首页|Nitrogen and phosphorus availability have stronger effects on gross and net nitrogen mineralisation than wheat rhizodeposition
Nitrogen and phosphorus availability have stronger effects on gross and net nitrogen mineralisation than wheat rhizodeposition
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NSTL
Elsevier
Soil nitrogen (N) availability is determined by microbial gross N mineralisation (GNM) and immobilisation, where net N mineralisation (NNM) represents their balance. Plants provide a substantial amount of their photosynthesized C belowground into the soil as rhizodeposition, which can stimulate microbial activity affecting GNM and NNM, but this activity also depends on soil N and phosphorus (P) availability. We examined how N (25 and 100 kg N ha(-1) or 44 and 177 mg N pot(-1 )) and P (10 and 40 kg P ha(-1), or 18 and 71 mg P pot(-1)) fertilisation affected microbial N mineralisation in soil planted with two wheat genotypes (Suntop and 249) varying in root biomass and rhizodeposition. We used a continuous (CO2)-C-13 labelling method to track plant C rhizodeposition and a N-15 pool dilution technique to investigate GNM. We further assessed NNM by comparing N pools in plant and soil at the start and end of the experiment. We observed increased GNM with increased P fertilisation, likely because of P-induced N limitation stimulating microbial mining for N, particularly at the low level of N fertilisation. N fertilisation did not affect GNM but the higher level of N fertilisation reduced NNM, likely because of increased microbial immobilisation of fertiliser N. Our results suggest that GNM was more sensitive to soil N and P availability than to rhizodeposition between wheat genotypes, although at high N fertilisation, rhizodeposition contributed to reduced NNM, likely because rhizodeposition enhanced microbial N immobilisation. We conclude that the relative availability of N and P in soil should be considered for managing GNM and NNM in soil.
NSTL
Elsevier
