Phosphorus availability and plants alter soil nitrogen retention and loss

摘要

Availability of phosphorus (P) can directly and/ or indirectly affect nitrogen (N) retention and loss from soil by stimulating microbial and plant root activities. However, it is not clear how P availability and plant presence interact on nitrous oxide (N2O) emission and nitrate (NO3-) leaching in soil. A mesocosm experiment was conducted to investigate the effect of P addition (0, 10 and 20 mg P kg(-1)) with and without plant presence (Phalaris aquatica, C3 grass) on N2O emission, NO3- leaching and N-15 recovery. Our results showed large variation in N2O emission with significant increases after leaching events. We observed that initially low but later (after 53 days of sowing) high levels of P addition increased N2O emission rates, possibly by stimulating nitrifiers and/ or denitrifiers in soil. Plant presence decreased N2O emission at times when plants reduced water and NO3- in the soil, but increased N2O emission at times when both water and NO3- in the soil were abundant, and where plants may have stimulated denitrification through supply of labile organic C. Furthermore, an increase in net N mineralization, possibly due to increased decomposition stimulated by root derived C, may also have contributed to the higher cumulative N2O emission with plant presence. P addition increased N-15 recovery in soil, but reduced it in leachates, suggesting increased N-15 fixation in microbial biomass. Our results showed that both P addition and plant presence stimulated N loss as N2O, but also increased N retention in the soil-plant system and thus reduced N loss through leaching. (C) 2019 Elsevier B.V. All rights reserved.