Good soils are deep, but covered with a rich layer of decaying organic matter, and simultaneously moist, but capable of draining quickly. Soil should also consist of fine grains, but have plenty of structure, which allows large air spaces to form in the soil. These air pockets are vital for allowing the roots of plants and trees to obtain the oxygen they need.
Rather than being a collection of dead, mineral-based material, good soil has an entire community of microorganisms living inside, recycling the nutrients present in the organic matter. The fresher the soil is, the better, as soils that have been fertilized heavily or have already been used to grow several generations of crops are likely to be rather sterile. It will take some time and the addition of considerable amounts of organic matter to replenish the microbial community and proper nutrient balance in the soil.
The United States, Canada and many other countries at temperate latitudes have excellent soil. Some places, such as New Zealand, have very little land area with high quality soil. In such places, the local citizens and governments must decide what types of activities, such as agriculture or residential development, should take place on high-quality soils.