Deep Soil Testing Can Reduce Input Costs Amid High Fertilizer Prices

Accounting for in-soil nitrogen can offset some high crop production expenses

Farmers should consider deep soil testing for residual nitrogen and other nutrients, especially when rising fertilizer prices impact profit potential, according to a team of Texas A&M AgriLife Extension Service specialists.

The team of AgriLife Extension economists and agronomists published new findings after analyzing the benefits of soil testing before planting corn, cotton or wheat. They projected savings of anywhere from $12 to $150 per acre were possible by taking advantage of the residual nitrogen already in the soil before making growing season decisions.

DeDe Jones, AgriLife Extension risk management program specialist in the Texas A&M Department of Agricultural Economics at the Texas A&M AgriLife High Plains Research and Extension Center in Canyon, said the report could represent significant savings for producers as fertilizer costs have jumped over recent months.

Jones provided an example of these fertilizer price increases based on data from local dealers and noted that cost increases will vary by region:

• Nitrogen dry 46-0-0 went from $545 per ton in December to $730 per ton in March, a 34% increase.
• Nitrogen liquid 32-0-0 went from $455 per ton in December to $510 per ton in March, a 12% increase.
• Anhydrous NH3 went from $710 per ton in December to $900 per ton in March, a 27% increase.

“We know, due to high 2026 production costs and low commodity prices, it is well worth spending around $2.50 per acre for deep soil testing,” Jones said. “With the return on investments that we project, testing is a very smart decision.”

Necessary nitrogen might be in the ground already
Fertilizer applications optimize crop yields by supplementing the available plant nutrients to meet crop fertility needs, but producers often don’t consider residual nutrients present in the soil, said Jourdan Bell, Ph.D., AgriLife Extension agronomist and professor in the Department of Soil and Crop Sciences at the Texas A&M AgriLife High Plains Research and Extension Center.

Jones and Bell recently finalized a study, “Deep Soil Testing Offers the Potential to Reduce Fertilizer Costs.”

“This study shows that even small investments or minor operational changes can lead to large financial savings,” Jones said. “We demonstrate how deep soil testing allows producers to take advantage of nitrogen already present in the soil and apply less fertilizer.”

Soil testing beyond 6 inches
Bell said that while annual soil testing is standard for monitoring nitrogen and essential nutrients, timing is everything.

“Sampling near planting is the goal, though scale and field conditions can get in the way,” she said. “The closer to planting you sample, the better your data, particularly for nitrogen, which can be immobilized and may actually be unavailable if tested too far in advance.”

Soil sampling should be conducted at approximately the same time every year to accurately account for the natural cycling of nutrients in and out of the soil, Bell said.

Producers typically only sample the top 0-6 inches, but deep soil sampling to depths of 6-24 inches or deeper, if feasible, should be done when possible, she said.

This allows producers to better utilize the nitrogen below the upper 6 inches of soil.

In addition to reducing fertilizer input costs, she said proper nitrogen management in crop production systems also can impact the need for and rates of other inputs.

“For example, in cotton, we know that nitrogen in excess of the crop demand can cause aggressive plant growth, so producers have to be more aggressive with their plant growth regulators program,” she said. “There is both an input and production cost.”

Excess nitrogen can also delay cotton maturity, which can impact growing-day-limited cotton regions such as the Texas Panhandle, Bell said. So, producers must be aware of residual nitrogen not just to optimize input costs, but also to optimize production.

Deep sampling provides a powerful tool to assess the entire nutrient profile and can protect the bottom line by providing the knowledge necessary to make data-driven decisions, she said.

“We know residual plant nutrient levels in the soil can vary greatly from year to year based on many factors, including fertilizer application rates, rainfall, irrigation, cropping system and prior year crop uptake,” Bell said. “That is why annual sampling is important.”

Both specialists agreed that while this was only one year’s worth of data, it highlights the potential for cost savings.

The savings add up
While crop development depends on many nutrients, proper nitrogen application is critical as it is generally the most limiting nutrient. Prices for nitrogen fertilizer products have been very volatile in recent years due to high natural gas prices, supply chain disruptions and trade disputes.

Corn production shows the greatest benefit from reduced fertilization expenses because it has the highest nitrogen application rates, ranging from $40 per acre with a 25% residual to almost $150 per acre for a 100% residual, Jones said.

Cotton registered the second-highest advantage, with cost savings ranging between $25 and $97 per acre. Wheat shows the least benefit, in a lower-yielding environment, due to low nitrogen application rates compared to the other crops, falling between $12 and $42 per acre.

“Our results show that taking advantage of even relatively low levels of residual nitrogen can make a big difference to the bottom line,” she said. “For example, if a producer applies only 75% of their budgeted nitrogen because testing shows 25% is already in the soil, they can save over $26,000 on 1,000 acres of irrigated farmland.”