Soil quality and cover crops in red raspberry in the Pacific Northwest

Rachel Rudolph, Inga Zasada, and Lisa DeVetter

Small Fruit ConferenceDecember 1, 2016

Introduction

• Red raspberry is a valuable crop to Washington

• Total acreage has increased in the Pacific Northwest (PNW), but crop longevity has decreased

• The decline is attributed to various factorshttp://www.raspberries.us/

Soil management challenges

• Pathogenic fungi• Pathogenic bacteria• Plant parasitic nematodes• Improper pH• Soil nutrient deficiency

Soil management challengesPratylenchus penetrans, or root lesion nematode (RLN), is one of the most important raspberry pests

• Non-segmented roundworm • Migratory endoparasite • Feeds on roots, causes reduced

uptake of water and nutrients• Dark lesions develop on roots• Plants can decline rapidly

http://extension.oregonstate.edu/umatilla/pests/rootlesionnematodes

Current management practices• Alleyways are commonly kept clean by repeated

rototilling/cultivation and herbicides• Alleyway cover cropping is not a common practice

in PNW red raspberry systems• Repeated cultivation can:

• Increase soil erosion • Increase compaction • Contribute to loss of soil physical structure • Reduce nutrient and water holding capacity• Increase dust during the dry season

Potential benefits of cover crops

• Increased soil organic matter • Weed suppression • Soil structure improvement • Pest and pathogen suppression • Promotion of beneficial soil microorganisms • Improved nutrient cycling/management• Increased water infiltration

Keep in mind…• Proper selection of cover crops is crucial

because many cover crop species may serve as hosts for P. penetrans

• White clover • Barley • Oat • Cereal rye

Photos by Brigid Meints

Field experiment: Cover crops and ground covers in established red raspberry alleyways

Objectives• Measure the effects of alleyway cover cropping in established red

raspberry on:• Soil quality—physical, chemical, biological• P. penetrans population dynamics• Soil microbial community structure• Plant competition

• Evaluate suitability of annual and perennial cover crops in PNW red raspberry production system.

http://www.almanac.com/plant/raspberries

Experimental design• Fall 2014-Fall 2016• Established commercial ‘Meeker’ red

raspberry field• History of RLN, but no root rot• CRD, 9 treatments, 4 reps, untreated

cultivated bare soil and weedy mown plots served as controls

• Treatment plots were 30 ft x 12 ft and spanned the entire alleyway on both sides of the row and a minimum of 60 ft were maintained between plots as buffer

• Treatments seeded twice over two years (once each fall)

Treatments• W1: Hard, red winter wheat cv. Norwest 553 (Triticum aestivum)• W2: Soft, white winter wheat cv. Rosalyn (T. aestivum)• O1: Winter-hardy oats cv. TAM 606 (Avena sativa)• O2: Winter-hardy oats cv. Nora (A. sativa)• G1: *Ryegrass (Lolium spp.) mix that included 51.25% intermediate ryegrass cv.

Tetralite and 48.24% tetraploid perennial ryegrass cv. Kentaur • G2: Perennial ryegrass (L. perenne) mix that included 43.93% ‘Esquire’, 31.44%

‘TopHat 2’, and 22.49% ‘Tetragreen’• T1: Triticale cv. Trical 103BB (Triticosecale sp.)• T2: Triticale cv. TriMark 099 (Triticosecale sp.)• R: Generic cereal rye (Secale cereale)• Mow: Control, weedy mow• Till: Control, bare soil, repeatedly rototilled (common industry practice)

Data collectionVariable Fall 2014 Spring 2015 Summer 2015 Fall 2015 Spring 2016 Summer 2016 Fall 2016SoilsBulk density x x x xPenetration x x x xNutrients (macro, micro, organic matter) x x x x xSoil microbiology x x x x xNematodes in soil x x x x xRaspberry plantsYield x xBerry weight & quality x xCane density x xNematodes in roots x x x x x

Take Home Message 1

Repeated cultivation did not significantly out perform ground cover treatments in any measured soil quality parameter.

Soil quality--physicalSpring 2015 Fall 2015

Spring 2016 Fall 2016

Lower bulk density =

less compaction=

better soil quality

Soil quality--chemical

• Cation exchange capacity (CEC), pH, % organic matter, N, P, K• Few significant differences among treatments.

Soil quality—biological

• Data forthcoming

Take Home Message 2

Alleyway cover crops did not significantly affect yield or plant performance.

Summer 2015 estimated yield and fruit quality

No significant differences in fruit yield or quality among treatments

Yield Fruit quality

Summer 2016 estimated yield and fruit quality

• No significant differences in fruit yield or fruit quality among treatments in 2016

• Fruit quality in all treatments was significantly higher than 2015

Yield Fruit quality

Take Home Message 3

Alleyway cover crops are maintenance hosts for P. penetrans, but vary in host suitability.

P. penetrans densities in alleyway soil

• P. penetrans population densities in soil were low in both years.• Till did not have significantly lower densities than many other treatments

in both years.

Spring 2015 and 2016 Fall 2015 and 2016

P. penetrans densities in bed soil

Spring 2015 and 2016 Fall 2015 and 2016

Average P. penetrans densities in bed vs. alley

Pp/100 g of soilBed Alleyway

Spring 2015 99 18Fall 2015 184 10Spring 2016 129 10Fall 2016 129 28

Take Home Message 4

Alleyway cover crops do not impact P. penetrans population densities in the raspberry crop.

P. penetrans densities in raspberry roots

Spring 2015 and 2016 Fall 2015 and 2016

P. penetrans populations were lower in most treatments in both the spring and fall in 2016.

P. penetrans densities in raspberry roots over time

Till

G2W2

G1Mow

Conclusions• Alleyway cover crops do not negatively affect raspberry yield or fruit

quality compared to bare soil alleyways.• Alleyway P. penetrans populations do not affect bed P. penetrans

populations.• Raspberry planted in plots with bare soil did not fare better than

raspberry planted in plots with cover crops under any measured parameter.

• P. penetrans population densities did not increase over time in raspberry roots.

• Cover crops were hosts for P. penetrans, but some were less suitable than others.

Alleyway cover crops: Pros vs. Cons• Pros:

• Lower bulk density when left to grow over time• Easier management with mowing compared to rototilling• Less expensive?• No increase in P. penetrans populations over time in raspberry

roots• No difference in yield or fruit quality compared to bare soil• Less dust/soil in the air during dry season• Less standing water in alleyways• Soil microbiological changes?

• Cons:• Cost of seed and planting• No increase in fruit yield or quality• Soil microbiological changes?

Acknowledgments

• Grower cooperator• Dr. Zasada’s lab• Dr. DeVetter’s lab• Northwest Agricultural Research Foundation• Washington Red Raspberry Commission

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