Nitrogen is one of the most important nutrients for vegetable production, but it can also be one of the easiest to lose (by leaching), especially on New Jersey’s sandy Coastal Plain soils. Heavy rainfall or excessive irrigation can move nitrogen below the crop root zone before plants have a chance to use it.

One way growers can improve nitrogen-use efficiency is through fertigation. Fertigation is the application of fertilizer through an irrigation system. In many New Jersey vegetable crops, including tomatoes, peppers, cucumbers, pumpkins, watermelons, and sweet corn, drip irrigation systems can be used to deliver small amounts of nitrogen throughout the season rather than applying all of it at planting.

Applying nitrogen in smaller, timely doses helps match crop demand and can reduce the risk of nutrient losses. Fertigation also gives growers more flexibility to adjust nitrogen programs based on crop growth and weather conditions. For example, following periods of heavy rainfall, growers can evaluate fields and make adjustments if additional nitrogen is needed.

Like any management practice, successful fertigation depends on proper irrigation scheduling. Applying too much water can still move nutrients below the root zone. However, when irrigation and fertilizer applications are properly managed, fertigation can be an effective tool to improve nitrogen efficiency, support crop productivity, and reduce nutrient losses.

When does fertigation make sense?

• Fields equipped with drip irrigation systems.
• High-value vegetable crops with season-long nutrient demand.
• Sandy soils with greater leaching potential.
• Situations where growers want flexibility to adjust nitrogen applications during the growing season

Common New Jersey crops where fertigation may be beneficial

Tomato, pepper, cucumber, pumpkin, watermelon, muskmelon, and sweet corn production systems that utilize irrigation.

Some common things to know when fertigating

• Use only fully soluble fertilizers that can move easily through the irrigation system.
• Base fertilizer selections on soil test results. Fields with high phosphorus (P) and potassium (K) levels may only require supplemental nitrogen during the season.
• Common fertigation materials include soluble NPK fertilizers, calcium nitrate, and potassium nitrate.
• Ensure fertilizer injectors are properly calibrated and matched to the flow rate of the irrigation system for uniform nutrient distribution.
• Start irrigation first and allow the system to reach normal operating pressure before injecting fertilizer.
• After fertigating, continue irrigating briefly to flush fertilizer from the drip lines.
• Avoid over-irrigation, as excess water can move nutrients below the root zone and reduce fertilizer-use efficiency.
• Regularly inspect drip lines, filters, and injectors to ensure the system is operating properly.
• Calculate fertigation rates based on the actively cropped area rather than the entire field acreage.

References

• Ernst, T., McWhirt, A., Zimmerman, T., Henderson, E., Duncan, M., and Lay-Walters, A. Basics of Drip Irrigation and Fertigation for Specialty Crops (FSA6160). University of Arkansas Cooperative Extension Service.
• Johnson, G. 2010. Fertigating Drip Irrigated Vegetables. University of Delaware Cooperative Extension, Weekly Crop Update.
• Kelley, L. 2026. Nitrogen Prices Spawn Interest in Fertigation. Michigan State University Extension.