COST 832

Text of presentation given by Ralph Meissner and Detlev Deumlich, Working Group 2 members from Germany, on 15 July 1998.

1. Leaching and sub-surface runoff

Important pathways:

• Piston flow (vertical displacement of water)
• Deep drainage to groundwater
• Bypass flow (rapid macropore transfer)
• Interflow /lateral flow
• shallow subsurface flow
• throughflow (deep downslope lateral flow)

Because of using different definitions and analytical methods the comparison of P investigations is very difficult. One of the most important targets should be the comparability of measured data.

In the water management authorities of Germany the following parameters are relevant:

TP - total P (unfiltrated, using K₂S₂O₈ as oxidation solvent)

TDP - total dissolved P (filtrated- mash 45 µm and using K₂S₂O₈ as oxidation solvent)

SRP (soluble reactive P - in Germany usually: ortho -P)

BERGSMA, E. (Ed.) (1996)

Intern. Soc. for Soil Science

Intern. Inst. for Aerospace Survey and Earth Sciences

Intern. Soil Reference and Information Centre

ISBN 90-71556-15-8)

Page 165- 239 Definitions and descriptive aspects of terms:

• Enrichment ratio: the ratio of the concentration of a plant nutrient element in eroded soil material to that in the soil before erosion
• Erodibility: the influence of the soil profile, distinct from that of relief, on the rain erosion process, determined by the availability of material for erosion and the generation of overland flow volume from rain
• Infiltration rate: a soil characteristic describing the maximum rate at which water can enter the soil under specified conditions, including the presence of an excess of water
• Rain erosivity: potential ability of rain to cause erosion due to its kinetic energy and volume
• Rainfall interception: the interception an temporary holding of precipitation by vegetation or other materials
• Rainfall simulation: the controlled application of water drops or artificial rain to experimental plots using some type of drop former
• Rainfall energy = rain energy = kinetic energy of rainfall: the energy contained in falling drops of rain, expressed in units of kinetic energy, per unit volume of rainfall
• Runoff plot: an area of land, usually small, arranged so that the portion of rainfall or other precipitation flowing off, and perhaps carrying soluble materials and soil, may be measured, usually the flow from runoff plots includes only surface runoff; the reference plots for the USLE are 22 meters long and 2 meters wide, on a 9 % slope; measures are possible by natural and artificial rainfall
• Sediment delivery ration: a measure of the sediment actually reaching a stream or lake expressed as the quantity of material reaching a specific point in a drainage system divided by the quantity actually eroded in the catchment above the same point
• Seepage: the slow movement of gravitational water through the soil; subsurface water emerging at the land surface from lateral throughflow

Also, the Glossary of Soil Science Terms 1996; SSSA, Madison WI can be used.

Methodology of measuring:

• Measurement plots and small catchments, sediment samplers (field measurement boxes)
• Suspension samples in greater containers with integrated smaller boxes (bucket or bottles)
• Time dependent samples of overland flow within a rainstorm event (divided by Coshocton wheels or other enrichments
• Texture of eroded materials after drying
• Soluble nutrient content in water in sampled bottles (total P with Flow solution with Ascorbic-acid-method manufactured by SKALAR)
• Articulated nutrients by drying (up to date plant available P only) (EPOS - manufactured by EPPENDORF)

3. Sampling methods

 For leachates: lysimeter method- continuously sampling the seepage water

• precise estimation of water balance
• concentration and loads for different matters

• no in situ measurement
• expensive costs for installation

Tension cup method: discontinuously sampling of seepage water (free drainage water)

• in situ measurement
• permanent measurement in different soil depth

• non sufficient estimation of water balance, concentration and loads

Drainage pipe method: no experience at this time (problem: estimation of the catchment area!)

Soil cores: not relevant for estimation of P leaching in Germany. Mostly used for estimation of P (plant available content or total P content in soils) in the frame of recommendations for fertilization.