Integrating cover crops for suppression of soil born diseases in blueberries

Integrating cover crops for suppression of soil born diseases in blueberries

Summary

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.

Objectives/Performance Targets

Soils will be collected from cover crop field plots in the CIG trial located at Variety Farms in Hammonton, New Jersey and evaluated for their ability to suppress Phytophthora cinnamomi, a major blueberry soil pathogen. The project will test soils from 12 cover crop treatments (see Table 1).  Soils will be collected from field plots 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.

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.

Accomplishments/Milestones

Survey - Soil Health Field Day 2016Demonstration 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:

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:

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. At the same meeting in 2017, grower intent and attendance is expected to be higher. Not only will we have more information, but we also have several opportunities to share our findings with growers beforehand. These opportunities are described below:

- January 2017: winter meeting with NRCS-CIG grower committee at Rutgers Marucci Center in Chatsworth, NJ
- February 8, 2017: New Jersey Agricultural Convention in Atlantic City, NJ
- February 21, 2017: Blueberry Open House at Frog Rock Golf and Country Club in Hammonton, NJ
- March, April, and May 2017: Twilight meetings held at various blueberry farms in Atlantic County, NJ

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.

Impacts and Contributions/Outcomes

In the spring of 2017, soil samples will be collected from the demonstration plots at Variety Farms, Inc. These samples will be potted and planted with vegetatively propagated blueberry cuttings. Following a twelve-week growing period, the blueberry cuttings can be evaluated and preliminary conclusions can be drawn regarding soil suppressiveness to Phytophthora cinnamomi. We intend to share this knowledge with the growers at the August 2017 soil health field day. Until that time, we cannot share grower intent to adopt cover crops based solely on information about the potential to suppress Phytophthora cinnamomi.