How Much Nitrogen Does Corn Need?

Corn typically needs 180-250 pounds of nitrogen per acre, or about 1 pound per bushel of expected yield. Your exact rate depends on yield goals, soil organic matter, previous crops, and recent manure applications.

Below, you will learn:

• What factors determine nitrogen rates
• When to apply nitrogen for maximum efficiency
• Which nitrogen sources work best for your operation
• How soil type affects nitrogen management
• How to test if your corn needs more nitrogen
• What happens when corn gets too much or too little nitrogen

What Factors Determine How Much Nitrogen Your Corn Needs?

Your corn’s nitrogen needs depend primarily on your yield goal, with most fields requiring about 1 pound of nitrogen per bushel of expected yield. So, if you’re targeting 180 bushels per acre, you’ll need roughly 180 pounds of nitrogen.

But that’s just the starting point.

Your soil’s organic matter provides free nitrogen every year. For every percent of organic matter, you can subtract 20-40 pounds from your total nitrogen needs. A field with 3% organic matter might naturally contribute 60-120 pounds of nitrogen.

Previous crops make a big difference too. Soybeans fix nitrogen in the soil, letting you reduce applications by 30-40 pounds per acre. Corn following corn needs the full rate since the previous crop used most available nitrogen.

If you’ve applied manure recently, you’ll need to account for that nitrogen credit. Fresh dairy manure might provide 50-100 pounds of available nitrogen per acre in the first year. Composted manure releases nitrogen more slowly but lasts longer.

Here’s a simple calculation for a 200-bushel yield goal on a field with 2% organic matter following soybeans: 

Your local extension office can provide more precise recommendations based on your region’s soil tests and climate patterns.

When Should You Apply Nitrogen to Corn?

The best nitrogen timing depends on your equipment and weather, but split applications typically give the highest yields and efficiency. Most operations apply 30-50% pre-plant and the rest at sidedress.

Pre-plant nitrogen gets your corn started strong. Apply it within two weeks of planting to minimize losses, especially on sandy soils that lose nitrogen quickly to leaching.

Sidedress applications at V6-V8 stage (knee-high corn) deliver nitrogen when corn needs it most. This is when corn shifts into rapid growth mode and nitrogen uptake accelerates dramatically. A 200-bushel corn crop takes up about 55% of its nitrogen between V6 and silking.

Weather changes everything though.

Wet springs can wash away nitrogen applied in fall or delay sidedress applications. If you can’t get into wet fields for sidedressing, having that pre-plant nitrogen becomes your insurance policy. Dry conditions slow nitrogen conversion in soil but also reduce losses.

Some growers are moving to three-way splits: starter fertilizer, pre-plant, and sidedress. This approach reduces risk and can boost yields by 5-10 bushels per acre. The downside is more trips across the field and higher application costs.

For anhydrous ammonia, fall application only works in northern areas where soil temperatures stay below 50°F. Southern operations should stick to spring applications to avoid nitrogen losses over winter.

What Forms of Nitrogen Work Best for Corn?

All nitrogen sources work for corn, but your best option depends on equipment availability, application timing, and cost per pound of actual nitrogen. Here are your main options:

• Anhydrous ammonia (82% nitrogen): the most concentrated and usually cheapest per pound, but requires very expensive specialized pressure tanks and injection equipment, so most farmers hire custom applicators.
• UAN solutions (28-32% nitrogen): liquid fertilizer you can spray, inject, or dribble between rows for sidedressing without damaging corn roots, offering the most application flexibility.
• Dry urea (46% nitrogen): spreads easily with standard equipment but needs rain or tillage within 48 hours to prevent losses.
• Protected nitrogen products: polymer-coated or stabilized forms that cost 10-30% more but reduce losses in wet conditions.

Your nitrogen dealer can help calculate the true cost per pound of nitrogen including application costs. Sometimes the “expensive” option delivers better returns when you factor in labor, equipment, and potential yield gains.

