Predicting Field‐Apparent Nitrogen Mineralization from Anaerobically Incubated Nitrogen

Abstract

Core Ideas Study aimed to predict field N mineralization (N min ) from anaerobically incubated N (N an ). N an did not predict N min in areas with contrasting edaphic‐climatic properties. N min was predicted by a model including Nan, temperature and rainfall. The nitrogen (N) released after a 7‐d anaerobic incubation (N an ) 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 (N min ) of this pool. The objective of our study was to develop and validate a simple model to estimate N min from N an in corn ( Zea mays L.) and wheat ( Triticum aestivum L.) fields. To this end, we performed 100 field experiments where we measured N min , N an , rainfall, temperature (T C ), soil texture, pH, soil organic matter (SOM), and pre‐sowing mineral N concentration (N initial ). We performed a stepwise analysis to develop a model to predict N min using data from 70 sites, while the rest of the data was saved for model validation. The N an ranged from 16 to 94 mg kg –1 while N min ranged from 22 to 232 kg ha –1 . There was a strong association between N an and N min within regions with similar climate and edaphic properties. However, we could not fit a single significant model to estimate N min based solely on N an to be used in all regions. By considering other variables besides N an , we developed a model that allowed predicting N min independently from the site [N min = –252 + 12.3(T C ) + 1.37(N an ) + 0.27(rainfall)] ( R 2 = 0.89, model validation R 2 = 0.83). This model could be useful to adjust N fertilizer recommendations for corn and wheat, reducing the economic and environmental impact of fertilization.