Healthy plants develop by taking in nutrients through the roots. Roots can only absorb nutrients that are dissolved, so solid soil components and compost need to be broken down through the action of soil micro-organisms. Thousands of fungi and soil bacteria naturally exist in fertile soil, but worm castings are also a great source of soil bacteria. Nitrogen, phosphorus, potassium & calcium are the major plant foods, but plants also require other trace elements. All these as well as water are absorbed through roots.
Absorption of nutrients through roots is an active process. Roots actively do work, so like you and me, they need oxygen. Soils need to have a sponge-like texture in order to deliver both water and oxygen.
- Clay soils hold water but can be anoxic.
- Sandy soils are well aerated but do not hold water.
- Organic soils rich in compost can hold water and supply air as well.