Topsoil is the top layer of dirt that helps to sustain all life. Organic matter decomposes and combines with the top layer of soil, providing nutrients to plant life, which in turn will grow, die and become more organic matter for the soil. This is a constantly recycling form of fuel for the earth. The earth's natural process takes 500 years to make 1 inch of top soil, according to the University of New Hampshire. Great topsoil is described as rich, dark and loamy, but it can take more than just looking at it to know if it really is great soil.
Sand in Great Topsoil
Great topsoil needs sand, but it should contain less than 52 percent of it. Topsoil should be free of debris and rocks and have a fine texture. Sand gives the soil an airy consistency so that water drains from it freely. Adequate drainage is vital to a healthy plant as water helps to cleanse the earth of bacteria and diseases that can grow in standing water.
Silt in Great Topsoil
Silt in topsoil is the organic matter that is so vital for supplying nutrients to plants. Silt is decomposed plant and animal matter that has fallen and degenerate. Compost is added to soil to elevate the soil's silt content and to add necessary nutrients. For growing a garden, the soil should be about 25 percent silt or organic materials. Silt also helps plants to retain water and to circulate oxygen through the soil. Silt is a soft material that cannot be tightly compressed.
Clay in Great Topsoil
Clay should be between 7 and 27 percent of a soil mixture. It helps to retain moisture and provide stability for plants to hold onto in the ground. Roots can cling to clay and keep it from toppling over. Too much clay, however, makes a soil retain water and restricts the flow of oxygen.
The pH Factor in Topsoil
For optimal garden production and health, the pH of garden soil should be between 5.5 and 7.5. Local cooperative extensions can test soil, and many nurseries and garden centers have easy-to-use kits. The pH is a measurement of the relative acidity of the soil. This lets the gardener know if lime or fertilizer needs to be added to the soil to create the best possible growing environment.