growth. Technically speaking, tilth is “the physical condition of soil as related to its ease of tillage, fitness of seedbed, and impedance to seeding emergence and root penetration”.
Soil Amendment or Fertilizer
The term soil amendment refers to any material mixed into a soil. By law, soil amendments make no legal claims about nutrient content or other helpful (or harmful) properties. Compost and manure are common soil amendments used to improve soil tilth. They may also supply nominal amounts of plant nutrients. Some of the nutrient effect seen from adding soil amendments is likely due to their effect on soil microorganisms. The organic material in soil amendments is a food source that allows microorganisms to multiply. The larger numbers increase the conversion of nutrients already in the soil to plant usable forms.
Mulch refers to a material placed on the soil surface. By law, the term fertilizer refers to a material that guarantees a minimum percentage of nutrients (at least the minimum percentage of nitrogen, phosphate, and potash). An organic fertilizer is derived from natural sources and guarantees the minimum percentages of nitrogen, phosphate, and potash.