How to Fertilize Root Vegetables

Nitrogen is the most important nutrient for root vegetables such as carrots.

Root vegetables are fairly easy to grow, even for a novice gardener. Mostly requiring loose, deep soil and plenty of underground growing space, they are not finicky plants. However, they do require more nitrogen than other garden plants, and giving them a proper fertilization is beneficial to their health and growth. Much of the fertilizing takes place before the root vegetables are ever placed in the ground, with good soil preparation in the early spring.

Things You'll Need

• Lime
• Garden tiller or spade
• Compost
• Vegetable fertilizer

Instructions

1. Apply lime in the fall to the garden area where you will plant root vegetables. Mix 2 to 3 lbs. per 100 square feet into the soil to raise the pH level for spring planting. Do this every few years. While both lime and fertilizer enhance the soil, lime is alkaline and fertilizer is acidic. Therefore, do not add both to the garden at the same time.

2. Take a soil sample and submit it to your county extension service for an analysis of nutrient needs and pH balance. You can do this in the fall or early spring before planting. Soil sampling gives gardeners an in-depth analysis of what the soil needs to properly grow root vegetables, when to fertilize and how much fertilizer to use. For root vegetables, pH levels should be 6.0 to 6.5.

3. Till the soil deeply for root vegetables, either with a tiller or spade, and add rotted manure or compost to organically fertilize and improve the soil quality. Two or three bushels per 100 square feet is recommended. This can be done with or without any soil sample results to help produce healthy vegetable growth.

4. Prepare the soil with a nitrogen fertilizer before planting root vegetables, which can be done in addition to any composted material that was previously added. Recommendations for nitrogen during the growing season are about 1 cup of nitrogen urea for 100 square feet for carrots, rutabagas, beets and parsnips; for turnips and radishes, use only 1/2 cup. Nitrogen recommendations for beets, carrots, parsnips and rutabagas are about 3/4 to 1 cup of urea for 100 square feet. Apply half of the recommended fertilizer prior to planting the root vegetables.

5. Apply the second half of the nitrogen fertilizer to root plants in the middle of the growing season. Take care to avoid touching the leaves with the fertilizer. Instead, spread the fertilizer around the perimeter of the base of the plant. This allows it to soak into the soil but not "burn" the leaves of the plants through contact.

6. Water the soil thoroughly after application of the midseason fertilizer for optimum soil absorption, but do not leave the root vegetables standing in water.

Tips & Warnings

• You should only need to add lime to the garden soil every two to three years.

• Do not use fresh manure to fertilize plants. It can encourage root branching, which produces low-quality crops and stimulates weed growth.

References

• University of Minnesota Extension; Growing Carrots & Other Root Vegetables; Vincent A. Fritz
• Mississippi State University Extension Service; Discover Garden's Fertilizer Needs; October 2010
• University of Rhode Island Landscape Horticulture Program: Root Crops
• Vegetable Gardening Gnomes: Liming With Garden Lime -- How, When and How Much

Resources

• Arizona Cooperative Extension; Soil Sampling & Analysis; James L. Walworth; July 2006
• University of Rhode Island: Root Crops
• Ohio State University Extension; Fertilizing Vegetable Garden Soils; Marianne Riofrio
• The Dallas Morning News; Victory Gardens: Keep Soil Loose When Planting Root Crops; Rebecca Perry; February 2010