5. Annual grain
production
systems are leaky,
especially in high
precipitation
environments.
The 4Rs can
help but
conservation
practices (in-
field and edge-
of-field) are
also needed.
6. Capture
Capture = CC uptake + immobilization by microbes eating high C residues
C
9. In 2016 the OFN
collected 2,172 samples
from 272 tile outlets
across Iowa. Fields w/ CC
had 29% lower nitrate
concentrations than
fields w/o cover crops
and 40% lower total
nitrate loss (lbs/ac/yr).
In 2015, fields w/ CC had
23% lower nitrate
concentrations. field w/cover crops
CCs = cleaner water
fields w/o cover crops
10. Nitrate Leaching in Cover Crops and
Corn/Soybean Systems in Southern Illinois
Rachel Cook, Assistant Professor of Soil Fertility, SIU-Carbondale
Jon Schoonover, Professor of Physical Hydrology, SIU-Carbondale
Karl Williard, Professor of Watershed Management, SIU-Carbondale
Background and Objectives
Nitrogen loss to the environment remains one of the biggest issues facing
agriculture today. Impacts on water quality can be significant and require
immediate attention to develop best management practices to reduce nitrate
leaching and run-off from agricultural fields. One suggested means of
reducing nitrogen losses is through the use of winter cover crops, but there is
very little information on the effect of cover crops on nitrate leaching,
particularly in non-tile drained fields. Additionally, there is little information on
the interaction of tillage and cover crop type (legume or non-legume) on
potential leaching.
11. - Nitrate-N leaching was reduced by cover crop treatments during the late
fall and winter, as the no cover crop plots consistently exhibited the highest
nitrate-N levels
- The highest DRP levels were observed immediately following DAP
application and did not appear to be influenced by cover crop or tillage
treatments
- Shallow soil water nitrate-N levels were highest in the no cover till
treatment in the dormant season, suggesting nitrate-N uptake by cover
crops
- In the paired watershed study, cover crops reduced soil water nitrate-N
levels in all topographic positions following their establishment
Summary of key findings
12. CC and tillage system
effects on concentration
and depth of nitrate-N
15. The negative CC effects on corn
are likely related to nutrient
immobilization and/or root
pathogens
16. Soybean health experiment – multiple locations across IL
Mustard
Rapeseed
Canola
Cereal rye
Cereal rye
November 2010
Soybeans no-till drilled into cereal rye
were the top yielder in 2011
incorporated
pre-plant
no-till
Publication
in press
17. Abstract:
Field trials were conducted from 2010 to 2013 at four locations in Illinois to evaluate
the impact of cover crops (cereal rye (Secale cereale), brown mustard (Brassica
juncea), winter canola (Brassica napus), and winter rapeseed (B. napus) on
soybean (Glycine max) stands and yield, diseases, pathogen populations, and soil
microbial communities. Cover crops were established in the fall each year, and
terminated the following spring either by using an herbicide (no-till farms), by
incorporation (organic farm), or by an herbicide followed by incorporation (research
farm). Although shifts in soilborne pathogen populations, microbial community
structure were not detected, cover crops were found to induce general soil
suppressiveness in some circumstances. Cereal rye and rapeseed improved
soybean stands in plots inoculated with Rhizoctonia solani and decreased
levels of soybean cyst nematode in the soil. Cereal rye increased soil
suppressiveness to R. solani and Fusarium virguliforme, as measured in
greenhouse bioassays. Cereal rye significantly improved yield when
Rhizoctonia root rot was a problem. Using cover crops repeatedly, in the same
field, may achieve more distinct effects on suppressing soybean diseases and build-
up beneficial properties in the soil.
Healthier roots → > nutrient uptake
23. Plant and Soil
August 2001, Volume 235, Issue 2, pp 127-133
Establishment of Bradyrhizobium japonicum for soybean by inoculation of a preceding wheat
crop
R. J. Goos, B. E. Johnson, P. M. Carr
Abstract
On fields with no history of soybean (Glycine max (L.) Merr.) production, inoculation alone is
often inadequate to provide for adequate nodulation the first time this crop is grown. The
objective of this study was to determine if inoculation of spring wheat (Triticum aestivum L.)
seed with Bradyrhizobium japonicum would lead to an increase of B. japonicum numbers in
the soil, and improve nodulation of a subsequent soybean crop. In the greenhouse, wheat
seed inoculation increased B. japonicum numbers from undetectable numbers to greater than
9000/g soil, whereas the numbers of introduced B. japonicum declined in unseeded pots. In
the field, inoculation of wheat seed increased B. japonicum numbers in the soil from
undetectable levels to greater than 4000/g soil the following year. When soybean seed was
inoculated, but grown in soil devoid of B. japonicum, nodules formed only near the point of
seed placement. The heaviest nodulation, and widest distribution of nodules in the topsoil
were found when B. japonicum was established the year before by wheat seed inoculation,
plus soybean seed inoculation. Wheat seed inoculation the year before growing soybean,
combined with proper soybean seed inoculation, should provide for abundant nodulation the
first time soybean is grown on a field.
24.
25. +20 lbs N/a
A little extra N can make a big difference
2x biomass
26.
27.
28.
29.
30.
31. Effect of kill date on typical plant available N (PAN) release from cereal, legume, or mixed
stands. Based on compilation of field data from Willamette Valley cover crop trials. Source:
D. Sullivan
32. Rape
Rye
control
forage rad
oilseed rad
Cover crop treatment
0
30
60
90
120
150
SoiltestP,mg/kg
a
a
c
b
bc
Wye, Fall 2003
Means for 0-45 cm
Third year of cover crop
treatments in a corn-
soybean rotation
Brassicas appear
to be particularly
adept at
solubilizing P Soil Test P
Silt loam at Wye, fall 2003
Means for top 18 inches
Biological
pumping +
organic acid root
exudates
50%
increase
Nutrient cycling: Phosphorus
33. may be large enough to justify extending your rotation
34.
35. Frost seeded
red clover is a more
reliable producer of
biomass and fixer of
N than legume CCs
planted after small
grain harvest
38. Wisconsin data suggest that approximately 70% of
whole-plant N will become available in the first year
following clover, most released before corn begins its
period of rapid uptake.
Good timing!!
39. Wisconsin data suggest that approximately 70% of
whole-plant N will become available in the first year
following clover, most released before corn begins its
period of rapid uptake.
Good timing!!
46. Additional CC species will be spring planted to provide bee forage and
mulch/green manure prior to planting CT and NT pumpkins
Likely species include balansa and berseem clover, phacelia, camelina, mustard…
47. Cereal rye rates ranging from 12 to 120 lbs/a were easily and quickly dialed in
