Cover Crops: A California Perspective Z. Kabir, Ph.D. Conservation Agronomist California Nutrient Management Team USDA‐NRCS
Cover Crops: A California Perspective
Z. Kabir, Ph.D.Conservation Agronomist
California Nutrient Management TeamUSDA‐NRCS
Adapted from NASA
Sacramento Valley
Central Valley, Fresno
Practices That Accelerate Soil Erosion
Rain Drops & Soil Erosion
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
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
Planting Cover Crops
Winter Runoff, University of California, Davis
Cover Crop
Fallow
Kabir & Horwath, unpublished
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
Prec
ipita
tion
(mm
)
Perc
ent o
f Rai
nfal
l (%
)
CONVENTIONALLOW INPUTORGANICPrecipitation
Runoff as Percentage of Rainfall, UC Davis
CC
Grower‐Collaborator Field Site
Winter Fallow (NCC) Winter Cover Crop (CC)
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
012345
3AM25 Wed Feb 2004
6AM 9AM 12PM 3PM 6PM 9PM 26 Thu 3AM 6AM 9AM 12PM 3PM
25-26 February 2004
m3smm
2/25/2004 2:00:00 AM - 2/26/2004 4:00:00 PM
Cover Cropped (133.723 m3) Non Cover Cropped (912.445 m3) Precip (52.7 mm)
0.00
0.01
0.02
0.03
0.04
012345
6AM29 Mon Dec 2003
9AM 12PM 3PM 6PM
29 December 2003
m3smm
12/29/2003 3:00:00 AM - 12/29/2003 9:00:00 PM
Cover Cropped (58.015 m3) Non Cover Cropped (246.951 m3) Precip (49.7 mm)
Precip.FallowCover Cropsmm3
/ s
mm
Storm event 1 Storm event 2
Kabir & Horwath
Grower FieldTotal 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
Above and Below Ground
B. Pleasant, 2009Mother Earth News
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
The world above the ground surface and the world below are very tightly linked.
D. Read
Glomalin: Soil Protein
S. Wright, USDA‐ARS
0 10 20 30 40 50 6010
20
30
40
50
60
FallowRyeOatsRye + Oats
Hyphal length = 19.06 + 0.74 (%WSA)
Mycorrhizal hyphal length (m g‐1)
Soil Aggregate Stability
Kabir and Koide, 2002
Corn Early Tassels in Cover Crop Plots
Fallow plots
CC plots
Kabir & Koide, 2000
CC plots
Ear Production of Sweet Corn in Different Cover Crops
Total ears Marketable ears0.0
0.2
0.4
0.6
0.8
1.0
1.2Fallow Oats Rye Oats & Rye
b
a a a
c
bab
a
Cover Crops in Between the Rows
Smith & Kahn
Cover Crops in Vineyard
Chuck Ingels, UCCE
Flowering Cover Crops
Cover Crops in Walnut Orchard
Cover Crops in Walnut Orchard
Cover Crops in Almond Orchard
Almond Picked Up from the Orchard Floor
Cover Crops Mowed to Ground Level
Cover Crops may Serve as Sources of Inoculum for Diseases in Cash Crops
Sclerotinia on vetchVetch
Rust on Cover Crop may Carry Over to Corn
Identify What we Want the Cover Crop to Do?
B. Pleasant, 2009Mother Earth News
• Improve Nutrient availability• Improve soil properties• Reduce soil erosion & improvewater quality
• Suppress weeds, pests and diseases• Provide beneficial habitat• Provide surface mulch
How to Choose a Cover Crop?
B. Pleasant, 2009Mother Earth News
Once we Identify Cover Crop/s We Need
Identify a Planting Windows where the Cover Crop can Fit into Our Crop Rotation
Thank You
Any questions?