Evaluation of Distillation and Diffusion Techniques for Estimating Hydrolyzable Amino Sugar‐Nitrogen as a Means of Predicting Nitrogen Mineralization

Abstract

A rapid method to estimate soil N mineralization to improve N fertilizer recommendations has long been sought. Over the years, numerous methods to predict N mineralization have been proposed, but no one method has been widely accepted. Recently, researchers observed the concentration of hydrolyzable amino sugar‐N in the soil correlated with crop N response. The objective of this study was to determine if developmental methods that quantify hydrolyzable amino sugar‐N accurately predict N mineralization when compared to net‐N mineralization by anaerobic incubation. Methods evaluated to predict hydrolyzable amino sugar‐N were the Illinois soil nitrogen test (ISNT) by diffusion, and 2, 5, and 10 M NaOH direct steam distillation procedures. It was observed that the hydrolyzable amino sugar‐N was a somewhat accurate predictor of N mineralization (R2 = 0.38). However, when the hydrolyzable amino sugar‐N concentrations were combined with the hydrolyzable NH4–N concentrations, the ability to predict N mineralization improved (R2 = 0.61). Suggesting more labile soil organic N forms along with amino sugar‐N are potentially mineralizable. Rapid analytical procedures like the ISNT diffusion method and the 2, 5, and 10 M NaOH direct steam distillation techniques accurately predicted hydrolyzable amino sugar‐N as well as hydrolyzable (NH4 + amino sugar)‐N. These methods also accurately predicted NH4–N mineralized after anaerobic incubation. It could be assumed that this predictability may increase when soils are analyzed based on soil management, geographic area, and crop rotation. Glucosamine recovery was significant ( >85%, P = 0.05) for both methods showing their ability to quantify amino sugar‐N in the soil as well as estimate the amount of potentially mineralizable‐N. Lastly, in soil‐testing facilities where the ISNT is already implemented as a procedure, the much quicker and equally reliable 10 M NaOH distillation technique may be used to achieve near identical test values.

Mild and Moderate Extraction Methods to Assess Potentially Available Soil Organic Nitrogen

“…In Brazil, Otto et al (2013) considered ISNT a promising index for estimating potential responses to N fertilization in sugarcane cropping areas. An alternative method to ISNT is direct distillation (Bushong et al, 2008;Roberts et al, 2009), which exhibited similar extraction capacity and high correlation coefficients with ISNT (Bushong et al, 2008;Roberts et al, 2009;Otto et al, 2013); in addition, direct distillation does not require the use of Mason Jar, a container not readily available in the Brazilian market and which might limit adoption of the method.…”

Assessing Indices for Predicting Potential Nitrogen Mineralization in Soils under Different Management Systems

“…Correlations methods Hot_N and Hyd_N were more strongly correlated with among chemical methods were similar to correlations between soil organic C and TN than were the biological indicators aerobic chemical and biological methods (Table 5) - mg kg −1 Table 1. ‡ Tillage abbreviations as in Table 2 and for soil management effects (Bushong et al, 2007(Bushong et al, , 2008Soon et al, 2007). It is a more standardized, simpler, and quicker procedure than the long-term aerobic incubation procedure.…”

“…Soon et al (2007) also found a strong correlation between Nmin_24 and Ana_N (r = 0.90). Several authors have suggested the 7-d anaerobic incu bation is the best biological indicator of potentially available N (Bushong et al, 2007(Bushong et al, , 2008Soon et al, 2007). Values of N 0 determined with the single exponential equation for each soil-tillage-depth combination ranged from 35 mg N kg −1 soil for the 5-to 15-cm depth of the convention ally tilled Tifton soil to 488 mg N kg −1 soil for the 5-to 15-cm depth of the no-till Cecil soil having a long history of poultry litter application (Table 4).…”

Field Validation of N-STaR for Rice Produced on Silt Loam Soils in Arkansas

“…Roberts et al (2011) was successful in developing a direct steam distillation method (Bushong et al, 2008;Roberts et al, 2009) that was highly correlated with rice total N uptake as well as RGY per-centage. The successful development of a calibration curve was achieved and resulted in a high coefficient of determination (r 2 = 0.89), but soils had to be sampled to a depth of 45 cm, which appears to be the effective rooting depth of rice grown on silt loam soils in Arkansas (Roberts et al, 2011).…”

“…Soil-water pH was measured with a glass electrode in a 1:2 soil/water (w/v) mixture. The direct steam distillation procedure as outlined by Bushong et al (2008) and Roberts et al (2009) was used to obtain the N-STaR soil test level, which involves a 7 min distillation using 10 mol L −1 NaOH. Nitrogen rate recommendations were determined using the N-STaR soil test value and N rate calibration equations that provided the N rates necessary to achieve 90, 95, and 100% RGY within a given location and correspond to N-STaR 90, 95, and 100% RGY, respectively, adapted from Roberts et al (2011) …”