Integrating cover crops for suppression of soil born diseases in blueberries

Final report for ONE16-285C

Project Type: Partnership
Funds awarded in 2016: $10,000.00
Projected End Date: 12/31/2017
Region: Northeast
State: New Jersey
Project Leader:
Dr. Peter Oudemans
Rutgers, The State University
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Project Information

Summary:

Highbush blueberry (Vaccinium corymbosum) is a long-lived perennial species grown in acidic soils that has been grown in NJ for nearly 100 years.  Typical cultivation practices emphasize “clean cultivation” where annual herbicide applications and frequent cultivation between the rows maintains a weed and cover crop free field. This practice, when implemented over the long term, results in a gradual reduction of soil organic matter (OM) and soil OM of less than 1.5% is not uncommon.   There are several potential detrimental effects of low soil OM and in this work we tested the effect of different cover crop treatments on the development of Phytophthora Root Rot (PRR). Soils for this experiment were collected from an ongoing field trial investigating various cover crops and soil amendments for improving soil health.  Thirty-six soil samples from six treatments (and six replicates) were collected from the field trial, sifted and placed in two 4-inch PVC pipe cut to 12 inch length and capped with weed matting and a rooted blueberry cutting (cv Duke) were transplanted into each one.  Half of the pipes were treated with Phytophthora and the other half left untreated.  Results show that use of horse manure as a soil amendment also resulted in the greatest reduction in the impact of PRR on blueberry cuttings.  This result corresponded with the horse manure also having the largest impact on soil OM increase.  Although we do not consider the results definitive because they represent only one season, they do fit our hypothesis that increased soil OM results in lower impact of Phytophthora root rot.  The use of a Phytophthora bioassay as a part of soil health testing procedures may provide valuable information when testing soil samples and evaluating cover crop programs. During the 2017 fall meeting growers were impressed with progress made and are more aware of issues surrounding soil health. One major challenge revealed here is that growers, in general, remain hesitant to implement a cover crop rotation before replanting because there is insufficient data demonstrating a return on investment. For example, two years of cover crop represents significant lost revenue for that acreage and it is unknown how that may benefit production.  Growers are more likely to utilize cover crops in row middles since the benefits are immediate and there is no negative economic impact.

Project Objectives:

Soils for this Northeast SARE project will be collected from cover crop field plots in the Conservation Innovation Grant (CIG) trial project located at Variety Farms in Hammonton, New Jersey and evaluated for their ability to suppress Phytophthora cinnamomi, a major blueberry soil pathogen. The CIG project will test soils from 12 cover crop treatments (see Table 1).  Soils for this Northeast SARE project will be collected from field plots representing 6 of the 12 treatments (see Materials and Methods), and tested using a greenhouse bioassay to evaluate disease suppressiveness; vegetatively propagated blueberry cuttings will be grown for 12 weeks in the soils. The bioassays will be conducted at three separate times during the course of the grant in spring, summer and fall.

Table 1.

 

Open Field Treatments

 

Spring

Summer

Fall

1

Control (bare ground)

   

2

Pine bark mulch

   

3

Compost

   

4

Sorghum-sudangrass

 

Cereal Rye

5

Sorghum-sudangrass

 

Rapeseed

6

Sorghum-sudangrass

Buckwheat

Cereal Rye

7

Sorghum-sudangrass

Pearl millet

Cereal Rye

8

Sorghum-sudangrass

Cowpea

Cereal Rye

9

Sorghum-sudangrass

 

Crimson Clover

10

Rapeseed

Cowpea

Cereal Rye

11

   

Native species

12

   

Fescue

Field days will be held at Variety Farms in August 2016 and 2017. Activities and talks will include a cover crop planting demonstration, bioassay setup demonstration, show-and-tell with pots from the bioassay, remarks on the current cover crop field trial, cover crop economics and recommendations, and grower question/answer. Attendees will be surveyed to assess their knowledge and intentions both before and after our demonstrations.

