Managing Cover Crops as a Nutrient Management Tool

Joel Gruver Western Illinois University School of Agriculture

This is impressive - we are doing more with less!!!

Unfortunately the story isn’t all positive

Illinois watersheds are delivering 20% of the N and 11% of the P but only 7% of the water

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.

Capture

Capture = CC uptake + immobilization by microbes eating high C residues

C

http://notillveggies.org/cover-crops-as-management-tools/

Click on boxes for related research by Weil et al.

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

Nitrate Leaching in Cover Crops and Corn/Soybean Systems in Southern Illinois

Rachel Cook, Assistant Professor of Soil Fertility, SIU-CarbondaleJon Schoonover, Professor of Physical Hydrology, SIU-Carbondale

Karl Williard, Professor of Watershed Management, SIU-Carbondale

 Background and ObjectivesNitrogen 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.

- 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

CC and tillage system effects on concentration and depth of nitrate-N

When commodity prices are low,

IA Soybean Association’s On-Farm Network® Replicated Strip Trial Database

The negative CC effects on corn are likely related to nutrient immobilization and/or root

pathogens

Soybean health experiment – multiple locations across IL

MustardRapeseed

CanolaCereal ryeCereal rye

November 2010

Soybeans no-till drilled into cereal rye were the top yielder in 2011

incorporatedpre-plant

no-till

Publication in press

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

Early planting trade-offs – Risk vs. Rooting depth

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.

+20 lbs N/a

A little extra N can make a big difference

2x biomass

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

Cover crop treatment

0

30

60

90

120

150

Soi

l te s

t P, m

g/kg

a a

c

bbc

Wye, Fall 2003Means 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 PSilt loam at Wye, fall 2003Means for top 18 inches

Biological pumping + organic acid root exudates

50% increase

Nutrient cycling: Phosphorus

may be large enough to justify extending your rotation

Frost seeded red clover is a more reliable producer of biomass and fixer of N than legume CCs planted after small

grain harvest

Frost seeded red clover is

more weather resilient

More than most

legumes

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!!

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!!

Multispecies CC mixesare much more of an option after small grains

http://www.greencoverseed.com/

This is a very useful tool for planning CC mixes!

Excellent nutrient scavenger Excellent N fixer

Oilseed sunflower Sunn hemp

Must be planted by planted by ~8/15 in

the central Corn Belt

11/6/2016 at the WIU Organic Research Farm

Sizing residues, increasing soil contact and planting a very low rate of cereal rye (12 lbs/a)

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…

Cereal rye rates ranging from 12 to 120 lbs/a were easily and quickly dialed in

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