Biopores in the subsoil: Formation, nutrient turnover and implications for root growth of field crops

在初步研究中，我们的工作组已经表明，在用主根系统种植饲料作物后，底土中大尺寸生物孔隙的密度在相当短的时间内增加。无生态蚯蚓并没有对初级生物矿的产生做出那么大的贡献，尽管它们的丰度因土壤休息和作物残留而增加。稳定生物孔隙并影响其孔壁特征是在有利的生境条件下可能在短期内发生的生物活性的潜在影响;然而，这一假设需要进一步研究。C和N含量的个别生物孔隙变化很大，大概是作为一个后果的孔隙成因和殖民历史。大田作物的根经常定殖于生物孔并与生物孔壁建立接触，而不管根结构如何。然而，需要更多的研究如何生物孔特性影响根系生长的问题。我们的新提案旨在量化作物序列与饲料作物对生物孔特性和后续作物性能的影响。为此，我们将使用以前建立的实地实验，包括土壤温度和湿度的监测系统。继续调查将有助于了解饲料种植产生的持久影响。监测三个具有类似设计但在2007年至2012年期间建立的系列田间试验，可以考虑不同年份和不同天气条件的影响。此外，我们的目标是量化的降水，养分浓度在表土和生物孔系统的养分收购从子地块与雨水庇护和表土交换底土的相互作用。此外，我们将量化已知历史的生物孔壁的性质（蚯蚓定植与根定植）和生物活性对孔壁性质的影响。从单个生物孔中收获根和孔壁材料结合原位内窥镜将提供关于具有不同孔壁性质的生物孔对作物根的吸引力的新见解。我们希望我们的研究能够提供新的见解，了解具有主根和生物活性的作物的种植如何影响生物孔密度和孔壁特性，以及哪些特性有利于作物根利用生物孔作为伸长途径和营养获取热点。

In preliminary studies our working group has shown that after growing fodder crops with taproot systems the density of large sized biopores in the subsoil increased within quite a short period of time. Anecic earthworms did not contribute to primary biopore generation that much, although their abundance was increased by soil rest and crop residues. Stabilizing biopores and influencing their pore wall characteristics are potential effects of earthworm activity that under favorable habitat conditions may take place in the short-term; however this assumption needs further investigation. C and N contents of individual biopores vary largely, presumably as a consequence of the pores genesis and colonization history. Roots of field crops frequently colonize biopores and establish contact with the biopore wall, regardless of the root architecture. However, more research is needed on the question how biopore properties influence root growth. Our new proposal aims to quantify the effects of crop sequences with fodder crops on biopore properties and the performance of subsequent crops. For this purpose we will use previously established field experiments, including the monitoring systems for soil temperature and moisture. Continued investigation will allow understanding the lasting effects generated by fodder cropping. Monitoring three field trials with similar design but established in a series from 2007 to 2012 enables taking into account the effect of different years with different weather conditions. In addition, we aim to quantify the interactions of precipitation, nutrient concentration in the topsoil and biopore systems for nutrient acquisition from the subsoil in subplots with rain shelter and topsoil exchange. Furthermore, we will quantify the properties of walls of biopores with known history (colonization by earthworms vs. colonization by roots) and the effect of earthworm activity on pore wall properties. Harvesting roots and pore wall material from individual biopores combined with in situ-endoscopy will provide new insights about the attractiveness of biopores with different pore wall properties for crop roots. We expect our research to give new insights on how cultivation of crops with taproots and earthworm activity affect biopore density and pore wall properties and which properties are beneficial for allowing crop roots to use biopores as pathways for elongation and hot spots for nutrient acquisition.