Microbial competition for nitrogen and carbon is as intense in the subsoil as in the topsoil
Microbial competition for nitrogen and carbon is as intense in the subsoil as in the topsoil
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DOI：
10.1016/j.soilbio.2017.10.024
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发表时间：
2018-02-01
影响因子：
9.7
通讯作者：
Murphy, D. V.
中科院分区：
文献类型：
--
作者：
Jones, D. L.;Magthab, E. A.;Murphy, D. V.
大多数关于植物营养的研究往往集中在表层（耕作层），而经常忽视底土过程。然而，谷物根系可以从土壤剖面深处获得包括有机和无机氮（N）在内的营养物质。需要更多地了解植物和微生物在底土环境中的相互作用，以评估谷物的深根特性是否会在种植系统中实现更高的养分利用效率和更大的土壤碳（C）储存。本研究旨在评估在小麦种植周期的关键生长期，在砂质地的Eutric形成土的根系分布，有机和无机氮的有效性和潜在的氮供应之间的关系。我们的研究结果提供了证据，显着的微生物能力在底土。随着土壤深度的增加，植物残体周转率和有机C和N基质（葡萄糖，氨基酸，肽，蛋白质）的矿化略有下降，但这些速率与基础土壤呼吸，微生物生物量或群落结构无关。这表明，在底土中的微生物种群是更多的C限制，但它的活性可以很容易地刺激后C基板添加。有机和无机氮周转的一个显着的潜力也表现在深度与类似丰度的氨化和氨氧化细菌（AOB）和古菌（AOA）在整个土壤剖面。再次，氮矿化在底土似乎是基板限制。根系密度沿土壤剖面迅速下降，超过50厘米的根系很少;这表明这是限制底土中土壤有机质和微生物活性的C补给的主要因素。更大的根增殖在深度可以更大的水的捕获和N的回收流失的浸出，但是，我们的研究结果表明，植物微生物的C和N的竞争是激烈的底土在表土。我们的结论是，虽然更深的生根可能会提高养分和水分的利用效率，它可能不会导致更大的C封存在底土，至少在短期内。
Most studies on plant nutrition tend to focus on the topsoil (plough layer) and frequently neglect subsoil processes. However, cereal roots can potentially acquire nutrients including organic and inorganic nitrogen (N) from deep in the soil profile. Greater knowledge on the interaction of plants and microbes in subsoil environments is required to evaluate whether deep rooting traits in cereals will achieve greater nutrient use efficiency and greater soil carbon (C) storage in cropping systems. This study aimed to evaluate the relationship between root distribution, organic and inorganic N availability and potential N supply at the critical growth period during the wheat cropping cycle in a sand textured Eutric Cambisol. Our results provide evidence of significant microbial capacity in the subsoil. The rate of plant residue turnover and the mineralization of organic C and N substrates (glucose, amino acids, peptides, protein) declined slightly with increasing soil depth; however, these rates were not correlated with basal soil respiration, microbial biomass or community structure. This suggests that the microbial population in subsoil is more C limited but that its activity can be readily stimulated upon C substrate addition. A significant potential for organic and inorganic N turnover was also demonstrated at depth with a similar abundance of ammonifiers and ammonia oxidizing bacteria (AOB) and archaea (AOA) throughout the soil profile. Again, N mineralization in subsoils appears to be substrate limited. Root density declined rapidly down the soil profile with few roots present past 50 cm; suggesting that this is the major factor limiting C recharge of soil organic matter and microbial activity in subsoils. Greater root proliferation at depth could allow greater capture of water and the recapture of N lost by leaching; however, our results suggest that plant-microbial competition for C and N is as intense in the subsoil as in the topsoil. We conclude that while deeper rooting may improve nutrient and water use efficiency it may not lead to much greater C sequestration in subsoils, at least in the short term.