Introduction:

New Jersey, the birthplace of the modern highbush blueberry, is celebrating 2016 as the 100th year of blueberry production in the state. According to the USDA Agricultural Census, there are over 254 blueberry farms operating over 9,933 acres in the Garden State. The majority of these blueberry farmers are located in Atlantic and Burlington counties where sandy, low pH soils lend themselves to growing blueberries. At one time New Jersey ranked first among other states for pounds of berries harvested. In 2014, however, New Jersey production had fallen to fifth place. While other states have boosted annual yields, New Jersey has hovered around 7,000 pounds per acre for the past ten years. In comparison, California and Washington reported yields exceeding 10,000 pounds per acre in 2014. The perennial cropping system and multi-generational practices like clean culture, intense chemical inputs and tillage, and minimal carbon returns are likely contributing factors. Depleted soil organic matter and low microbiome diversity, as a result, limit crop potential in these tired soils.

Grower correspondence has confirmed annual yield declines in mature fields and revealed additional trouble with establishing new plantings. In September 2015, Rutgers University was awarded a Conservation Innovation Grant (principal investigator is the same as the project coordinator for this project) to evaluate the effectiveness of various cover crops to alleviate problems with new planting establishment and decline of mature bushes. The major goal of the CIG is to investigate soil microbiome diversity in relation to the health of blueberry bushes. The project will be evaluate cover crops which yield high biomass, act as biofumigants, and produce influential root exudates.

This SARE project will evaluate soil suppressiveness to Phytophthora cinnamomi, a major blueberry soil pathogen, in addition to the list of parameters we have committed to in the CIG. Our CIG soil health parameters include pH, cation exchange capacity, nutrient content, total carbon and nitrogen, percent organic matter, mechanical analysis, CO2 respiration (Solvita), nematode population density, and microbiome analysis. Soils from the CIG treatment plots will be evaluated for Phytophthora cinnamomi suppression in greenhouse bioassays using vegetatively propagated blueberry cuttings. The collective set of knowledge gained from the CIG and this SARE proposal will further our understanding of the complex relationship between soil health, yield, and sustainability.

Cooperators

Click linked name(s) to expand
  • Kate Brown
  • Dr. Thierry Besancon
  • Brandon Raso

Research

Materials and methods:

Overview: A large field trial to evaluate cover crops for improving soil health was established in the spring of 2015.  The trial includes 12 treatments with 6 replications in a randomized complete block design. For this work six treatments were selected based on biomass production as well as diversity of types of organic matter.  The following table describes the six treatments tested. 

Treatment

Spring

Summer

Fall

UTC

Untreated Control

 

 

Manure

Composted Horse Manure

 

 

SoRye

Sorghum-sudangrass

Sorghum-sudangrass

Cereal Rye

SoPMRye

Sorghum-sudangrass

Pearl Millet

Cereal Rye

SoCoRp

Sorghum-sudangrass

Cowpea

Rapeseed

PBark

 

Pine Bark Mulch

 

Soil was collected from each treatment and replicate/treatment and used to fill 12inch long by 4inch diameter PVC tubing sealed with weed mat on the bottom.  The soil filled tubes were placed in containers with 4″-6″ of water so that soil at the surface was saturated through capillary rise.  One year old rooted blueberry cuttings were selected for uniformity and trimmed to about 2″ above the original cutting.  One cutting was planted in each PVC tube for a total of 72 tubes.  Plants were uniformly fertilized with Jacks 20-20-20 All purpose greenhouse fertilizer as needed.

Phytophthora inoculum: An collection of two isolates of Phytophthora cinnamomi  from local commercial blueberry farms were used in this experiment.  Isolates were grown on V8-juice agar in petri dishes for 3-4 days before being cut into segments and placed in 10″ x 15″ glass pyrex baking pans filled with dilute V8-juice broth for 24hr.  The inoculum was washed by removing the dilute V8-juice broth and replaced with pond water to induce sporangium formation.  After 24hr the inoculum was checked for sporangia and zoospore release was induced by chilling the baking dishes for 1 hr in refrigerator and returning to room temperature.  Inoculum from all dishes/isolates was combined in a 1g plastic beaker and 36 plants (the other 36 were not inoculated) received an equal volume of zoospore inoculum.  Plants were inoculated 2, 4 and 6 weeks after planting and evaluations were made 12 weeks after planting. 

