Subsoil: The term implies tilling in an out-of-sight area called the “subsoil.” Building these zones may be the most important
tillage practice, and it also may be the least understood. To understand why it is necessary to till the subsoil, we must first look under the ground into the real world of agriculture.
We will find mysterious things lying underground that can severely limit yields, regardless of how well we have managed the surface zone. Let us begin by taking a slice of the soil to see what is under there. The farmer should begin by looking for evidence of worm activity in the upper 6 to 12 inches of soil. Worms are a beautiful sight for those who understand their value. Their burrows enhance soil aeration and soil fertility. The burrow linings thrive with microbial activity. Once the soil passes through a worm’s digestive tract, the castings will be much higher in nutrients such as phosphorous and potassium than the nearby undigested soil.
We may also see a number of vertical holes that are formed by a different worm, commonly called the “night crawler.” These holes may be as large as 3/8 inch in diameter and extend from the surface to deep into the subsoil. In other areas we may not find night crawlers because while some soils may have them, others do not.