How Does Soil Type Affect Corn’s Nitrogen Needs?

Your soil type determines how much nitrogen you’ll lose to leaching or gas emissions and when you can safely apply it. Sandy soils need different management than heavy clay soils.

Sandy soils lose nitrogen fast. Water moves through sand quickly, taking nitrogen with it, especially after heavy rains. If you farm sandy ground, split applications are essential – never put all your nitrogen down at once.

Clay soils hold nitrogen better but create different problems. They stay wet longer in spring, which can cause nitrogen to convert to gas and escape into the air. The good news is you have more flexibility with application timing on clay.

Poorly drained soils lose nitrogen through denitrification when they stay saturated. Standing water for three days at 70°F can cost you 12-15% of your applied nitrogen. Well-drained fields rarely have this problem.

Soil pH affects nitrogen availability too. When pH drops below 6.0, nitrogen conversion slows down, and your corn can’t access it efficiently. Extremely alkaline soils above pH 7.5 can cause ammonia volatilization, sending your nitrogen into the air.

How Can You Test If Your Corn Has Enough Nitrogen?

Testing helps you catch nitrogen problems before they hurt yields. By the time corn shows visual deficiency symptoms (yellow V-shaped patterns starting from bottom leaves), you’ve already lost 5-10% yield potential.

Soil Testing (PSNT)

The pre-sidedress nitrate test taken when corn is 12 inches tall tells you if you need additional nitrogen. Sample the top foot of soil and aim for 20-25 ppm nitrate-nitrogen. Below 20 ppm means you should apply more nitrogen immediately.

Tissue Testing

Pull the leaf opposite and below the ear from 15-20 plants when corn starts silking. Labs need samples within 24 hours for accurate results. You want to see 2.7-3.5% nitrogen content – anything below 2.5% means your corn is struggling.

Technology Tools

Chlorophyll meters and NDVI sensors compare your corn’s greenness to a well-fertilized reference strip. When readings drop below 95% of your reference, apply additional nitrogen.

Drone and satellite monitoring services now offer weekly field maps for $3 to $5 per acre. These services flag problem areas before visual symptoms appear, giving you time to apply rescue nitrogen through irrigation systems or high-clearance sprayers.

The key is catching deficiencies before the V10 stage. After that, rescue applications help but won’t fully recover lost yield potential.

What Happens With Too Little or Too Much Nitrogen?

Both nitrogen deficiency and excess hurt your bottom line, but deficiency costs more in lost yield while excess wastes money and creates environmental problems.

Too Little Nitrogen

Nitrogen-starved corn yields 20-50% less than properly fertilized fields.

The plant cannibalizes nitrogen from lower leaves to feed the ear, causing that telltale yellowing from bottom to top. Ears end up shorter with unfilled tips, and kernels lack protein content.

Too Much Nitrogen

Excess nitrogen beyond 220-250 pounds per acre rarely increases yields but always increases costs.

Over-fertilized corn stays green longer and delays maturity by 3-7 days. This pushes harvest into wet weather and increases drying costs. Stalks get weak and lodge easier in the wind, making harvest slower and reducing what you can actually collect.

Then there’s the environmental cost. Excess nitrogen leaches into groundwater or runs off into streams, contributing to water quality issues. Some states now require nitrogen management plans to prevent over-application.

The Bottom Line

Getting nitrogen right for corn means starting with a baseline of 1 pound per bushel of expected yield, then adjusting for what your soil provides naturally. 

Split applications give you flexibility to respond to weather while reducing loss risks.

Testing before sidedress tells you if you’re on track or need to adjust. 

The ideal nitrogen source depends on your equipment and application timing, but all forms work when managed properly.

Tyler O'Brien

Tyler is a results-driven marketing professional specializing in the industrial gases and equipment industry, bringing his 10 years of technical expertise and digital marketing acumen to the complex industrial gas B2B environment.