Managing fertilizer costs can be the difference in profit and loss in any crop. The high cost of all fertilizers, especially nitrogen, is a critical production expense for all farmers, but can be especially important to high value, high input vegetable crops.

Several factors have combined to create the upward spiral in the cost of nitrogen and other crop nutrients. Ammonia is a common component of most fertilizers. It takes 32 million cubic feet of natural gas to produce one ton of ammonia.

Only three percent of natural gas supplies is used to produce ammonia, so the fertilizer industry has virtually no impact on the price of natural gas, according to Roger Teal, public service assistant and horticulturist at the University of Georgia.

The price of anhydrous ammonia has increased from 12 cents to 31 cents per ton of nitrogen. Among the more popular forms of nitrogen, ammonium nitrate has increased from 26 to 45 cents per ton of nitrogen and urea from 22 to 39 cents per ton. Ammonia is a common component of these and other forms of nitrogen fertilizer.

Ammonia production in the U.S. has dropped more than 25 percent in the past 12-15 years, despite a worldwide increase in demand of 13 percent over the past five years. Worldwide nitrogen use is up 10 percent, phosphorus use is up 13 percent and potash use is up 25 percent in the past five years.

In cereal grain production during 2005, it is estimated 3.3 billion tons was applied in corn. It is well documented that corn only uses about 33 percent of the nitrogen applied. Based on total nitrogen use, U.S. corn farmers lost $2.6 billion in material lost to the atmosphere.

Considering most vegetable crops require higher rates of nitrogen than corn, it is reasonable to assume the cost per acre lost to the atmosphere is higher in vegetable crops.

The combination of higher production cost, lower domestic production, and increased world demand has placed U.S. farmers in a bad situation. The solution, Teal contends, is based on three basic principles:

  • Use the proper application equipment and be sure that it is calibrated accurately.

  • Use the best source of nitrogen, not the traditional or favorite source.

  • Use the correct rate, not the broadcast rate that covers all soil conditions.

“You cannot see over-use of nitrogen. It is easy to look at a field and know when too little is used, but too much is a different story,” Teal says. Knowing exactly how much nitrogen and other fertilizer is needed by the crop and applying them in the right amounts and at the right time can be the difference in profit and loss in vegetable production.

Nitrogen (N) is an important element for economic vegetable production, and is especially required for successful production on sandy Southeastern soils characteristic of the Coastal Plain. Sandy soils typically have low organic matter and retain little nitrogen against leaching.

Intense rainfall, or excessive irrigation water, can leach nitrogen from the root zone and potentially into groundwater. Nitrogen management strategies should be used on vegetable farms to maximize the chances that nitrogen fertilizer will benefit crop yields and fruit quality, while minimizing the chances it will be lost to the environment.

Water management is another critical component of nitrogen management on vegetable farms in the Southeast. Regardless of the form or source of nitrogen fertilizer, the end-product, in a few days to a few weeks, is the nitrate ion, which easily leaches in sandy soils.

Several production practices can help vegetable growers incorporate good water management into good nitrogen management strategies. These include:

  • Using polyethylene mulch where practical, and applying nitrogen in the root zone under the mulch.

  • Scheduling nitrogen applications to coincide with crop need and avoiding large applications at any given time, part of which might be leached before being utilized by the crop.

  • Avoiding the application of fertilizer or nitrogen-containing organic materials, such as sludge or manure, to farm roads, field alleys, row middles or other areas not planted to vegetables.

  • Avoid over-use of nitrogen fertilizers to minimize the chances of large residues being left in the field at seasons end.

One application technique is pre-plant banding to improve efficiency. Though banding has been used for many years to apply phophorus and potash, Teal says recent studies indicate banding nitrogen on some crops may be the most efficient way to maximize plant utilization and reduce total usage.

In some crops foliar application has proven the most efficient. Teal says not enough information is available to recommend foliar application of nitrogen on vegetables, but it is one area of research he will be investigating. Regardless of the crop or the fertilizer used, surface broadcast is the least efficient, Teal adds.

In tests on bell peppers at two sites in south Georgia in 2006, Teals says there was little variation in yield from any of four sources (two ammonia and two nitrate) of nitrogen when used at comparable rates.

He points out that the cost of nitrogen by source is different. If the more expensive forms are used in pepper production, some growers are paying too much for nitrogen.

A critical factor for vegetable growers to consider is that nitrogen response fluctuates, and it fluctuates separately from yield. The soil gets nitrogen from rainfall and other natural sources, so a critical measure of how much nitrogen to use is based on what is available in the field before the crop is planted.

High tech equipment, like chlorophyll sensors, can be used to determine precise rates of nitrogen needed and used by a crop. Likewise, low tech practices, like planting test strips based on yield potential of a crop, can be used. Regardless of how a grower determines rate, form and application method, getting it right will save huge amounts of money in vegetable production.