For evaluation the plants were removed from the tubes, roots were washed and weighed and rated on a scale of 1-5 (1 being the worst).  Each soil treatment was evaluated by comparing the impact of inoculation on shoot or root growth using a percent inhibition calculation.

 

Research results and discussion:

This project was overlaid on an ongoing NRCS cover crop project.  Here soil samples were collected from several cover crop treatments and assayed for suppressiveness (or conduciveness) to Phytopthora Root Rot. Following 1.5 years of cover cropping, trends were observed, however statistically significant results were not seen (KBrownNEPPSC_forSAREFinal). Of the three parameters measured, wet weight of roots was most informative.  Root rot ratings need to be refined to reflect symptoms and volume. Wet weight of shoots was most variable. Interestingly the uninoculated control gave the highest level of root growth (not significant) although this may be due to the vigor of the original planting material rather than a soil effect.  Overall, the percent inhibition of root weight demonstrated the relatively low impact of PRR on the root development with cow manure amendments, suggesting that this treatment has some impact.  However, soil amended with composted cow manure was most suppressive to root inhibition. In the analysis of organic matter, treatments with cereal rye showed an overall decline, however cow manure, SoCoRp, and Pine Bark all showed increases of approximately 0.4%.  Thus, although the results cannot be tied to organic matter we are continuing to work with this assay to better understand the interaction of cover crops with the soil microbiome and control of root disease.  Furthermore, in our field studies the impact of cover crop and soil OM on soil water content may have additional impacts on crop performance.  Therefore the Phytophthora bioassay will provide information on soil suppressiveness but other factors such as water holding capacity will also be important components of soil health.

 

Research conclusions:

Cover crops in blueberry soils are challenging because the low pH needed for blueberries can inhibit growth of many cover crop species.  Our results show promise that cover crops (in general) will have a positive effect, although no statistically significant effects were measured. We expected pine bark to show a stronger effect however larger quantities or more time may be required for the effect to be seen. Use of cereal rye, in general, showed a negative effect on organic matter build up. Use of tillage radish showed the most pronounced increase in organic matter. It is likely that soil amendments and cover crops would increase in effect if pH were first raised to levels more conducive to growth.

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

5 Consultations
1 Curricula, factsheets or educational tools
1 On-farm demonstrations
1 Published press articles, newsletters
1 Tours
5 Webinars / talks / presentations
5 Workshop field days

Participation Summary

504 Farmers
5 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Accomplishments

Survey – Soil Health Field Day 2016

Demonstration Plot Management 2016

Economics of Cover Crops – Handout

A soil health field day was held on August 23, 2016 at Variety Farms in Hammonton, New Jersey. A total of 26 people – including members of our NRCS-CIG grower committee, local NRCS agents, Rutgers researchers, and the local county agent – attended the event. The itinerary for the day is below:

Soil Health Field Day at Variety Farms – August 23, 2016

Time

Topic

Speaker

9:45 AM

Welcome (at packing house)

Dr. Peter Oudemans

 

Drive out to research plots

 

10:00 AM

Report on state of local blueberry farms and soils

Dr. Peter Oudemans

10:15 AM

Show-and-tell of demonstration plots, Q/A session

Kate Brown

 

Drive back to packing house

 

11:00 AM

Soil characterization based on microbiome analysis

Dr. Jim Polashock

11:15 AM

Cover crop economics; soil health and sustainability

Jack Rabin

11:30 AM

NRCS available funding for cover crop adoption

Nick Saumweber

11:45 AM

Lunch

 

