Soil is the most important element of any outdoor garden. The composition of the soil is the greatest determining factor of whether a plant will grow. The composition determines how the soil drains, retains water and nutrients and holds roots. Clay and sandy soils are two of the most problematic soil qualities besides rock.
Clay soil is a sticky soil. When wet, clay will stain the hands a red or orange color. Clay is shiny when rubbed by hand. When rolled between the hands, clay will form a long ribbon that does not break when wet.
Problems with Clay
Clay soil has tightly compacted pores that are difficult for air and water to penetrate. This creates problems with plants. Nutrients are not free to move throughout the soil, causing nutrient deficiencies in plants. Standing water in clay soil rots plant roots. The roots are unable to grow through clay soil that is compacted due to surface human and animal activity.
Sandy soil is gritty to the touch and will often be dry. Soils with high sand content break apart easily and will not form a clump when squeezed hard. Wet sand does not stick together. Sand particles are visible to the eye and will not merge with other grains.
Problems with Sandy Soil
Sandy soil will not hold water for extended periods. This causes drought conditions in the soil, reducing the growth of plants growing in it. Nutrients drain straight through the soil, causing deficiency. Plant roots can't take hold in excessively sandy soils.
Add organic matter to clay or sandy soils to improve their quality. A good soil is a mixture of sandy soil, clay soil and organic matter. This creates a loam soil that is dark, rich smelling and loose enough for proper drainage, air circulation and nutrient content. Organic matter such as compost, peat, wood chips or animal manure incorporated in the soil will improve its structure over time, says the University of Missouri Extension.