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

• Applicant: Professor Dr. Ulrich Köpke
• Subject Area: Plant Cultivation, Plant Nutrition, Agricultural Technology ; Soil Sciences
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259988109

• Final Report Year: 2018

Final Report Abstract

The research summarized in this final report focused on i. monitoring the persistence of effects on soil structure and the performance of subsequent crops generated by fodder cropping and ii. characterizing biopores influenced by roots or earthworms with respect to nutrient contents. With respect to biopore genesis, it was confirmed that taprooted precrops and not earthworms were the main agents of biopore formation at the site under study. The percentage increase in biopore density after growing chicory vs fescue for two years was 20 %. This effects persisted at least for seven years. A second period of foddercropping did not result in further increase in biopore density, but increased density of coarse and blocked biopores indicate an influence of earthworms on biopore quality: Biopores colonized by earthworms for a period of six months had higher contents of nitrogen and plant available P than biopores influenced by roots. Crops did show preferential root growth in biopores with 5-30% roots in biopores depending on crop, year and soil depth, but winter wheat did not prefer N rich biopores compared with biopores having a lower N content. Allorhizous crops had a higher share of root-length density in biopores than homorhizous crops. Over a period of seven years with different climatic conditions, grain yield and partially also root and shoot growth during the vegetation period was analyzed for seven spring crops and eight winter crops. The overall evaluation showed that in most years, accessibility of the subsoil in early growth stages was improved by chicory as a precrop, while especially in later growth stages RLD in the topsoil and upper subsoil was higher after fescue. Specific root length was also higher after fescue. Only in the year with the most abundant rainfall in May root growth of winter barley was not different after the two precrops. Shoot biomass and grain yield were not affected by the precrops except for spring barley without nitrogen fertilization in the year with the driest winter followed by a dry spring, when grain yield was increased after chicory, via higher RLD in the subsoil until anthesis. In the same year, grain N and P uptake of winter oilseed rape was significantly higher after fescue, probably via higher RLD in the topsoil and abundant rainfall in July. Further studies on soils with lower water holding capacity will show if increasing biopore density via growing taprooted perennial foddercrops can be a strategy to increase yield stability. Artificially removing precipitation by rain shelters did only affect topsoil water contents and did not reduce grain yield in three years. However, in the first year spring oilseed rape after chicory had a much higher ratio of shoot biomass to root length. Whether this increase in efficiency was realized via higher root diameter resulting in decreased root respiration and increased root longevity has to be clarified in further studies.

Publications

• Optimising Cropping Techniques for Nutrient and Environmental Management in Organic Agriculture. Sustainable Agriculture Research, Vol. 4. 2015, No. 3, pp. 15-25.
  Köpke U., Athmann M., Han E., Kautz T.
  
• Quantification of soil biopore density after perennial fodder cropping. Plant and Soil, Vol. 394. 2015, Issue 1–2, pp. 73–85.
  Han E., Kautz T., Perkons U., Lüsebrink M., Pude R., Köpke U.
  
• Research on subsoil biopores and their functions in organically managed soils: a review. Renewable Agriculture and Food Systems, Vol. 30. 2015, Issue 4, pp. 318-327.
  Kautz T.
  
• Root growth dynamics inside and outside of soil biopores as affected by crop sequence determined with the profile wall method. Biology and Fertility of Soils, Vol. 51. 2015, Issue 7, pp. 847–856.
  Han E., Kautz T., Perkons U., Uteau D., Peth S., Huang N., Horn R., Köpke U.
  
• Precrop root system determines root diameter of subsequent crop. Biology and Fertility of Soils, Vol. 52. 2016, Issue 1, pp. 113–118.
  Han E., Kautz T., Köpke U.
  
• Dynamics of plant nutrient uptake as affected by biopore-associated root growth in arable subsoil. Plant and Soil, Vol. 415. 2017, Issue 1–2, pp. 145–160.
  Han E., Kautz T., Huang N., Köpke U.
  
• Six months of L. terrestris L. activity in root-formed biopores increases nutrient availability, microbial biomass and enzyme activity. Applied Soil Ecology, Vol. 120. 2017, pp. 135-142.
  Athmann M., Kautz T., Banfield C., Bauke S., Hoang D. T. T., Lüsebrink M., Pausch J., Amelung W., Kuzyakov Y., Köpke U.