The document describes a field trial studying the effects of drainage system renewal on nutrient leaching and crop yield. The trial tested different drainage spacings and trench designs. Precipitation and subsurface runoff were measured, as well as total phosphorus and nitrogen loads in runoff water. Improved drainage led to lower total phosphorus loads but higher total nitrogen loads and higher crop yields compared to the old drainage system. While climate-adapted water management measures show benefits, challenges remain around legislation, costs, knowledge gaps, and ensuring adequate water supply.

2. Effects of drainage system
renewal on nutrient leaching and
crop yield
Ingrid Wesström, SLU, Department of soil and environment
Ingrid.Wesstrom@slu.se
Abraham Joel, SLU, Department of soil and environment
Petter Ström, Väderstad AB

3. A changing climate – impact on runoff
from drainage systems
Östergötland
Halland
Wesström & Joel, 2018
Month Month

4. On going field trial
Treatments
Treatments
• (A) old tile system, 10 m drain
spacing
• (B) plastic pipe, 10 m drain spacing
• (C) plastic pipe, 5 m drain spacing
• (D) plastic pipe, 10 m drain spacing
and lime incorporated in trench
backfill
Photo: Bob Wennström

5. Experimental setup Experimental setup
• Protection drains (green)
• Elevation (black)
• Elevation trench (red)
• Drain depth (m) (red)
Photo: Petter Ström

6. Site description
• Sala, central Sweden (59o48’26’’N
16o47’09’’E)
• Conventionally cultivated clay soil
with high organic matter content in
the top soil
• Reduced soil tillage system
• P-AL class IVA (P-AL number 8.2).
• Field trial established in 2018
• Measurements started in 2019

7. Measurements
• From each individual plot, water
flow is measured with 2-sided
tipping buckets
• A data logger records runoff per
hour and controls extraction of
flow-proportional water samples
• Aggregate water samples are
collected every 14 days
• Analyses of phosphorus and
nitrogen content in water
samples
• Dry matter yield and grain quality
are assessed at plot level
Photo: Petter Ström

8. Precipitation during the experimental years
July 2019-June 2020 and July 2020-June 2021
0
20
40
60
80
100
120
July Aug Sept Oct Nov Dec Jan Feb March April May June
Precipitation
(mm)
Month
2019/20
2020/21
Long-term mean (1961-1990)
Long-term mean precipitation data (1961-1990) are from
SMHI’s meteorological station in Sala

9. Cumulative subsurface runoff (mm) during the
periods November 2019 to June 2020 and July
2020 to June 2021

10. Cumulative total phosphorus loads in
subsurface runoff, years 2019/20 and 2020/21

11. Cumulative nitrogen loads in subsurface
runoff, years 2019/20 and 2020/21

12. Yield years 2020 and 2021
Treatment
Year 2020
Winter wheat
Yield w c 15%
(kg ha-1)
Relative
total yield
Treatment
Year 2021
Canola
Yield DM
(kg ha-1)
Relative
total yield
A 8 750 100 A 2 430 100
B 9 810 112 B 2 536 104
C 9 710 111 C 2 501 103
D 10 496 120 D 2 796 114
Average 9 691 Average 2 559

13. Conclusion from field trial so far
Effects of improved drainage on runoff
• No major increase in infiltration
• No major increase in subsurface runoff
Effects of improved drainage on P and N leaching
• Lower Tot-P loads
• Higher Tot-N loads
• + Higher yields

14. Climate adapted water management
measures have some obstacles
• Legislation
• Investment costs
• Water supply
• Knowledge gaps

15. Tack
för
er
uppmärksamhet!

16. Summary of results
Treatment Precipitation
(mm)
Subsurface
drainage (mm
ha-1)
Total
phosphorus
load (kg ha-1)
Total nitrogen
load (kg ha-1)
Year 2019/2
020
2020/2
021
2019/2
020
2020/2
021
2019/2
020
2020/2
021
2019/2
020
2020/2
021
A 628 538 138 184 0.54 0.25 10.6 19.2
B 628 538 139 183 0.31 0.12 15.2 25.4
C 628 538 128 168 0.18 0.11 15.7 24.8
D 628 538 137 196 0.10 0.08 16.6 27.4