Distinct interaction between management history and nitrogen source drive microbial nitrogen processes in soil

Microbial processes in soil primarily govern nitrogen (N) availability to plants. However, microbial processes can be altered by farming history due in part to resource adaptation by microbes and such changes could further modify N dynamics between fertiliser and plants. Here, using a two-months greenhouse experiment, we investigated plant N uptake from applied fertilisers as well as microbial parameters in N cycling modified by management history and fertiliser types. Sixteen soils were collected from either organically or conventionally managed fields and fertilised with ( 15 NH 4 ) 2 SO 4 (mineral N fertiliser) or 15 N- Lolium multiflorum (organic N fertiliser). Among microbial parameters tested, ammonia-oxidizing archaea ( amoA ) and membrane-bound nitrate reductase ( narG ) gene abundance responded to management × fertiliser interaction. Organically managed soils exhibited greater gene abundances with organic fertiliser compared to mineral fertiliser, and the opposite trend was observed with conventional management and mineral fertiliser. Plant fertiliser N uptake was associated with all microbial parameters tested, however, no positive interactions between management history and fertiliser type was observed. A clear management × fertiliser interaction effect was found exclusively in microbial biomass N with mineral fertiliser application where its association with plant N uptake was negative with organically managed soil but positive with conventionally manged soil at first harvest. Our results suggested that soil microbes are highly versatile and respond strongly to current nutrients conditions. Thus, fertiliser type and timing would be a key driver of short-term plant N uptake and warrant consideration to improve plant N recovery. • AOA amoA and narG had positive interaction between management history and N source. • Plant N uptake was associated with microbial biomass N, amoA , narG and chiA . • Nitrogen source rather than management history drove plant-microbe interaction.