Vegetables and Ornamental Horticulture : Preventing Fertilizer Injury

PREVENT FERTILIZER INJURY THIS SPRING

Steve Reiners
Associate Professor in Horticultural Sciences at Cornell University

This spring's dry conditions have been excellent for planting but growers need to take special care when it comes to banding their fertilizer. All nitrogen and potassium fertilizers add soluble salts to the soil. These salts are capable of burning tender roots of germinating seeds. Crops that are especially sensitive include snap and dry beans, carrots and onions, while corn, cabbage and lettuce are moderately sensitive.

Fertilizer injury occurs most often in dry springs and when fertilizer bands are placed too close to the seed. To prevent injury, keep the amount of N + K20 below 80 to 100 pounds per acre in the band. Phosphorus will not cause burning and does not figure into the equation. Make sure the band is placed 2 inches below and two inches to the side of the seed furrow. If you need a higher rate in the band, move the band further from the furrow. Also, using liquid fertilizer is just as hazardous as dry fertilizer. Many growers incorrectly assume that liquid starter is safer do to the extra water applied. But the amount of water actually added on a per acre basis is miniscule, far below the amount of water necessary to prevent salt injury.

In addition to salt injury, materials containing nitrogen may produce an injury due to a high concentration of ammonia. These include fertilizers containing urea, diammonium phosphate (DAP), or anhydrous ammonia. Exceeding 30 pounds of N as urea or DAP (either in combination or alone) in bands at planting may cause seedling injury. If anhydrous ammonia will be used preplant or as a preemergence source of N for sweet corn, it should be injected as far as possible from the seed.

If you realize there was a problem after planting, irrigating as soon as possible is recommended. The water will dilute the fertilizer salt and leach some of it away from the seed.