Predicting Corn N response using Alkaline Mineralizable N and Haney Soil Health Tool-N

Nutifafa Adotey, Xinhua (Frank) Yin, and Ryan Blair

Nitrogen management in corn production in the US is essential considering more than half the total N fertilizer used in the US is applied in corn production. Given the substantial investment in N fertilizer and its potential environmental risks, implementing best N management practices has potential to improve efficiency and profitability of applications. Nitrogen fertilizer recommendations for corn in TN as well as most southern US are determined from N response trials and modified based on soil type, previous crop and crop production history. Current N fertilizer recommendation does not account for potentially mineralizable N; hence, there is a possibility for either over or under application of N fertilizer. Limited information is available on the adequacy of alkaline mineralizable N or the mineralizable component of Haney test to predict corn response to N on replicated small plots in producer field in southern US. A crop response to mineralizable N may help develop a site-specific N fertilizer recommendation tool for corn, thus avoiding over or under application of N fertilizer. Replicated small plot on-farm trials are on-going at two locations in west TN to address the adequacy of alkaline mineralizable-N and HSHT -N to predict corn N needs”. The objectives of the on-farm trials include: (1) evaluating the relationship alkaline mineralizable N and HSHT to corn response, (2) developing N fertilizer rate calibration using alkaline-hydrolyzable N, and (3) comparing current UT fertilizer recommendation, HSHT N fertilizer recommendation, and alkaline-hydrolyzable fertilizer recommendation.

Evaluation of Urease and Nitrification Inhibitors in Corn Production

Nutifafa Adotey

Enhanced efficiency nitrogen fertilizers (EENF), recognized as a promising N management tool, reduces N loss, optimizes N uptake, improves crop productivity, maximizes profits, and reduces environmental pollution across various cropping system. Ammonia volatilization has long been recognized as a major N loss in several production system and among the factors that drive ammonia volatilization is application rates. Previous research on EENF often focus on either the recommended application rate or  below the recommended. Research based on corn response to EENF for both granular and liquid fertilizers is limited, hence the necessity to address this knowledge gap. A trial is ongoing to compare the EENF to standard N sources among various N sidedress placement methods on ammonia volatilization and grain yield in an unirrigated no-till corn production system. Treatment combinations consisted of N sidedress application of (i) urea to ANVOL-treated urea, and SuperU at increasing application rates (ii) UAN to ANVOL-treated at increasing application rates. The objectives of this project include evaluating the 1) inhibitory effect of urease inhibitors on ammonia volatilization from urea-based N fertilizers at increasing application techniques and 2) impact of urease inhibitors at reduced and optimal N application rates on corn agronomic and yield at increasing application rates.

Evaluating Side-dress Nitrogen Placement for Corn Grain Quality and Yield

Angela McClure, Xinhua (Frank) Yin, and Nutifafa Adotey,

itrogen (N) fertilizer is required at an adequate amount during the growing season for optimal seed quality and corn yield. A typical N management practice for most corn producers in TN is to split-apply a third of the recommended N at planting and sidedress the remaining N fertilizer. Currently, the commonly used N fertilizer sources by corn producers in TN are urea and urea ammonium nitrate (UAN) due to their economic advantage and minimal logistical constraints compared to other N sources. However, a major downside with these N sources is their susceptibility to N loss from ammonia volatilization. Broadcast or surface application of urea allows an applicator to cover a significant amount of acres in less time compared to UAN. However, UAN provides uniform application and is generally less susceptible to ammonia loss than urea. Depending on the N material and application technique used, a urease inhibitor may be beneficial and improve corn yields. In this work we are 1) evaluating the commonly used liquid and dry N materials with and without ANVOL urease inhibitor, 2) comparing typical UAN application methods (broadcast spray, row middle, Y-drop, in-ground behind coulter) for ease of use, N cost and yield, and 3) measuring N volatilization loss from surface UAN and urea treatments.

Evaluation of K Uptake, and Lint Yield Response to Cotton to Foliar K Fertilizer

Nutifafa Adotey, Xinhua (Frank) Yin, and Tyson Raper

Fertilization, especially potassium (K) is essential for quality fiber and optimal lint yield; hence, proper management of fertilizer K is critical to cotton farmers. However, late-season K deficiency in cotton is frequently reported in Tennessee (TN) and across the U.S. Cotton Belt. Some of these reported deficiencies have been observed in fields where soil test K levels are deemed sufficient for optimum yield. Generally, these K deficiencies are more noticeable from flowering through boll set, when the high demand for K exceeds the supply from the soil. The inherently low root density, as well as the slow root and shoot growth during boll development, have been reported as the main cause of the low supply of K. This may partly explain why some cotton plants show deficiency symptoms even in high K testing soils. Foliar application can be a useful means to correct K deficiency especially during the period of peak K demand at boll formation where logistical constraints and field conditions render soil application impractical or ineffective. Studies have evaluated the efficacy of foliar fertilizer application to correct K deficiencies in cotton fields across the U.S. Cotton Belt; however, there are discrepancies on the effectiveness of foliar K fertilization. The timing of foliar application and foliar solution chemistry may partly account for the differences in the performance of foliar K fertilizers. There is limited information comparing the efficacy of foliar fertilizer containing K and B or Zn at the recommended time with early bloom and 2 weeks after. In this project, we are evaluating the effect of foliar application timings and foliar K fertilizers (foliar K containing B and/or Zn) on K uptake, fiber quality, and lint yield.

In-lab Environment-Controlled System for Measuring Ammonia Volatilization

Nutifafa Adotey, Lori Duncan, Xinhua Yin, and Debasish Saha

Nitrogen is a major investment in agricultural production and a potential nonpoint source of pollution. A major challenge of N management is to minimize N losses and maintain optimal productivity with minimal environmental risks to other ecosystem functions and services. Ammonium-based fertilizers, the most commonly used N fertilizers in Tennessee, are relatively susceptible to volatilization losses compared to other N sources. However, there is limited information of the percentage of ammonia loss from urea-based fertilizers applied onto soils in Tennessee. A study that demonstrates the amount of N loss as ammonia across different soil types will encourage producers to pay close attention to their N management strategies and adopt efficient N management practices. Currently, an N management tool available to minimize N loss via ammonia volatilization is the enhanced efficiency fertilizers (EENF). There are myriad EENF products available on the market that reduce N loss via NH3 loss and N2O emissions, improves crop yield, and reduces environmental risks. However, evaluation of multiple products in a replicated unbiased field research is very expensive and restricted to the growing season. A rapid and precise environment-controlled system that provide reliable comparison between products on the market as well as ascertain the efficacy of newer products is a very useful tool. In this project we are constructing a controlled system to 1) evaluate ammonia volatilization from surface applied urea and urea ammonium nitrate (UAN) fertilizers applied to soils collected from 12 production fields with differing soil types, tillage practices, 2) evaluate the efficacy of selected EENF, 3) evaluate the performance of EENF at different moisture regimes, and 4) communicate the findings of research to Extension agents and producers as well as other relevant stakeholders.

Evaluating the impact of N Fertilizer Application Rates and Timings on Three Corn Varieties

Nutifafa Adotey and Ryan Blair

Nitrogen is the most yield limiting nutrients in corn production. A major challenge with N fertilizer recommendations is to accurately recommend N without over application to avoid unnecessary expense and increased N loss to the environments. In addition, producers in TN have raised concerns about the current fertilizer recommendation rates for corn, particularly N. Finally, an N response trial will generate addition data points for the N fertilizer calculator. We are conducting this project to accurately estimate the economically optimum nitrogen rate of three corn cultivar at multiple locations (Middle and West Tennessee).