Soil is a dynamic medium made up of minerals, organic matter, water, air and living creatures including bacteria and earthworms. It was formed and is forever changing due to five major physical factors; the parent material, time, the climate, the organisms present and the topography. ref

Soil texture

The proportions of the soil in sand, clay and silt define the soil texture type, its porosity and permeability. 1
7 à 27
28 à 50


Loamy sand
70 to 85
0 to 15
0 to 30
Sandy loam
50 to 70
15 to 20
0 to 30
Sandy clay loam
50 to 70
20 to 30
0 to 30

Soil foodweb

Trees and vegetables roots live in symbiosis with mycorrhizal fugis, beneficial bacterias and nematodes.

Mycorrhizal are specialized fungi who colonize plant roots and extend far into the soil. Mycorrhizal fungal filaments in the soil are truly extensions of root systems and are more effective in nutrient and water absorption than the roots themselves.
plant list growing mycorrhizal with bahia

Nematodes inhebit beneficial mycorrhizal fungi to develop, but can live limited in symbiosis with Brassica familly, mustards and asparagus.
Depending on the species, a nematode may be beneficial or detrimental to plant health. From agricultural and horticulture perspectives, there are two categories of nematode: predatory ones, which will kill garden pests like cutworms, and pest nematodes, like the root-knot nematode, which attack plants and those that act as vectors spreading plant viruses between crop plants. Predatory nematodes can be bred by soaking a specific recipe of leaves and other detritus in water, in a dark, cool place, and can even be purchased as an organic form of pest control.
Rotations of plants with nematode resistant species or varieties is one means of managing parasitic nematode infestations. For example, marigolds, grown over one or more seasons (the effect is cumulative), can be used to control nematodes.[30[[|]]] Another is treatment with natural antagonists such as the fungus Gliocladium roseum. Chitosan is a natural biocontrol that elicits plant defense responses to destroy parasitic cyst nematodes on roots of soybean, corn, sugar beets, potatoes and tomatoes without harming beneficial nematodes in the soil.[31[[|]]] Furthermore soil steaming is an efficient method to kill nematodes before planting crop, but indiscriminately eliminates both harmful and beneficial ones.