Modeling hot-spot of N2 and N2O production in agricultural soils as introduced by liquid organic fertilization

Prediction of liquid organic fertilizer effects by biogeochemical models on denitrification and associated N₂O and N₂ fluxes in soils is inappropriate, because previous studies mostly excluded N₂, and the calibration of the models without N₂ data is inaccurate. Besides, the models mostly homogenize the substrate content of the applied manure with the corresponding substrate pools of the soil, without the consideration of the effects of the liquid manure induced hot-spots in the soil. Therefore, the main goal of the MOFANE Project was to develop a new approach dealing with hot spot effects in manure amended soils. A simple and static model approach (Sommer et al., 2004) was improved and developed for a dynamic model to consider the effect of the manure induced hot-spots in the soils. It contemplates the effect of the application technique of the liquid manure (surface or injected), the ammonium and labile organic carbon content of the manure, the water content and the structure of the soil to calculate the NH₃ loss, the N mineralization and O₂ consumption of the degradable organic content, the nitrification and the denitrification in the manure-soil hot-spot region. The substrate exchange and flow are calculated based on the water potential difference between the liquid manure and soil. A laboratory experiment was conducted to provide proper input and output data for the model testing.  A sandy (Grosz et al., 2022) and a loamy arable soil were investigated in 10 days laboratory incubations. The temperature was constant 15^oC and the water-filled pore space (WFPS) were constant 40% and 60%. The soils were amended with and without artificial slurry in three manure treatments (control, surface-applied, injected). N₂O and CO₂ fluxes were quantified by gas chromatography. N₂ and source-specific N₂O flux was quantified by isotope-ratio mass spectrometry. The results of laboratory experiments will be used for testing the model accuracy. 

Grosz, B., Kemmann, B., Burkart, S., Petersen, S. O., and Well, R.: Understanding the Impact of Liquid Organic Fertilisation and Associated Application Techniques on N₂, N₂O and CO₂ Fluxes from Agricultural Soils, Agriculture, 12, 692, https://doi.org/10.3390/agriculture12050692, 2022.

Sommer, S. G., Petersen, S. O., and Møller, H. B.: Algorithms for calculating methane and nitrous oxide emissions from manure management, Nutrient Cycling in Agroecosystems, 69, 143–154, https://doi.org/10.1023/B:FRES.0000029678.25083.fa, 2004.