How does pH affect soil fertility and how is this related to plant growth?

Soil is an important resource that can take hundreds of years to form. Plants rely on soil to obtain nutrients along with water and gases. The pH of soil ranges between 4 and 8 and an optimum soil pH is somewhere between 6 and 7 for plants to be able to grow. Different pH values can affect properties of soil including the rate that certain nutrients leach out of the soil. The reason for this is that certain nutrients are more or less soluble at different pH values.

To maintain the fertility of soil, the process of decomposition, carried out by bacteria and fungi returns organic and inorganic materials back to the soil. The use of fertilizers can increase soil fertility as well. Methods used by farmers to increase fertility include--contour plowing, strip cropping, terracing and crop rotation which all helps to decrease erosion while at the same time preserve soil fertility. Conservation tillage leaves remnants of the previous year's crops on the field helps to maintain fertility, decrease erosion and holds water in the soil. If a soil contains particles of clay which have a negative charge, these will attract positively charged particles of calcium, magnesium, ammonia among others which helps to maintain soil fertility. Clay soils can hold nutrients very well and loam which is a mixture of sand, silt and clay particles also can hold nutrients in place.

Soils can be divided into types known as Orders and these differ based on the area in which they have formed and from what materials are found in these soils. Some of the 12 Orders include: spodosols, mollisols, aridosols, oxisols and alfisols. A spodosol is not great to use for farmland because of the acidic pH due to a leaf litter composed of coniferous trees' needles which are acidic when they break down. The nutrients leach through the soil therefore, it has poor fertility. To contrast, an alfisol which forms in temperate deciduous forests has high soil fertility which is maintained by the leaf litter because trees in these temperate areas lose their leaves each fall and then decompose adding nutrients back to the soil.

Soil fertility is in a delicate balance and must be maintained by natural processes along with the prudent use of conservation practices and fertilizers so that this important resource is available for future use.