Vegetable Gardening Tips for Adding Fertilizer and Lime to Soil

The pH level and nutrients both affect the way a plant can grow.

All vegetables take up nutrients from the soil. These nutrients help the plant to grow larger and produce larger vegetables. A plant's ability to absorb nutrients is a function of the soil's pH. Prior to planting vegetables, many gardeners and farmers add lime and fertilizer to improve the soil's pH and nutrient content.

Soil pH

All plants have a pH range in which they grow best. Plants such as azalea and blueberries grow well in an acidic pH range below 7.0. Most vegetables grow in a neutral pH range around 7.5. Plants that grow within soil that meets their pH requirement can access nutrients found within the soil. But if a plant is grown in a pH that is not right for them, the plant is unable to absorb the nutrients in the soil. Symptoms of poor pH may include yellowing of the leaves caused by iron chlorosis, a condition that occurs when plants are not able to absorb iron.

Lime

Lime is actually dolomite limestone, a crushed form of limestone that is alkaline in nature. Adding lime to soil helps to raise the pH level of soil. Not all soil needs lime. Soil that is already very alkaline in nature such as soil that has had too much lime added in the past or is in an area where limestone formations already add lime to the soil may need sulfur to lower the pH level down from above 7.0.

Fertilizer

Fertilizer usually is labeled with three numbers. Each number represents the content of one of three major nutrients in the fertilizer: nitrogen, phosphorous and potassium. Soil typically needs only a certain amount of each nutrient. When too much of a nutrient such as nitrogen is added, the excess fertilizer can burn crops and be carried off with rainwater and cause pollution in bodies of water.

Soil Test

Prior to adding fertilizer and lime to soil, gardeners should conduct a soil test. This test indicates the soil's pH and the nutrient content of the soil. Knowing these factors can help a gardener adjust amendment amounts for the soil. A good time to conduct a soil test is in fall prior to planting. Most soil laboratories do not receive as many soil tests in fall as they do in spring, so the person submitting the soil test should receive the test results sooner. Soil amendments should be added to the soil six weeks prior to planting to allow the fertilizer and lime to change the soil's pH and structure.

References

• Utah State University Extension; What Is Iron Chlorosis and What Causes It?; Michael Kuhns, et al.; January 2003
• Colorado State University Extension; Choosing a Soil Amendment: J.G. Davis, et al.; May 2005
• University of Minnesota Extension; Soil Test Interpretations; Carl J. Rosen, et al.; 2008

Resources

• Washington State University Extension; The Myth of Soil Amendments Part II; Linda Chalker-Scott
• University of Florida IFAS Extension; Producing Garden Vegetables; J.M. Stephens, et al.
• Rutgers University Extension: Soil Testing Laboratory