A Superhero without a Cape: Using the Cover Crop Sunn Hemp to Feed the Soil, Suppress Nematodes and Smother Weeds

A Superhero without a Cape: Using the Cover Crop Sunn Hemp to Feed the Soil, Suppress Nematodes and Smother Weeds

Summary

Even though cover crops rarely provide direct cash returns, they’re rapidly proving their worth as off-season crops for helping to control insect pests, plant pathogens and weeds. They also reduce soil erosion, improve soil structure and nutrients and increase soil organic matter. Cerruti Hooks, a junior researcher with the University of Hawaii will use a Western SARE Professional + Producer grant to demonstrate the value of sunn hemp as a cover crop in cucumbers. Working with Khamphout Chandara of Waipahu, he’ll conduct field trials of sunn hemp to determine its impact on soil and its effectiveness at helping to manage nematodes, insects and weeds. Hooks will also quantify sunn hemp’s impact on cucumber productivity and marketable yield and encourage other growers to produce their own sunn hemp as a seed source. The strategies developed, he says, may apply to cropping systems other than cucumber.

The project, originally scheduled for completion Dec. 31, 2006, has been extended until June 30, 2007, because heavy rains destroyed the initial field trial set up on the cooperating farm.

Objectives/Performance Targets

• Teach the farmer/cooperator and others how to increase the economic viability of their farms by using the cover crop sunn hemp as part of an integrated pest management program
• Demonstrate how sunn hemp can be used to improve soil health and help manage weed and nematode pests
• Encourage the cooperating producer and others to grow their own sunn hemp for seed

Accomplishments/Milestones

The cooperating farmer has been growing sunn hemp for a year with the idea of supporting future farming operations. The ag professional has introduced a rotation scheme that can be integrated to attempt to reduce nematode populations. Field hands are now trained to identify symptoms of plant-parasitic nematodes. In the past, the workers and the cooperating producer were not familiar with nematodes nor could they recognize the damage they caused. They often mistook nematode damage as a fertility problem and applied additional fertilizer. The misdiagnosis and resulting increased fertilization had the potential indirectly heighten the problem and certainly increased production costs.

In addition to field work on the cooperating producer’s farm, the project team completed a field study on a separate farm owned by immigrants demonstrating how sunn hemp can also be used to help protect zucchini from viruses transmitted by aphids. Initial findings showed that interplanting sunn hemp with zucchini will works better at improving zucchini growth and marketable yields than intercropping it with a vegetable crop. The data from that study are being analyzed and results will be published in the future.

Impacts and Contributions/Outcomes

An extension article, written by project participants Cerruti Hooks, Koon-Hui Wang and Declan Fallon titled “An ally in the war against nematode pests:

Using sunn hemp as a cover crop to suppress root-knot nematode,” was published through the University of Hawaii at Manoa Cooperative Extension Service. Because Hawaii has a large population of immigrant farmers who speak little or no English, the article, written originally in English, has been translated into Thai, Lao, Cambodian and Ilocano. The purpose of the article is to show growers and stakeholders how sunn hemp can be used as a production tool to help suppress nematodes. It is being delivered to farms and is posted, in several languages, at www.ctahr.hawaii.edu/chahr2001/PIO/FreePubs/FreePubs08.asp#PlantDisease.

The outreach efforts to date have contributed to a significant volume of marketable cucumbers on the cooperating producer’s farm, helping sustain the economic viability. In addition, the help the producer with an aphid-transmitted virus that’s affecting his cucumbers, the project team is conducting a replicated study to assess whether sunn hemp, in addition to improving soil health and suppressing weed and nematode pests, can reduce the impacts of the virus on cucumbers. This is the first known study being conducted to evaluate sunn hemp potentials on these yield-reducing varieties.

Current plans are to conduct a field day/conference at the study site on the cooperating farmer’s operation, inviting growers, stakeholders and educators. Upon completion of the project, the various findings will be disseminated to the farmer community on a wider geographical scale. In addition, the project coordinator plans to evaluate sunn hemp in eggplant for its potential to suppress multiple pests associated with that crop.

Collaborators: