Reichel Rüdiger, Wei Jing, Islam Muhammad S, Schmid Christoph, Wissel Holger, Schröder Peter, Schloter Michael, Brüggemann Nicolas
Forschungszentrum Jülich GmbH, Institute of Bio- and Geosciences, Agrosphere (IBG-3), Jülich, Germany.
General and Theoretical Ecology, Institute of Ecology, University of Bremen, Bremen, Germany.
Front Plant Sci. 2018 Jun 28;9:900. doi: 10.3389/fpls.2018.00900. eCollection 2018.
Plants like winter wheat are known for their insufficient N uptake between sowing and the following growing season. Especially after N-rich crops like oilseed rape or field bean, nitrogen retention of the available soil N can be poor, and the risk of contamination of the hydrosphere with nitrate (NO) and the atmosphere with nitrous oxide (NO) is high. Therefore, novel strategies are needed to preserve these unused N resources for subsequent agricultural production. High organic carbon soil amendments (HCA) like wheat straw promote microbial N immobilization by stimulating microbes to take up N from soil. In order to test the suitability of different HCA for immobilization of excess N, we conducted a laboratory incubation experiment with soil columns, each containing 8 kg of sandy loam of an agricultural Ap horizon. We created a scenario with high soil mineral N content by adding 150 kg NH-N ha to soil that received either wheat straw, spruce sawdust or lignin at a rate of 4.5 t C ha, or no HCA as control. Wheat straw turned out to be suitable for fast immobilization of excess N in the form of microbial biomass N (up to 42 kg N ha), followed by sawdust. However, under the experimental conditions this effect weakened over a few weeks, finally ranging between 8 and 15 kg N ha immobilized in microbial biomass in the spruce sawdust and wheat straw treatment, respectively. Pure lignin did not stimulate microbial N immobilization. We also revealed that N immobilization by the remaining straw and sawdust HCA material in the soil had a greater importance for storage of excess N (on average 24 kg N ha) than microbial N immobilization over the 4 months. N fertilization and HCA influenced the abundance of ammonia oxidizing bacteria and archaea as the key players for nitrification, as well as the abundance of denitrifiers. Soil with spruce sawdust emitted more NO compared to soil with wheat straw, which in relation released more CO, resulting in a comparable overall global warming potential. However, this was counterbalanced by advantages like N immobilization and mitigation of potential NO losses.
像冬小麦这样的植物在播种到下一个生长季节期间氮素吸收不足是众所周知的。特别是在种植了富含氮的作物如油菜或蚕豆之后，土壤中有效氮的保留可能很差，并且硝酸盐（NO）污染水圈以及一氧化二氮（N₂O）污染大气的风险很高。因此，需要新的策略来保存这些未使用的氮资源以供后续农业生产使用。像小麦秸秆这样的高有机碳土壤改良剂（HCA）通过刺激微生物从土壤中吸收氮来促进微生物对氮的固定。为了测试不同HCA对过量氮固定的适用性，我们进行了一项土壤柱实验室培养实验，每个土壤柱含有8千克农业表层A层的砂壤土。我们通过向土壤中添加150千克NH₄-N/公顷来创造一种土壤矿质氮含量高的情景，这些土壤分别以4.5吨碳/公顷的速率添加小麦秸秆、云杉锯末或木质素，或者不添加HCA作为对照。结果表明，小麦秸秆适合以微生物生物量氮的形式快速固定过量氮（高达42千克氮/公顷），其次是锯末。然而，在实验条件下，这种效果在几周后减弱，最终在云杉锯末和小麦秸秆处理中，固定在微生物生物量中的氮分别在8至15千克氮/公顷之间。纯木质素没有刺激微生物对氮的固定。我们还发现，在4个月的时间里，土壤中剩余的秸秆和锯末HCA材料对过量氮的储存（平均24千克氮/公顷）比微生物对氮的固定更为重要。氮肥和HCA影响了作为硝化作用关键参与者的氨氧化细菌和古菌的丰度，以及反硝化细菌的丰度。与含有小麦秸秆的土壤相比，含有云杉锯末的土壤释放出更多的N₂O，而含有小麦秸秆的土壤释放出更多的CO₂，导致总体全球变暖潜力相当。然而，这被诸如氮固定和减轻潜在的N₂O损失等优点所抵消。
