Soil and nitrogen management with Dr. Alan Blaylock

Sandy loam - soil background, texture

Soil is the foundation for every growing crop. Knowing how to manage nutrients for the soil type on your farm is key to optimizing crop performance and yields. From diagnostic tools to nitrogen fertilizer sources, Nutrien Senior Agronomist Dr. Alan Blaylock shares his insights on soil and nitrogen management.

What are the benefits of proper nitrogen levels, or a balanced soil?

Proper nitrogen levels are critical to achieving economically optimum crop performance. Insufficient nitrogen causes crop yield and quality losses. Excess nitrogen leads to more losses, inefficiency, reduced crop quality, greater lodging potential, delayed maturity, economic loss, and other potential problems. Because nitrogen has such large effects on crop performance, it is important to do the best we can with this input. We must also remember the need to balance other nutrients and eliminate other yield-limiting factors. If other factors are limiting yield, the crop will not make full use of the nitrogen that is applied. Nitrogen should not be considered as independent of other nutrients. Phosphorus, potassium, and sulfur are also commonly needed in corn-producing areas. Appropriate balance with these nutrients can help get maximum benefit of the applied nitrogen.

Besides soil sampling, what signs can growers look for to identify nitrogen loss in soil? How can they test or determine if they are nitrogen deficient and how much they are losing?

Exactly how much nitrogen has been lost is difficult to know at the time of the loss event. Soil sampling is not a particularly reliable indicator in humid regions, unless you have a sample before and after a loss event. Soil samples may be more useful in drier regions.

Loss can be highly variable across a field. Soils that have ponded water for more than a few days can lose 30-50% of nitrogen applied before the ponding. Significant rains of several inches or more may cause leaching losses of similar magnitude on sandy soils. Following loss events, you may observe yellow areas of fields where loss has been greater than in other areas because of differences in drainage or infiltration rates. Once the crop is established, growers should monitor crop appearance. While symptoms are not a completely reliable indicator  (other disorders or other nutrient deficiencies can have similar symptoms) a general yellowing of the crop starting with lower leaves is a good indicator of nitrogen deficiency.

Some diagnostic tools, such as a “pre-sidedress soil nitrate” test can be informative if properly calibrated for the crop. Plant leaf sampling can sometimes give a good estimate of plant nitrogen status if proper levels are known and even better if a healthy comparison sample is available. Some scientists have advocated aerial imagery or other crop color assessments are good indicators of crop nitrogen status.  One practice that is particularly informative is to include what is called a “nitrogen-rich” test strip, which is a strip that is fertilized at a rate you know will not be deficient. The rest of the field can then be compared visually, by leaf analysis, or by remote imagery to this strip. If using a sensing technology, the crop color can be quantified and compared numerically to the test strip. Areas of the field that are less than about 90-95% of the check-strip greenness should be considered for additional nitrogen.

How does ESN work to restore nitrogen in soil? How does this work differently than other fertilizers?

ESN is different from other nitrogen fertilizers in that it supplies nitrogen to the crop over time. This reduces the exposure to early season nitrogen losses, which is often the period of greatest risk. It also supplies nitrogen to the crop at a somewhat steady rate, regulated by factors that also drive crop growth and nitrogen demand. The result is less nitrogen loss, more consistent nitrogen supply to the crop, more constant nitrogen availability in the soil, closer synchronization of nitrogen supply with crop demand, and improved nitrogen-use efficiency.

According to research, ESN offers the greatest benefits to soils with low organic matter and higher moisture levels. Are there any other soil conditions that would benefit from ESN?

Low organic-matter soils typically have lower soil-nitrogen supply from mineralization. These soils are particularly sensitive to nitrogen deficiency from losses, so prevention of those losses with ESN can provide large benefits. In contrast, high organic matter soils may mitigate losses by mineralization of soil organic nitrogen and therefore have greater buffering against losses. Greater precipitation and wetter soils are more conducive to nitrogen loss because excess moisture is a primary driver in leaching and denitrification losses. The greater potential for nitrogen loss, the greater the benefit of tools that reduce the loss, like ESN. The combination of excess moisture and low soil organic matter is a combination that is particularly responsive to practices and products that reduce nitrogen loss. With that said, any soil and environmental conditions that are prone to nitrogen loss will benefit from ESN’s protective properties. Sandy soils, irrigated cropping systems, poorly drained soils, and tile-drained soils are some of the conditions that may contribute to nitrogen loss and could benefit from using ESN.

How can growers who apply ESN see improvements in their crops?

The best evidence of ESN’s benefits is in the final yield and profitability of the crop at harvest. Other improvements you may observe are less “firing” of lower leaves (a symptom of nitrogen deficiency), generally better crop color (greenness), better tip fill on corn ears, and longer persistence of crop greenness throughout the growing season, especially into the grain fill period.

To learn more about nitrogen management and ESN, check out our ESN Education webinars and learning modules.

Do you have a specific question about ESN? Tweet us @SmartNitrogen or Ask the Agronomist.