Project Overview
Commodities
- Agronomic: corn
Practices
- Crop Production: nutrient management
Abstract:
Current N fertilizer recommendation for corn in TN does not account for potentially mineralizable N; hence, there is a possibility for either over or under application of N fertilizer. A two-year field trial was conducted to assess the adequacy of alkaline mineralizable-N (AH-N), Haney's Soil Health Tool's plant available N, and Haney Soil Health Tool's estimated biological N (EB-N) to predict corn N needs. Two small plot on-farm trials were conducted at two locations in west TN in 2021-2023. Plots were four rows wide x 30 feet long and each treatment combinations were replicated four times in a randomized complete block design. The nitrogen fertilizer treatments included: 0, 60, 120, 180, 210, and 240 lb N ac-1. Before N fertilizer application, soil samples were collected from the 0 lb N ac-1 plots at different depths for soil health parameters using the Haney Soil Health Tool. In addition, soils were analyzed for alkaline mineralizable N. The specific objectives of the on-farm trials are to: (i) investigate the relationship between HSHT’s H3A-4 to Mehlich 3 extractable nutrient elements and (ii) evaluate the relationships of alkaline mineralizable N, HSHT plant available N, (iii) estimate the N rate required to attain the relative maximum grain yield at each location using the quadratic-plateau regression, (iv) evaluate the relationship between HSHT’s estimated biological N, HSHT’s Plant available N, and alkaline-hydrolyzable N to check plot grain yield, (v) develop N fertilizer rate calibration using alkaline-hydrolyzable N, and (vi) compare nitrogen fertilizer recommendations for optimum N rate to achieve 100% RGY, current University of Tennessee, Haney Soil Health Test, and alkaline-hydrolyzable mineralizable N. In 2021, a significant linear regression model was observed between the yield of check plots and AH-N at all depth, with the best predictive relationship at the 6-12-inch depth (R2 = 0.57). With the exception of the 0-6 and 0-24-inch depths, a strong relationship was observed between the yield of check plots and AH-N for the other depths in 2023. In contrast, a strong relationship was not observed between grain yield from the check plots and HSHT’s Plant available N or HSHT’s estimated biological N regardless of year. A calibration of AH-N for the 0-6, 6-12, 12-18-inch depth to predict the N rate required to achieve 100% relative grain yield was generated. The recommended N rate from AHN was similar to the optimum N rate, which were both lower than current recommendations from HSHT and the current recommendations by University of Tennessee. However, caution must be exercised considering the limited number of data points used to generate this model. Continuing research on a correlation and calibration curve to generate additional data points are required to make this model robust.
Project objectives:
A replicated small plot on-farm trial will be conducted at two locations in west TN to address the adequacy of alkaline mineralizable-N and HSHT -N to predict corn N needs”. The specific objectives of the on-farm trials are to: (i) investigate the relationship between HSHT’s H3A-4 to Mehlich 3 extractable nutrient elements and (ii) evaluate the relationships of alkaline mineralizable N, HSHT plant available N, (iii) estimate the N rate required to attain the relative maximum grain yield at each location using the quadratic-plateau regression, (iv) evaluate the relationship between HSHT’s estimated biological N, HSHT’s Plant available N, and alkaline-hydrolyzable N to check plot grain yield, (v) develop N fertilizer rate calibration using alkaline-hydrolyzable N, and (vi) compare nitrogen fertilizer recommendations for optimum N rate to achieve 100% RGY, current University of Tennessee, Haney Soil Health Test, and alkaline-hydrolyzable mineralizable N