Biopores in the subsoil: Formation, nutrient turnover and effects on crops with distinct rooting systems (BioFoNT)

多年生饲料种植可能通过形成广泛的根系和暂时的土壤休息来增加地下生物孔密度。我们将量化紫花苜蓿（Medicago sativa）、菊苣（chichorium intybus）和黄羊茅（Festuca arundinacea）在应用研究单元中央田间试验（CeFiT）中分别生长1年、2年和3年后的根长密度、蚯蚓丰度和生物孔大小等级。拍摄参数包括蒸腾，气体交换和叶绿素荧光将经常记录。在作物产量、养分转移和h2释放方面，将对油菜和谷物的作物前效应进行量化。与散装土壤相比，与生物孔相关的土壤（即钻探层）通常富含养分，因此被认为是养分获取的潜在热点。然而，据报道，根与孔壁之间的接触面积很小。目前尚不清楚钻探圈中存在的营养物质在多大程度上被利用，以及底土生物孔对作物的营养供应可能具有哪些潜在的相关性。我们将使用一个灵活的视频镜来确定生物孔中根与土壤的接触。利用15N作为示踪剂，对蚯蚓向地下圈输入的氮以及随后不同生根系统作物（油菜与谷物）从地下圈可能再吸收的氮进行量化。

Perennial fodder cropping potentially increases subsoil biopore density by formation of extensive root systems and temporary soil rest. We will quantify root length density, earthworm abundance and biopore size classes after Medicago sativa, Cichorium intybus and Festuca arundinacea grown for 1, 2 and 3 years respectively in the applied research unit’s Central Field Trial (CeFiT) which is established and maintained by our working group. Shoot parameters including transpiration, gas exchange and chlorophyll fluorescence will frequently be recorded. Precrop effects on oilseed rape and cereals will be quantified with regard to crop yield, nutrient transfer and H2-release. The soil associated with biopores (i.e. the driloshpere) is generally rich in nutrients as compared to the bulk soil and is therefore supposed to be a potential hot spot for nutrient acquisition. However, contact areas between roots and the pore wall have been reported to be low. It is still unclear to which extent the nutrients present in the drilosphere are used and which potential relevance subsoil biopores may have for the nutrient supply of crops. We will use a flexible videoscope to determine the root-soil contact in biopores. Nitrogen input into the drilosphere by earthworms and potential re-uptake of nitrogen from the drilosphere by subsequent crops with different rooting systems (oilseed rape vs. cereals) will be quantified using 15N as a tracer.