69th SWCS International Annual Conference “Making Waves in Conservation: Our Life on Land and Its Impact on Water” July 27-30, 2014 Lombard, IL

1. Cover Crops: A California Perspective
Z. Kabir, Ph.D.
Conservation Agronomist
California Nutrient Management Team
USDA‐NRCS

2. Adapted from NASA

3. Sacramento Valley

4. Central Valley, Fresno

5. Practices That Accelerate Soil Erosion

6. Rain Drops & Soil Erosion

7. When Raindrops Impact Bare Soil
Raindrop splash pattern from a slope landscape,
(Envr. Soil Physics, Hillel, 2005)
Dislodging soil particles and splashing them 3 to 7 ft away

8. Soil Erosion
Sheet: is the uniform removal of
a thin film of soil from the land
surface
O’Geen, UC Davis
When sheet flows begin to
concentrate on the surface, rill
erosion occurs
Gully: as duration and/or intensity
of rain increases and runoff
volumes accelerate - create
incised channels
Splash Sheet Rill Gully Channel erosion

9. Planting Cover Crops

10. Winter Runoff, University of California, Davis
Cover Crop
Fallow
Kabir & Horwath, unpublished

11. 0
10
20
30
40
50
60
0
20
40
60
80
100
1-17
1-24
1-25
1-31
2-5
2-11
2-13
2-14
2-26
3-9
Precipitation(mm)
PercentofRainfall(%)
CONVENTIONAL
LOW INPUT
ORGANIC
Precipitation
Runoff as Percentage of Rainfall, UC Davis
CC

12. Grower‐Collaborator Field Site
Winter Fallow (NCC) Winter Cover Crop (CC)

13. Discharge Hydrograph Comparing Growers’ Fields
Early Storm Season
(December 29th, 2003)
Late Storm Season
(February 25th, 2004)
0.00
0.01
0.02
0.03
0.04
0
1
2
3
4
5
3AM
25WedFeb2004
6AM 9AM 12PM 3PM 6PM 9PM 26Thu 3AM 6AM 9AM 12PM 3PM
25-26February2004
m3smm
2/25/20042:00:00AM-2/26/20044:00:00PM
CoverCropped(133.723m3) NonCoverCropped(912.445m3) Precip(52.7mm)
0.00
0.01
0.02
0.03
0.04
0
1
2
3
4
5
6AM
29MonDec2003
9AM 12PM 3PM 6PM
29December2003
m3smm
12/29/20033:00:00AM-12/29/20039:00:00PM
CoverCropped(58.015m3) NonCoverCropped(246.951m3) Precip(49.7mm)
Precip.FallowCover Crops
m
m
3
/
s
m
m
Storm event 1 Storm event 2
Kabir & Horwath

14. Grower Field
Total Winter Discharge Comparisons, UC Davis
16.3%
0.52 m/s
0.9%
Rainfall Discharged as Runoff
Average Peak Runoff Velocity
Fallow (NCC) Cover Crops
0.24 m/s

16. Above and Below Ground
B. Pleasant, 2009
Mother Earth News

17. Cover Crops Roots attract Microbes
Bacteria and fungi are like little fertilizer bags
Exudates: carbohydrates and proteins secreted by roots;
attract bacteria, fungi, nematodes, protozoa
Nematodes and protozoa eat exudates and excrete fertilizer

18. The world above the ground surface and the world
below are very tightly linked.
D. Read

19. Glomalin: Soil Protein
S. Wright, USDA‐ARS

20. 0 10 20 30 40 50 60
10
20
30
40
50
60
Fallow
Rye
Oats
Rye + Oats
Hyphal length = 19.06 + 0.74 (%WSA)
Mycorrhizal hyphal length (m g‐1)
Soil Aggregate Stability
Kabir and Koide, 2002

21. Corn Early Tassels in Cover Crop Plots
Fallow plots
CC plots
Kabir & Koide, 2000
CC plots

22. Ear Production of Sweet Corn in Different Cover Crops
Total ears Marketable ears
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Fallow
Oats
Rye
Oats & Rye
b
a a a
c
b
ab
a

23. Cover Crops in Between the Rows
Smith & Kahn

25. Cover Crops in Vineyard
Chuck Ingels, UCCE

26. Flowering Cover Crops

27. Cover Crops in Walnut Orchard

28. Cover Crops in Walnut Orchard

29. Cover Crops in Almond Orchard

30. Almond Picked Up from the Orchard Floor

31. Cover Crops Mowed to Ground Level

32. Cover Crops may Serve as Sources of Inoculum for
Diseases in Cash Crops
Sclerotinia on vetchVetch

33. Rust on Cover Crop may Carry Over to Corn

34. Identify What we Want the Cover
Crop to Do?
B. Pleasant, 2009
Mother Earth News
• Improve Nutrient availability
• Improve soil properties
• Reduce soil erosion & improve
water quality
• Suppress weeds, pests and diseases
• Provide beneficial habitat
• Provide surface mulch

35. How to Choose a Cover Crop?
B. Pleasant, 2009
Mother Earth News
Once we Identify Cover Crop/s We Need
Identify a Planting Windows where the
Cover Crop can Fit into Our Crop Rotation

36. Thank You
Any questions?