Forage cover crops: impacts on nutrition, soil, and ecosystem services

Jillian Bainard & Luke BainardSwift Current Research and Development Centre

Forage Cover Crops: What are they?• Cover crops are grown to

improve ecosystem and soil health; often ploughed down

• Using annual forages, these crops can be grazed or harvested for feed

• Many perceived benefits:• Improved soil/water relations• Improved soil fertility • Pest management• Etc.

• Forage Polycultures (Funded by the Agriculture Development Fund (ADF): Schellenberg, Lamb, Ren)

• Winter Polycultures (Funded by ADF: Schellenberg, LaForge)

• Cover Crop spacing for weed control (Funded by ADF: Lamb, Schellenberg)

• Swath grazing forage polycrops (ADF: Lardner & Iwaasa)

• Nitrogen and residue management of forage polycultures (Saskatchewan Cattlemen’s Association (SCA) and SWFA: Bainard, et al.)

• Soil microbial ecology in forage cover crops (Funded by the Manitoba Beef and Forage Initiative (MBFI): Luke Bainard)

Forage Cover Crops: Previous and ongoing research

MBFI Project Design• Sites: Brookdale Research Farm (near Brandon MB)

South Farm, SCRDC (Swift Current SK)

• Four cropping treatments: 1, 3, 6, 9 species(Oats, peas, Graza forage radish, Italian Ryegrass, hairy vetch, Winfred brassica, sorghum, crimson clover, Hunter brassica)

• Half of each Brookdale plot was grazed in October 2016

• Conditions: 2016 very wet (delayed seeding in Brookdale), 2017 very dry

Swift Current 2016 Swift Current 2017

Biomass Productivity: Swift Current• By the end of the growing season, productivity of mixtures was similar to

the oat monoculture

July August

kg/h

a

kg/h

a

July August

kg/h

a

July AugustJuly August

kg/h

a

Brookdale 2016 Brookdale 2017

Biomass Productivity: Brookdale• Oat monoculture consistently produced more biomass than the mixtures • Grazing did not affect the productivity of the following year

no effect

no effect

no effect

no effect

Cu

Fe

TKN

TP

TK

ADF

NDF

Ca

no effect

Forage Nutrition

MIXTURES• Mixtures had a significant effect on various aspects of forage nutrition (compared to the oat monoculture)

• Grazing had a minimal effect on the nutrition of the crop the following year

GRAZING

Protein NDF

July August July August

Forage Nutrition• Mixtures had higher protein (TKN) and lower fibre (NDF)• Swift Current shown (similar in Brookdale)

MIXTURES GRAZING

no effect

Total N

NO3-N

PO4-P

SO4-S

Enzyme activity

Organic C no effect

no effectno effect

no effect

no effectno effect

no effect

no effectno effect

Soil Chemical Properties• Mixtures had a

minimal effect on soil chemical properties

• Grazing had no significant effect on soil chemistry the following year

MIXTURES GRAZING

Bacteriadiversitycomposition

no effect

Fungidiversitycompositionpathotrophssymbiotrophssaprotrophs

no effect no effect

no effect

(one site)

no effect

no effect

no effect

no effect

no effect

shift shift

Soil Microbial Communities• Fungal community

composition was different under mixtures than monoculture

• Grazed plots had lower bacterial diversity and higher fungal diversity the following year

significance?

• Productivity: Depending on the location, the productivity of the mixtures used in this study were equal to or slightly less than the oat monoculture

• Nutrition: forage nutrition value was higher in the mixtures (lower fibre and higher protein)

SUMMARY

• Mixtures responded similarly to the oat monoculture under stressful conditions (drought and nutrients)

• Soil chemical properties: no clear short term benefits, but this may be more evident over longer time frames

SUMMARY

• Soil biological communities: early indications show that the fungal community is impacted by mixtures and by grazing

SUMMARY• Don’t forget:

• Species selection is important, seeding rate and date is important • Caution when grazing brassicas

• New work: • Fertility and residue management• More grazing trials

Thank you! Questions?

Acknowledgements:

• AAFC staff and students• MBFI staff