The soil microbial community and plant biomass differentially contribute to the retention and recycling of urinary-N in grasslands
The soil microbial community and plant biomass differentially contribute to the retention and recycling of urinary-N in grasslands
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DOI：
10.1016/j.soilbio.2023.109011
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发表时间：
2023-03
影响因子：
9.7
通讯作者：
M. Reay;K. Marsden;Sarah Powell;Leonardo Mena-Rivera;D. Chadwick;Davey L. Jones;R. Evershed
中科院分区：
文献类型：
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作者：
M. Reay;K. Marsden;Sarah Powell;Leonardo Mena-Rivera;D. Chadwick;Davey L. Jones;R. Evershed
放牧系统中的尿斑是氮（N）循环和损失到更广泛的环境中的热点。尿氮的保留和随后的再循环是减少损失和提高生态系统氮利用效率的关键。微生物有机氮库的生物合成是一个重要的N途径，但这还没有直接量化的尿补丁。在此，我们提出了一个时间过程中的实验结果，使用土壤中生态系统播种多年生黑麦草（Lolium perenneL.）用15 N标记的绵羊尿处理土壤，研究了模拟降雨过程中施入的氮在植物、土壤生物量库和淋失之间的分配，并采用15 N示踪法和15 N-稳定同位素探针法（SIP）研究了尿氮的去向。最初较高的淋失量（233 kg N ha−1）包括分别通过尿素水解和硝化作用从尿液中提取的原生土壤氮、铵和硝酸盐。淋溶随后减少，而吸收到植物生物量和微生物生物合成增加在降雨量低的时期。吸收到地上和地下的植物生物量是最大的命运尿-15 N后94天（42%），虽然同化成微生物生物量占主导地位forca。1个月后尿沉积（34%）。化合物特异性15 N-SIP的氨基酸和氨基糖显示固定化尿氮矿化后的生物合成的主要途径，与细菌的有机氮池更快地比真菌的生物量纳入。还完整利用了来自尿液的甘氨酸。这项研究提供了明确的证据表明，直接同化尿来源的N进入微生物有机N库是一个重要的过程，为保留在尿补丁，这将随后支持植物N供应微生物周转。
Urine patches in grazed systems are hotspots for nitrogen (N) cycling and losses to the wider environment. Retention and subsequent recycling of urinary-N is key to minimise losses and increase ecosystem nitrogen use efficiency. Biosynthesis into the microbial organic N pool is an important N pathway but this has not been directly quantified in a urine patch. Herein, we present the results of a time course experiment using soil mesocosms sown with perennial ryegrass (Lolium perenneL.) and treated with15N-labeled sheep urine to determine partitioning of the applied N between plant, soil biomass pools and leaching losses following simulated rainfall events.15N-tracing used bulk and compound-specific15N-stable isotope probing (SIP) were used to determine the fate of urinary N. Initial high leaching losses (233 kg N ha−1) were comprised of native soil N, ammonium and nitrate derived from urine by urea hydrolysis and nitrification, respectively. Leaching subsequently decreased whilst uptake into plant biomass and microbial biosynthesis increased during periods of low rainfall. Uptake into above and belowground plant biomass was the largest fate of urinary-15N after 94 d (42%), although assimilation into microbial biomass dominated forca.1 month after urine deposition (34%). Compound-specific15N–SIP of amino acids and amino sugars revealed immobilisation of urinary-N following mineralisation was the dominant pathway for biosynthesis, with incorporation into bacterial organic N pools more rapid than into the fungal biomass. There was also intact utilisation of glycine derived from urine. This study provides clear evidence that direct assimilation of urine-derived N into microbial organic N pools is an important process for retaining N in a urine patch, which will subsequently support plant N supply during microbial turnover.