12:15 PM

Grower survey and closing remarks

Dr. Peter Oudemans

After the talks, growers were surveyed regarding their pre- and post-event knowledge of cover crops as well as their intent to use cover crops. Responses to, “Within the next year, how likely are you to use cover crop or soil improvement practices demonstrated today?” are below:

Recommended Practice

Probably Won’t

Possibly Will

Probably Will

Definitely Will

Cover crops to build soil productivity

2

2

1

4

Specific cover crops for disease suppression

2

3

 

4

Permanent row middles cover crops

2

3

2

2

Composts or mulches amendments

1

1

2

5

Cover crops to suppress weeds

 

4

1

4

Summer cover crops

2

3

 

4

The results suggest that growers remain hesitant about soil health improvements, but are somewhat interested in cover crop adoption. One contributing factor may be that the information available to all of us after one season of cover crop trials cannot yield firm recommendations.

Cover crop demonstration plots at Variety Farms, Inc. in Hammonton, NJ continued to be managed through October 2016 at which point the last fall-seeded cover crops were seeded and later fertilized. A table has been attached that explained the management for each cover crop sequence this past growing season.

In the spring of 2017, soil samples were collected from demonstration plots located at a commercial blueberry farm near Hammonton NJ. These samples were potted and planted with vegetatively propagated blueberry cuttings and inoculated with Phytophthora cinnamomi. Following a twelve-week growing period, the blueberry cuttings were evaluated and preliminary conclusions drawn regarding soil suppressiveness to Phytophthora cinnamomi.

We shared this information with growers at several educational programs throughout 2017:

  • February 8, 2017 NJ Agricultural Convention & Trade Show,  Atlantic City, New Jersey
    • Attendance: ~60
    • 2:15- 2:45  Opportunities for Managing Soil Health in Blueberry Cultivation. — Kate Brown, George H. Cook Scholar, School of Environmental and Biological Science, Rutgers
  • February 21, 2017: Blueberry Open House at Frog Rock Golf and Country Club in Hammonton, NJ
    • Attendance ~90
    • 11:00-11:20 ‘Update on Blueberry Soil Health Studies with the Solvita Test System’ – Dr. Bill Sciarappa,
    • 1:25 – 1:45‘The Blueberry Stem Blight Complex’ – Dr. James Polashock
    • 1:45-2:05 ‘Strategies for Blueberry Disease Management’ – Dr. Peter Oudemans
    • 2:05-2:25 ‘An Update on pH’ – Dr. Gary C. Pavlis, Agricultural Agent, Rutgers
  • March 28, 2017 5:00-7:30  Blueberry Twilight Meeting:  Variety Farms, 548 Pleasant Mills Rd., Hammonton, NJ
    • Attendance ~90
  • April 27, 2017 5:00-7:30   Blueberry Twilight Meeting :Macrie Brothers Blueberry Farm , 7691 Weymouth Rd., (formerly Homestead Farm Building), Hammonton, NJ 
    • Attendance ~90
  • May 25, 2017 5:00-7:30 Blueberry Twilight Meeting: Atlantic Blueberry Company, 7201 Weymouth Rd., Mays Landing  NJ.
    • Attendance ~90

The primary education and outreach event for this project in 2017 was a stand alone field day:

  • September 7, 2017 9:30-2:00  2nd annual Soil Health Field Day. Variety Farms, Inc.
    • Attendance ~33 

The group was asked to complete a detailed questionnaire regarding cover crop practices and the results are described below. 

