All posts by Nutifafa Adotey, Soil and Nutrient Management Extension Specialist

13 Mar 2025

Can we predict Corn N response using Mineralizable N?

13 Mar 2025
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Most of the soil nitrogen (N) is present in organic form, especially in the top 6 inches (75 – 95%), which is not readily available for plant uptake. Only about 0.1 – 0.3% is in inorganic or bioavailable forms such as nitrate and ammonium that plants can utilize. So, organic soil N is converted to inorganic forms for plants use, a process referred to as mineralization. The fraction of organic soil N that can be converted to inorganic form is referred to as potentially mineralizable N. Several factors including soil, previous crop, weather, and nitrogen management determine the extent of N mineralized. Nitrogen rate trials (>30) conducted over the past five years in West and Central TN suggested that mineralized soil N can contribute more than 20% of the total crop N requirements. Current N fertilizer recommendation for corn in Tennessee is based on realistic yield goals, which does not account for potentially mineralizable N that is available for the plant. Continue reading →


27 Feb 2025

Keeping an Eye on Soil Properties that Influence Ammonia Loss from UAN

27 Feb 2025
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Nitrogen management in most row crops can be a significant proportion of the overall production cost and can impact the bottom line. Keeping tabs on factors that can reduce the efficiency of N applications and deploying appropriate management strategies is one of the several ways to ensure a profitable production in this season. Nitrogen loss is one of the several factors that can reduce N application efficiency. The most common loss from broadcast or dribbled, unincorporated urea-containing fertilizers is ammonia volatilization losses, especially in no-till production systems. Ammonia volatilization occurs when ammonium ion from the breakdown of urea or fertilizer is subsequently converted to ammonia gas, which escapes to the atmosphere. The striking thing about ammonia volatilization losses is that nearly 90% of the total losses occurs within 3-5 days after fertilizer application. The potential and extent of ammonia loss is dictated by three key factors including soil properties, fertilizer management practices, and environmental conditions. This article focuses on how soil pH, clay content, soil organic matter, and soil moisture levels can influence ammonia loss from urea ammonium nitrate (UAN) applied onto the surface without incorporation.

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18 Feb 2025

Does Soil Test Phosphorus and Potassium Values from Haney Soil Health Test (H3A-4) Translate to Mehlich-3?

18 Feb 2025
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More recently, with emphasis on sustainable crop production, there are a number of tests that assess soil health. Some of the soil health tests such as the Haney Soil Health Tool (HSHT), which is adopted by USDA-NRCS, assess soil quality parameters as well as nutrient availability. The HSHT uses the H3A-4 extractant to estimate ‘plant available’ nutrients. The H3A-4 extractant simulates plant root environment by using organic acid plant exudates and has been touted as more representative of phosphorus availability. Some commercial soil testing laboratories offer HSHT and provide corresponding fertilizer recommendations. How does the test values and recommendations from H3A-4 relate to Mehlich-3 extraction? Publicly available information relating H3A-4 to Mehlich-3 extractable nutrients is limited. Continue reading →


14 Nov 2024

Post-harvest soil fertility consideration

14 Nov 2024
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Play podcast

In this podcast episode, Dr. Nutifafa Adotey and Dr. Jake McNeal addresses post-harvest soil and nutrient management questions sent in by local UT Extension agents.

You can learn more in the publications on estimating supplemental nitrogen following extended flooding and urease inhibitors, as referenced in the episode.

Check back soon for more segments covering topics related to soil and row crop agriculture!

 


03 Jun 2024

Nitrogen loss potential in wet corn fields

03 Jun 2024
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From late April and throughout the month of May, many parts of Middle and West TN have received persistent rainfall that is well above the average for this period. These rains have produced persistently wet soil conditions and have coincided with sidedress N fertilizer application where most or all of the recommended N is applied. With this much rain, there is potential for N loss. Continue reading →


12 Apr 2024

Estimating Sidedress N for Corn Fields with Poultry Litter Application

12 Apr 2024
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By Nutifafa Adotey, Assistant Professor & Soil and Nutr. Magt Specialist, Forbes R Walker, Professor & Envt. Soil Specialist, and Frank Yin, Professor & Cropping System Scientist, University of Tennessee

Poultry litter has become readily available to producers in Tennessee. However, poultry litter cannot supply all the nitrogen needed for corn and thus supplemental N is required to obtain optimal yield. The amount of supplemental N can be estimated using the Pre-Sidedress Nitrate Test. The Pre-Sidedress Nitrate Test is recommended only for corn producers using animal manure, poultry litter or biosolids, who want to estimate and fine-tune their sidedress N fertilizer applications following manure/poultry litter application. This article provides a guide for Tennessee corn producers using poultry litter on how to estimate sidedress N rate using the Pre-Sidedress Nitrate Test. Continue reading →


28 Mar 2024

Ammonia volatilization from unincorporated, surface-applied UAN on soils with pH >7

28 Mar 2024
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By Nutifafa Adotey, Assistant Professor & Soil and Nutr. Magt Specialist, Forbes R Walker, Professor & Envt. Soil Specialist, and Frank Yin, Professor & Cropping System Scientist, University of Tennessee

In Tennessee, the primary N fertilizer sources used are urea and urea ammonium nitrate (UAN). Other sources of N fertilizers, such as anhydrous ammonia, are used in some counties in Central and West Tennessee.  It is a known fact that ammonia volatilization from applied N fertilizers may occurs from (1) unincorporated, surface-applied urea-based fertilizer; (2) anhydrous ammonia due to poor equipment calibration; and (3) unincorporated, surface-applied ammonium-based fertilizer on alkaline soils. This N loss from these fertilizers is governed by a complex interaction of prevailing environmental conditions, soil properties and management practices. Soil properties determine the potential of ammonia loss while the extent of the loss is dictated by environmental conditions and management practices. Continue reading →


21 Feb 2024

Converting Between Mehlich 1 and 3 Soil Test Values for West Tennessee Soils

21 Feb 2024
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Most of the commercial and state soil testing laboratories in and around Tennessee use and prescribe fertilizer recommendations based on Mehlich 3 soil test extraction method. Most growers may receive soil test results from laboratories that utilizes Mehlich 3 soil test extraction method. However, The University of Tennessee gives fertilizer recommendations based on the Mehlich 1 extractant. This makes it difficult for growers to take advantage of The University of Tennessee fertilizer recommendations. Currently, the Mehlich 1 and 3 conversion equations used in TN were derived from the University of Kentucky, which were based on Kentucky soils (Table 1). Continue reading →