Predicting field‐apparent nitrogen mineralization from anaerobically incubated nitrogen

Abstract

The nitrogen (N) released after a 7-d anaerobic incubation (Nan) is a good estimator of the size of the soil N mineralizable pool. However, there is a lack of information on how soil properties and climate affect the apparent field N mineralization (Nmin) of this pool. The objective of our study was to develop and validate a simple model to estimate Nmin from Nan in corn (Zea mays L.) and wheat (Triticum aestivum L.) fields. To this end, we performed 100 field experiments where we measured Nmin, Nan, rainfall, temperature (TC), soil texture, pH, soil organic matter (SOM), and pre-sowing mineral N concentration (Ninitial). We performed a stepwise analysis to develop a model to predict Nmin using data from 70 sites, while the rest of the data was saved for model validation. The Nan ranged from 16 to 94 mg kg-1 while Nmin ranged from 22 to 232 kg ha-1. There was a strong association between Nan and Nmin within regions with similar climate and edaphic properties. However, we could not fit a single significant model to estimate Nmin based solely on Nan to be used in all regions. By considering other variables besides Nan, we developed a model that allowed predicting Nmin independently from the site [Nmin = -252 + 12.3(TC) + 1.37(Nan) + 0.27(rainfall)] (R2 = 0.89, model validation R2 = 0.83). This model could be useful to adjust N fertilizer recommendations for corn and wheat, reducing the economic and environmental impact of fertilization.