Soil acidity (and acidity of anything else, for that matter) is measured on a scale of 1 to 14. Everything below 7 is considered to be acidic. Everything above is considered to be alkaline. Most garden plants thrive at a pH between 6 and 7.5. The reason a pH between 6 and 7.5 is optimal for garden plants is that between 6 and 7.5, phosphorus in the soil is soluble - meaning that it dissolves in water and is taken up by plant roots.
Some of the factors that affect the rate at which particles diffuse include: the particle's molecular weight, temperature, concentration difference, diffusion distance, permeability and surface area. Pressure is also known to affect the rate of diffusion since it increases the speed of molecules.
Limiting factors determine the immigration capacity of a population. 2. A limiting factor controls the growth of a population. 3. Limiting factors operate when growth is exponential. 4. Populations grow too large in the absence of limiting factors. 5. Competition is an example of a limiting factor. 6. Population size can be limited by factors such as predation.