Chemical and isotopic characterization of nitrate retained and leached from soil after manure fertilization-by lysimeter experiments

Increase of soil fertilization produces an increase of N exported to the hydrosphere. The amount of nitrate that reaches the aquifers is controlled by processes affecting N-species within the soils. The most relevant processes are nitrification, denitrification, assimilation, mineralization, and immobilization. This work studies the fate of N compounds in soil after manure application in a lysimeter study. To this end the isotopic composition of N and O of dissolved nitrate (δ15N-NO3- and δ18O-NO3-) was studied coupled with the evolution of N-compounds retained and leached from the soil. Results showed an increase in the δ15N-NO3- of the leached nitrate towards values similar to the δ15N-NH4+ from the applied manure. The highest δ15N-NO3- values were measured after 100 days of manure application, and thereafter, values decreased progressively towards the initial δ15N-NO3- of the soil before manure application.