Please you have to help me?

Question

i need to know how soil composition affects the number and types of organisms an environment can support.

Answer 1

Soil is composed of sand, silt, clay, volcanic ash, and humus (including newly deposited vegetation.

The sand has a very low capacity to store and exchange with plants nutrients the plants need, but water penetrates it readily, and runs out almost as quickly if there is any drainage. So it is the weak link in supporting life.

Silt is much like sand except that its particle

es are much smaller. With much smaller particle size there is far more surface and surface tension to store plant nutrients. Silt still allows water to enter fairly readily but not nearly as easily as with sand.

Clay is so much smaller particle, but in addition it has a layered crystal structure. Its layered crystal can absorb water making the clay itself swell. This component will not absorb water readily, but will store a lot and has great ion exchange capacity to feed plants. It will hold plant nutrients fairly well, preventing it from being leached out. Clay also contains naturally the most plant nutrients.

Clay does however form a strong capillary action that pumps water to the surface as the sun shines on it, allowing the clay to bake deep and hard, and opening cracks many feet into the soil so that water can get into a drought stricken prairie field very deeply.

Clay layered crystal can be collapsed with heavy machinery, or drought, such that it becomes effectively brick, unable to absorb water to any extent for decades. This makes Clay our most fragile if most productive soil.

Humus in soil is like a sponge that holds extra water available for plant use, but it has a special value in clay soils, The humus gets into the crystals of clay, keeping them from completely collapsing. Clay with a good amount of humus recovers much faster than nearly pure clay.

Humus also delivers the plant nutrients the plants that make up the humus used to grow, but in a clay soil this is no more important than the protection from crystal collapse.

If instead of humus pyrolized  plant material is added to clay, it works even better than humus.

Gypsum and volcanic ash have a similar effect, keeping clay from collapse. They have so many different effects depending on chemical composition that one can not in general state what other effects volcanic ash will have, but often there will be metallic residues.

While sand holds water poorly, a sand with a high humus content can be among our best soils as long as the sand is moderately deep and has water pooled below.

In general, a soil that is traversed by extensive roots of previous crops will always outperform a soil that has little or none of that.

Humus of course decomposes into either CO2 or methane, so it is under attack by some environmentalists, even to the extent that the Green Party of Canada proposes to tax farmers for the humus content of their soil (or at least the expected amount of CO2 it will release.