Pest control in vegetable crop is a challenge in tropical climate such as Hawaii. Plastic mulches
are often used but it is bad for the environment and difficult to remove. Living mulches provide a
reasonable alternative. Mint, a living mulch interplanting with a vegetable crop provides a high
return. In addition, it reduces soil erosion, retains moisture and nutrients. This farmer research
grant is geared to assist farmers in understanding the benefits of a mint living mulch and making
decisions on water and fertilizer inputs needed for successful adoption of mint living mulch in
their vegetable production. Eggplant (Solanum melongena ‘Waimanalo Long’) will serve as the
vegetable crop. Demonstration plots will be established. Data will be collected to compare
yields, soil quality and the profitability of mint living mulch using partial budgeting. The
sustainability of the mint living mulch vegetable cropping systems will be promoted through
field days and publications. Growers will be invited to the farm and see first-hand the mint living
mulch and be presented information on the economics of the mint living mulch, the yield of
eggplant and pest pressure experienced under the plastic mulch and the mint living mulch
cropping systems. The farmers will observe the different irrigation regimes. A second on-farm
field day will be held 6 months later and a third field day will be held 3 months before the project
terminates. This project will work with the University of Hawai‘i Extension Service to target
vegetables growers and new farmers for the workshops. A publication on vegetable mint living
mulch costs of production will be developed for use in the field days and accessible on the web
page. Finally, for each workshop and demonstration, an evaluation and feedback from the
attendees will be solicited, analyzed and improved.
Objectives of the project:
This farmer research grant is geared to assist farmers in understanding the benefits of a
mint living mulch and making decisions on water and fertilizer inputs needed for successful
adoption of mint living mulch in their vegetable production. The specific objectives of this
proposal are (1) to determine optimal irrigation and fertilizer for a mint living mulch vegetable
cropping system, (2) document pest and disease pressure in a mint living mulch vegetable cropping systems, and (3) demonstrate and promote the merits of the mint living mulch vegetable cropping system.
Objectives 1 and 2 are expected to be achieved as they have been demonstrated at the small
experimental plots at the University of Hawaii experiment station. The project will scale up to
two-thirds of an acre with irrigation, a manageable size for a small farm vegetable intensification production approach. Three on-farm field demonstration days and workshops will be conducted to ensure interested farmers can attend. Each workshop will last 4 hours. The establishment of the eggplant-mint living mulch will take 6-7 months from seed to the first harvests. The field days will be held beginning nine months into the project to demonstrate the experiments and present analyzed results of yield, profits, pest management, post-harvest handling and value-added mint when processed to oil.
The main plots are a strip plot design with irrigation. The 3 treatments of irrigation are low (15 minutes a day), medium (30 a day) and high (60 minutes a day). Each main plot was divided into 4 subplots, with randomized treatments of plastic mulch or a living mint mulch. After mint was established 6 eggplant cultivar meatball where transplanted into each subplot. The plants where fertilized with Sutane naturally slow release 8-2-4 nitrogen fertilizer and hand weeding was done as needed. Soil was sampled and the nematode community determined as a measurement of soil health. The first harvest done 2 months after transplanting.
The eggplants have just begun to yield. From these early harvests, the plants growing in the black plastic mulch treatment have provided the most fruit (66 fruit vs. 13 fruit). The eggplants growing in the mint living mulch are much smaller than those in the black plastic. The highest irrigation level has provided the most fruit compared to the medium and low irrigation treatments (30 vs. 26 vs. 23, respectively). Fruit weight was similar among treatments (100 gm average).
Educational & Outreach Activities
None to report now. The first field day is planned for March 2019.