Pesticides Research, 63. – Scenarios and Model Describing Fate and Transport of Pesticides in Surface Water for Danish Conditions – Appendix A - Description of Soil Types in the Test Catchments at the Time of Selection

Scenarios and Model Describing Fate and Transport of Pesticides in Surface Water for Danish Conditions

Appendix A

1 Description of Soil Types in the Test Catchments at the Time of Selection.

The soils under agriculture in the two catchments may be classified as shown in :

Table 1.1 Distribution of soil types in Lillebæk and Odder Bæk catchments

	jb.no. FK	1 1	2 2	3-4 3	5-6 4	7 5	8-10 6	11 7	Total
Odder Bæk	in ha in %	804 72	187 17	73 7				55 5	1119 101
Lillebæk	in ha in %			17 4	404 96				421 100

The Danish soil classification ranks the soil according to , which also includes the soil type distribution of the country.

Table 1.2 Soil classification and distribution of soil types in Denmark (Landbrugets rådgivningscenter, 1997)

Texture definition for soil type	jb-no.	Weight percent
		Clay > 2 µm	Silt 2-202 µm	Fine sand 20-2002 µm	Sand, total 20-2000 µm	Humus 58,7% C	% of cropped area in DK
Coarse sandy soil Fine sandy soil	1 2	0-5	0-20	0-50 50-100	75-100		24 10
Coarse clay-mixed sand Fine clay-mixed sand	3 4	5-10	0-25	0-40 40-95	65-95	Under 10	7 21
Coarse sand-mixed clay Fine sand-mixed clay	5 6	10-15	0-30	0-40 40-90	55-90		4 20
Clay	7	15-25	0-35		40-85		6
Heavy clay	8	25-45	0-45		10-75		1
Very Heavy clay	9	45-100	0-50		0-55
Silt	10	0-50	20-100		0-80
Humus	11					Over 10	7
Special soil type	12

Soil type 1, which is strongly represented in Odder Bæk, covers 24% of Denmark. Soil type 2 covers 10% of Denmark and 17% of Odder Bæk catchment. Soil type 3 and 4 covers 28% of Denmark and only 7 and 4% of the two catchments. Soil type 5 and 6 covers 24% of Denmark and 96% of Lillebæk. The catchments may thus be said to cover soil conditions in around 58% of the country. The group of clay-mixed sands, covering 28% of the country is under-represented.

The soil types present in the test catchments should be used also for the scenarios. This is in line with the choice of the catchments as representative, and it is unlikely that we can find two other catchments representing more of the country than these two areas. The soil description also covers the presence of macropores and organic matter content. However, organic matter content could be one of the parameters to be chosen for inclusion in the Monte Carlo simulations in the final registration tool.

Issues Related to Soil Erosion

The choice of catchments may, however, not be fully representative when it comes to transport pathways. The selected soil types will be risk areas in view of the quick flow through the coarse sand and the macropores, but not with respect to surface flow and erosion. The surface water flow and the soil erosion will be linked to topography, but steep slopes are not the dominating factor in erosion in Denmark. It appears that local saturation is a more important factor, so places where a plough sole or another limiting horizon is present are prone to erosion. It is thus likely that erosion may be of less importance in the chosen catchments than in the under-represented soils containing much fine sand. Studies in Foulum on this soil type have shown significant erosion on these soils. This soil type dominates none of the monitoring catchments. If you remember the figures from the first day, Foulum lost about ten times as much pesticide via soil erosion as Ødum.

It is difficult to foresee whether this soil type will give rise to more or less pesticide in the river than the other scenarios. For soluble pesticides, probably less than the coarse sandy scenario, because the pesticide will move into the profile, but not as fast as in case of coarse sand. The effects of erosion will, however, be visible in case of strongly adsorbing pesticides.

In principle, there ought to be a scenario representing the 28% of our soils. In reality, we do not seem to have the data to establish it at the moment. It is probably possible to generate erosion parameters and hydraulic parameters based on the Foulum soils, but we have no validation possibilities, even if we were able to select a catchment and assumed the Foulum parameters for the soil.

References

Blicher-Mathiesen, G., Grant, R., Jensen, C., and Nielsen, H. (1990): Landovervågningsoplande. Vandmiljøplanens Overvågningsprogram 1989. Faglig rapport fra DMU, nr. 6 (Hovedrapport). Danmarks Miljøundersøgelser, September 1990.

Landbrugets Rådgivningscenter (1997); Håndbog for Plantedyrkning. Landbrugets Rådgivningscenter.