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

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

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


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

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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


What are the Soil Nitrate Levels after Drought followed by Late Season Rainfall?

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The unusually dry soil conditions during most part of the growing season this year limited nitrogen (N) uptake and lessened the potential for N loss through denitrification or leaching. Intuitively, the unused N, which would be in the nitrate form may remain in the soil. However, since August, there has been considerable amounts (more than 12 inches) of rainfall which can affect the availability of nitrate-N. This has raised questions about how much nitrate-N would be available in the soil after drought and late season rainfall? Continue reading


Impact of Drought on Residual Soil Nitrate

Abnormally dry soil conditions as a result of rainfall amounts far below average during this corn growing season present unique nutrient management decisions after harvest, particularly for growers considering wheat crop this fall. This article will address two key questions that may come handy in making management decisions: Is there be considerable amounts of residual soil N left after the 2022 corn crop? and if the residual soil nitrate is sufficient to meet N demand of the wheat crop in the fall? Continue reading


Nutrient Management in Cotton During Drought Conditions

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Due to the ongoing drought, I’ve recently received questions along the lines of, “how much N is still available after the prill sits on the soil surface without rain for 35 plus days?” and, “should I begin a foliar fertilizer regiment to meet plant N/K/S/B demands?”  In this blog, I tackle both of these questions and share N response curves generated from Tennessee data over the past 5 years.

“I applied urea and it didn’t rain for a month.  Will my cotton crop have the N required to make close to maximum yields?”

For growers that have applied 60-90 lb as urea, the simple answer is yes; the amount of soil nitrate released from the urea you applied will likely meet cotton N demand without additional N fertilizers given plant available water increases significantly in the coming week. Generally, if surface applied urea fertilizer is not incorporated into the soil, some of the N may be lost as ammonia into the atmosphere depending on weather, soil properties and management practices. Continue reading


In-season Plant Testing Interpretation During Dry Soil Conditions

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In season plant tissue testing helps producers monitor plant nutrition and can be useful in diagnosing nutrient deficiency.  Detecting deficiencies early can allow the corrective or preventive action that will minimize yield effects from deficiency during the growing season. Nutrient concentrations vary greatly with plant growth stages and the part of the plant that is sampled so specific sampling guidelines and interpretation have been instituted to prevent false diagnosis. Continue reading


2022 Certified Crop Adviser of the Year

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 The nomination for the CCA of the Year is still open. This is a great opportunity to honor a CCA personnel in TN for their exceptional customer service, innovations, substantial contribution to the exchange of ideals and the transfer of agronomic knowledge within the agricultural industry.

The Tennessee Farm Bureau along with the Tennessee Certified Crop Adviser Board of Directors sponsor an Award to a deserving Tennessee Certified Crop Adviser who has exemplified the merits of service and dedication to their customers.

The winner will receive a plaque and a $500 cash prize.

To nominate someone, please write a short bio of this person’s accomplishments and submit to Jaymie Seay, Executive Board Administrator for the Tennessee CCA Board of Directors. Her email is Jaymie.seay@protritionfeed.com   You do not have to be a CCA to nominate someone. Please submit by August 30, 2022.

A committee from the Tennessee CCA Board will select the winner.


Management Practices to Optimize Nitrogen Fertilizer Use with High Fertilizer Prices

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Nitrogen (N) fertilizers may be a limiting factor for corn production based on rising N fertilizer prices and other production input. There are a few things to consider with high N fertilizer prices: (a) apply N fertilizer at the right time, (2) add or treat urea-based fertilizers with a proven N stabilizer, and (3) apply the N fertilizer at the appropriate N rate.

Apply N fertilizer at the right time

Preplant N application in corn is not recommended in Tennessee because of the length of time from application to when the corn plant will begin significant N uptake. One exception is the application of anhydrous ammonia with properly calibrated equipment. Corn plants take up little N (<12% of N uptake during the growing season) until V6 growth stage, with the most active period of N uptake occurring between V8 to V14. Hence, there is a greater risk for N loss via ammonia volatilization or nitrate leaching from preplant N. Split application is recommended when N rates are greater than 120 lb N/A. A typical split management practice is to apply a third of the total intended N per acre at planting and sidedress the remaining N fertilizer between V4 to V6. Split application also provides flexibility to adjusting N rate during growing season as compared to just a single application at planting. Split-application of a third of the recommended N at planting and sidedress the remaining N fertilizer provides greater yield than single application at planting (Figure Below-average across six trials). Continue reading