首页|Plants with nitrate preference can regulate nitrification to meet their nitrate demand
Plants with nitrate preference can regulate nitrification to meet their nitrate demand
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NSTL
Elsevier
? 2021Plants with ammonium preference are able to exude biological nitrification inhibitors to reduce nitrification keeping the mineral N in NH4+ form. The question is whether plants with a NO3? preference are able to stimulate nitrification to shift mineral N towards NO3? production to meet their NO3? demand. In this study we attempted to solve this conundrum by conducting 15N tracing studies in a range of soils planted with wheat (Triticum aestivum L.), a typical NO3?-preferring crop, to quantify the gross rates of soil N transformations and the plant N uptake rates. Gross N mineralization rates (M) were stimulated by the presence of wheat in all studied soils, improving the mineral N supply. The wheat NH4+ uptake rates (UNH4) were significantly, positively correlated with M (p < 0.01). The wheat NO3? uptake rates (UNO3) were significantly higher than UNH4 confirming the NO3? preference of this plant. As NO3? production pathways we considered NH4+ oxidation (ONH4, the autotrophic pathway) and organic N oxidation to NO3?, ONrec) in this study. The stimulations of ONH4 were only observed in three out of five soils and, except one soil, ONH4 was much lower (average 1.29 mg N kg?1 d?1) than UNO3 (average 7.66 mg N kg?1 d?1) showing that the NO3? supply via this pathway was insufficient to meet the plants NO3? demand. In these soils, ONrec was significantly stimulated ranging from 0.86 to 5.52 mg N kg?1 d?1 and was responsible for 34%–74% of NO3? production during the 30 days experimental duration. Moreover, UNO3 was significantly, positively correlated with ONrec (p < 0.05), indicating a direct link between heterotrophic nitrification and plant NO3? uptake. One soil (SC2) exhibited a much higher ONH4 (>8.00 mg N kg?1 d?1) and only M was stimulated by the plants presence but not heterotrophic nitrification because the NO3? supply via ONH4 was sufficient to meet the plant NO3? demand. Heterotrophic nitrification was stimulated by NO3? preference plants when NO3? supply via oxidation of NH4+ to NO3? was insufficient to meet the NO3? requirements.
NSTL
Elsevier
