Nährstoffakquisition aus dem Unterboden: N-Aufnahme in Bioporen
Bodenwissenschaften
Zusammenfassung der Projektergebnisse
The aim of the research summarized in this final report was to quantify N uptake by spring barley from the subsoil in total and from subsoil biopores, linking N uptake analyses to monitoring root growth in and around biopores throughout the cultivation period with in situ endoscopy. This objective was approached by producing soil columns (subsoil section: 10 cm radius, 40 cm length) with either a 15N-labelled topsoil section labelled via decomposing labelled lucerne in topsoil (for quantification of N uptake from the subsoil in total) or with a central macropore with 15N-labelled drilosphere, produced via feeding anecic earthworms with labelled lucerne litter (for quantification of N uptake from subsoil biopores). With respect to quantifying N uptake from the subsoil drilosphere, important advances were made: With focusing on just one central macropore per column and with a comparatively short time of earthworm incubation it was possible to label only the drilosphere, i.e. only one pool in the subsoil column. Microbial intake to the bulk soil from the lucerne fed to earthworms and lateral transfer of the label around the drilosphere were minimized. N uptake from macropore walls could be calculated and amounted to 6.5% after 46 days of crop growth and to 25.7% after 89 days of crop growth. This implies that earthworm cast is an appreciable source of N derived from the subsoil. Monitoring root growth in biopores during cultivation revealed that root-soil contact, share of roots with root hairs and share of active roots increased with soil depth – however, as measured from columns where only one subsoil segment of 10 cm height was labelled, it became evident that during the period of 46 days of crop growth N was only taken up in 0-20 cm soil depth, even though roots had explored the full 40 cm of the pore. This may, however, change in later development stages. Therefore, this experimental approach should be repeated with longer cropping duration. N uptake from the subsoil in total could not be quantified, presumably because lucerne decomposition resulted in heterogenous labelling of the topsoil and crops may have taken up N from one pool preferentially. Future studies should quantify 15N-enrichment in different grain size fractions and measure depletion of the different pools by crops. Likewise, 15N-enrichment in different grain size fractions of earthworm cast should be measured. The methodology developed in WP 2 and WP 3 is now apt for quantifying N uptake from biopores in pot experiments, and linking this uptake to root growth in biopores. On the long run, the methodology should be transferred to the field.
Projektbezogene Publikationen (Auswahl)
- (2017): Six months of L. terrestris L. activity in root-formed biopores increases nutrient availability, microbial biomass and enzyme activity. Appl Soil Ecol 120: 135-142
Athmann M, Kautz T, Banfield C, Bauke S, Hoang D T T, Lüsebrink M, Pausch J, Amelung W, Kuzyakov Y, Köpke U
(Siehe online unter https://doi.org/10.1016/j.apsoil.2017.08.015) - (2018) Effects of Continuous Vertical Soil Pores on Root and Shoot Growth of Winter Wheat: A Microcosm Study. Agricultural Sciences 9: 750-764
Dresemann T, Athmann M, Heringer L, Kautz T
(Siehe online unter https://dx.doi.org/10.4236/as.2018.96053) - (2019): Comparing macropore exploration by faba bean, wheat, barley, and oilseed rape roots using in situ endoscopy. Journal of Soil Science and Plant Nutrition
Athmann M, Sondermann J, Kautz T, Köpke U
(Siehe online unter https://doi.org/10.1007/s42729-019-00069-0) - (2019): Modeling the impact of biopores on root growth and root water uptake. Vadose Zone Journal 18 (1)
Landl M, Schnepf A, Uteau D, Peth S, Athmann M, Kautz T, Perkons U, Vereecken H, Vanderborght J
(Siehe online unter https://doi.org/10.2136/vzj2018.11.0196)
