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Operation Background:

Hui Makaʻāinana o Makana is a community-based hui and nonprofit organization led by the lineal descendants of the Hāʻena ‘Ahupua‘a in Kauai. Their mission is to teach and carry forward the knowledge and practices of their ancestors “through the interpretation, restoration, care and protection of the natural and cultural resources that are located within the Hāʻena State Park.”

Hui Makaʻāinana o Makana, or the “Hui,” currently has a curatorship agreement with Hawaii State Parks in order for them to steward 15 acres of the Hāʻena State Park, which include an ancient lo’i, a poi mill, two historical homes, and historical grave sites.

The land the Hui cares for was historically a productive agricultural site with over 15 acres of lo‘i kalo, making it an important food source for the surrounding community. The land changed ownership several times after land privatization, and was eventually condemned by the state. It went unmanaged for many years before the Hui reinstated their stewardship.

In their historic lo’i, some of which are over 800 years old, the Hui primarily produces kalo directly for the community. Eric Hansen, the farm manager, along with other members of the hui and the surrounding community have worked to restore this historically important area and currently have around 7 acres in active rotation. The farm’s soils are of the Hanalei and Mokuleia series, which have moderate to high water holding capacity and are moderately to highly fertile.The area sees around 114 inches of rainfall a year.

Before the Hui began caring for this land, it suffered dramatic topsoil loss from previous management.

Now, Eric and the Hui have 7 acres in production, including lo’i and dryland crops. They primarily struggle with weeds, nematode issues, and germination/transplanting success in certain areas. A soil test they did showed low levels of both pest and beneficial nematodes, but may not have been a representative sample, and they want to implement proactive management practices as they are observing nematode impacts on their kalo.

Eric and the Hui grow wetland Kalo in lo’i and a variety of other crops in the fields. They have been using cover crops since they restored the lo’i system, and amend with fertilizer and spray organic pesticides when needed.

Soil Health Goals:

Eric and the Hui want to improve soil health to address weed and pest pressure, primarily nematodes, and reduce reliance on external inputs.

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Soil Health Practice 1: Mustard Biofumigation

The growing conditions at Hui Makaʻāinana o Makana will only support certain cover crop species during the summer months. Eric and his team will take advantage of that season to cover crop and biofumigate with daikon and white mustard, which have nematode-suppressing qualities (note: brown mustard is preferable for biofumigation but it was out of stock).They will follow CTAHR’s recommended methods for biofumigation which include seeding at 10lbs/acre, terminating and macerating the crop with a flail mower, rototilling the biomass 4-6 inches into the soil, and covering the area with black plastic for 7 days (fig 1).

Step-by-step protocol for effective biofumigation against plant-parasitic nematodes:

  1. Grow brown mustard or oil radish as cover crop at a seeding rate of 10 lb/acre (11 kg/ha) for 4-5 weeks (trap cropping is served at this time), producing dry biomass equivalent to 0.5-1.5 t/acre (1.2-3.7 t/ha).
  2. Macerate tissues using line trimmer or flail mower to enhance conversion of glucosinolates to isothiocyanates.
  3. Incorporate macerated tissues using roto- tiller to 4-6 inches (10-15 cm) soil depth (shallow till minimize soil disturbance).
  4. Cover black plastic mulch to contain isothiocyanates from escaping into the air.
  5. Uncover the plastic mulch 7 days after tarping then transplant cash crop seedlings immediately (avoid direct seeding of small seeded crops).

    source: Waisen and Wang 2018

Initially, Eric was looking for a nematode-suppressing cover crop species that he could plant during the winter months as well, but it would need to be tolerant to sea salt spray and low light. After consulting with experts at CTAHR, including Dr. Koon-Hui Wang, they determined that there is not a suitable species that could meet all of these conditions. Instead they chose to take advantage of mustard and radish during the summer growing conditions and use an alternate practice for the colder season.

Biofumigation for nematode and fungi control 2 14Fig 1: CTAHR-recommended soil health friendly biofumigation methods. Source: Wang et al 2022

Soil Health Practice 2: Crustacean Meal

Eric decided to use crustacean meal to address nematodes during the winter months. Crustacean meal is rich in chitin and encourages populations of microorganisms that feed on nematode eggs. For the soil building benefits, Eric and his team will still cover crop through the winter with salt-tolerant species including sunn hemp, radish, white oat, buckwheat, bundle king and white mustard.

In December of 2023, Eric planted cover crop using the species named above, discing the soil first, direct seeding with a hopper, discing once again, and covering the seeds with a screen to protect from birds. He removed the protective screen when the cover crop was at least 1 foot tall so the local nene couldn’t reach it. After discing to terminate the cover crop (not biofumigating), he will apply crustacean meal before planting kalo and flooding the lo’i —as long as the ground is dry enough, which may be a challenge in the winter months given the seasonal shadow effect of the mountain and the soil's ability to hold water.

Monitoring and Updates:

As of March of 2023, Eric has planted his winter cover crops but has not been able to apply crustacean meal yet as the soils have been too wet. He is waiting for the opportunity to do so.


Note: This material is based upon work supported by the U.S. Department of Agriculture, under agreement number NR2192510002C002. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the U.S. Department of Agriculture. In addition, any reference to specific brands or types of products or services does not constitute or imply an endorsement by the U.S. Department of Agriculture for those products or services.


Resources and References:

  1. Biofumigation approaches to help farmers reduce soil-borne disease pathogen problems in agroecosystems
    This CTAHR presentation describes how biofumigation with various cover crops can provide effective, affordable, and profitable ways to control pests like reniform and root-knot nematodes in Hawaii crops while improving soil health. It outlines numerous experiments that show the efficacy of allelopathic cover crops and biofumigation at controlling soil-borne disease pathogen problems in certain crops, and includes specific methods for biofumigation and results.
  2. Cover Crop Chart for Hawaii
    This cover crop selection chart lays out various types of cover crop used in Hawaii along with their various characteristics and uses, including whether they are a grass, broadleaf, or legume, their preferred elevation, seeding rate, annual or perennial status, and whether or not they are resistant to root-knot, reniform nematodes, and/or are suppressive to plant-parasitic nematodes.
  3. White Mustard
    This flyer outlines the environmental benefits, uses, and planting instructions for using white mustard as a cover crop.
  4. Trap Cropping and Biofumigation for Plant-parasitic Nematode Management
    This 2018 pamphlet by Philip Waisen and Koon-Hui Wang at UH Manoa explains best practices for cover cropping with oil radish and brown mustard to control plant-parasitic nematodes, including planting and terminations methods for best results.