Integrating cover crops for suppression of soil born diseases in blueberries

View the project final report

• 2016 annual report

Commodities

• Fruits: berries (blueberries)

Practices

• Crop Production: cover crops
• Education and Training: on-farm/ranch research, technical assistance, workshop
• Pest Management: biofumigation, biological control, cultural control
• Soil Management: composting, soil analysis, soil quality/health

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.

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.