Blueberry Soil Health Field Day Survey – September 7, 2017

Circle the number that best describes your knowledge level, where

1 = no knowledge of the topic to 5 = expert knowledge

BEFORE Field Day

Topic

AFTER Field Day

1       2      3      4      5

NRCS Soil health & cover crops cost-share programs

1       2      3      4      5

1       2      3      4      5

Replanting cover cropping challenges & opportunities

1       2      3      4      5

1       2      3      4      5

Row middle cover crop selection & benefits

1       2      3      4      5

1       2      3      4      5

Soil productivity benefits from cover crops and OM

1       2      3      4      5

1       2      3      4      5

Winterkill cover crops

1       2      3      4      5

1       2      3      4      5

Cover crop soil-water holding capacity benefits

1       2      3      4      5

1       2      3      4      5

Composts & mulches to improve soil productivity

1       2      3      4      5

1       2      3      4      5

Managing cover crop species & mixes

1       2      3      4      5

1       2      3      4      5

Replanting cover crop selection and benefits

1       2      3      4      5

1       2      3      4      5

Disease & pest suppression from using cover crops

1       2      3      4      5

 

 

 

Survey Results

Average Scores

Question

Before

After

Diff

NRCS soil health and cover crops cost-share programs

2.9

4.1

1.3

Replanting cover cropping challenges and opportunities

2.4

4.0

1.6

Row middle cover crop selection and benefits

2.6

4.3

1.7

Soil productivity benefits from cover crops and OM

2.7

4.2

1.5

Winterkill cover crops

2.1

3.0

0.9

Cover crop soil-water holding capacity benefits

2.5

4.3

1.8

Composts and mulches to improve soil productivity

3.5

4.6

1.1

Managing cover crop species and mixes

2.3

4.2

1.9

Replanting cover crop selection and benefits

2.6

4.0

1.4

Disease and pest suppression from using cover crops

2.4

4.2

1.8

The results showed improvements in all of the categories however most improvement was seen in the areas related to use of cover crop mixtures, impact on water holding capacity and disease suppressiveness. Growers were very favorable on the use of cover crops in row middles and several have already implemented this practice.  Growers were most interested in understanding, measuring and evaluating the long-term benefits of cover crops.

Learning Outcomes

12 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Knowledge: Growers participated in a very active group discussion regarding the impact of increased soil OM on blueberry production.  Overall we found growers demonstrated a sound knowledge on the benefits of soil OM however, a key point was the lack of economic information on the benefits of soil OM.  For example, in a perennial crop such as blueberry it may take up to 4-years of cover crop to effect a change in soil OM.  Given this time frame, growers will experience a loss of revenue during the rotation and we are unable to provide an return on investment estimate for cover crop versus planting with no gap for cover crop.

Attitude: Growers recognize the importance of soil health and many are willing to utilize cover crops.  Impact of cover cropping on soil and root health are a major driver towards improving acceptance.

Skills:  In general growers are comfortable with Annual Rye and Sorghum as cover crops.  More work is needed to implement cover crops such as tillage radish, sunhemp, buckwheat, cowpeas, and rapeseed.

Awareness:  Increased occurrence of root disease and stress related disease such as stem blight (Botryosphaeria dothidea) have raised concerns among many growers.  By connecting these changes to soil health has helped raise awareness of the importance of soil health.

Project Outcomes

3 Farmers changed or adopted a practice
$75,000.00 Dollar amount of grants received that built upon this project
3 New working collaborations
Project outcomes:

Impacts

In this project we have have increased the number of growers practicing cover cropping.  This has been accomplished through demonstration and research.  Major challenges identified in this grant and our associated NRCS CIG grant include the problems of adapting cover crops with low pH conditions typical of blueberry culture.  Second, the use of cereal rye as a cover crop, which is a standard practice, will require addition of other cover crops such a tillage radish to increase soil organic matter.  As a result of this project growers are increasing the use of cover crops both in row middles and as a crop rotation as well as increasing the diversity of cover crop species. 

Assessment of Project Approach and Areas of Further Study:

This study represents a preliminary effort at educating growers and developing recommendations for utilizing cover crops in a perennial crop (highbush blueberries).   Although this work has successfully educated several growers on the benefits of cover cropping further work is needed to document economic benefits and continue to demonstrate biological benefits.  The problems of utilizing cover crops in a native crop where optimal pH for growth is below 5 clearly below the optimum for most cover crop species.  We are in the process of addressing these problems.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.