The soil in a garden affects how well flowers and vegetables grow. To develop strong root systems capable of supporting the plant and providing it with water and nutrients, soil must be nutrient-rich, loose and well drained. Amending the soil with organic matter improves drainage, boosts nutrients and improves the texture of the soil. A soil test will reveal the texture of the soil and the amount of available nutrients.
Ideal garden soil is loose and friable. When squeezed into a tight ball in the hand, soil crumbles easily when touched. It does not form clods or clumps when worked and does not compact when walked on. It has a good balance of both sand and clay and is high in organic matter.
Well-balanced soil drains well. Soils too high in sand drain quickly, leaching water and nutrients away from the roots of the plant and robbing the plant of vital moisture and nutrients it requires. Soil high in clay does not allow water to travel through the soil and gets soggy. Because roots are held in water, they cannot get the oxygen they need to survive. Good soil remains moist after rains but does not become soggy or waterlogged.
Nitrogen promotes rapid growth, increases fruit production and improves the quality of the foliage. Too much nitrogen causes plants to become large and deep green but reduces the amount of blooms and fruit. Too little causes yellowed or pale leaves and stunted growth. Organic matter, such as compost or well-rotted manure, raises nitrogen levels.
Phosphorus promotes both blooming and root development. Without adequate amounts of phosphorus, plants become stunted and may exhibit purpling on the veins of leaves. Plants may appear healthy but remain small. Phosphorus levels can be raised with superphosphate or bonemeal.
Potassium helps to combat disease and improves fruit quality. Soil that lacks adequate amounts of potassium produces plants with reduced growth rates, brown edges on leaves and brown dead spots on leaves. Plants wilt easily and generally appear weak. Potassium levels can be raised by either fertilizer or organic matter.
PH is the measure of the acidity or alkalinity of soil. Measured on a scale of 1 to 14, readings above 7 are alkaline and those below 7 are acid, with a pH of 7 being neutral. Most vegetables thrive in a pH between 6.0 and 6.5. Areas with high rainfall are more susceptible to acidity and may require the addition of lime to raise the pH to an acceptable level for gardening. A simple soil test reveals the pH of the soil.