Compost delivers nitrogen to soil
How Compost Delivers Nitrogen to the Soil...
Read this first to help understand the information below: the microbial community in the soil (micro-organisms, bacteria, fungi and assorted small critters and insects are the primary feeders on the compost. It is the chemicals they produce in their waste or their decomposing bodies that lay down the chemicals in the soil that the tips of plant roots will feed on.
It is important to "feed" this top 6 inches of the soil for two reasons: this area, the rhizosphere, is where most of the decomposers live and it is generally regarded as the 'root area' of the soil.
If you think of 1,000 square feet as an area roughly 30 feet square, it will be easier to guage how much compost you need.
Although this says to add compost in the fall, new gardens (ideally) should be composted in the fall and again in the spring. Many gardeners add ccompost both in the spring and the fall. DO NOT TILLTHE COMPOST INTO THE SOIL. Tilling destroys the structure of the soil and is a huge impediment to the good work of the crucial creatures in the soil. Invest in an earth fork (a glorious tool!) and simply turn that soil over.
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Because it is the microbial community (bacteria, fungi, microscopic creatures) in soil that provides nutrients for plant growth, it is important to "feed" the soil only what the microbes can utilize efficiently and productively. Plants break down the nitrogen in the compost slowly and steadily as the health of the soil generally improves.
As an example, if a homeowner added the recommended rate of one inch of compost per square foot over 1,000 square feet ( roughly 31 feet by 31 feet) this would be approximately one ton of compost and it would deliver about 20 pounds of nitrogen to the soil. However, not all the 20 pounds of nitrogen is available to the plants because they need to break it down to ammonium or nitrate nitrogen, which is the only form of nitrogen plants can consume.
The first year 10% (or two pounds) of the nitrogen in this ton of compost is available to the plants.
The second year 3-5% or approximately one pound (of the original 20)is available to the plants.
In the third year only 1-3% or approximately one pound (of the original 20) is available to the plants.
Therefore, when a gardener applies city compost at the rate of one ton (or one inch per 1,000 square feet) which is what most plants need to thrive and produce vegetables and flowers abundantly.
Our area soils in western South Dakota are generally understood to have between 1.5 and 3% organic matter. Yearly applications of approximately one inch of compost incorporated approximately 6-8 deep (the root layer of the soil) in the fall will steadily improve the percentage or organic matter in the soil.
You will see the health of the soil, the vigor of the plants, the improved ability of the soil to hold moisture and the reduced need for additional fertilizer and/or pesticide/herbicide use.
The fine screened (3/8") compost can also be used as a 1/2 to 1" top dressing on flower and vegetable gardens.