Improving and extending the superhero status of the sunn hemp to other growers in need of help

• 2008 annual report

We completed 6 demonstration trials in commercial vegetable farms in Hawaii to demonstrate the use of sunn hemp in conventional cover cropping system as well as in an improved cover cropping system (strip-till living mulch system). Extensive data were collected to demonstrate that strip-till sunn hemp living mulch system suppressed initial population densities of plant-parasitic nematodes and weed population densities, while enhancing beneficial free-living nematodes and soil microarthropods involved in soil nutrient cycling. This cover cropping system was able to extend the nutrient enrichment effect of sunn hemp cover cropping towards the end of a vegetable cropping cycle, a phenomenon that had not been shown in the conventional sunn hemp cover cropping system. Thus, we were able to enhance the sustainability of sunn hemp cover cropping beyond its conventional system. In addition, we also occasionally observed a suppression of insect pests in sunn hemp living mulch system. Unfortunately, we were not able to see positive outcomes from practicing sunn hemp row switching technique (switching rows between cash crop and cover crop rows between cycles). This could be due to technical difficulties in tracking planting rows in previos cropping cycle. Continuous efforts are underway to overcome this problem by practicing no-till planting. Multiple outreach routes were generated during this project period to promote the use of sunn hemp for Hawaiian vegetable growers as well as home gardeners. A bonus of this project is that we also convinced some fruit crop farmers (papaya and pineapple) to try out sunn hemp cover cropping. We are encouraged to documented that two cycles of sunn hemp cover cropping consistently increased crop growth or yield in this sunn hemp strip-till cover cropping system.

The overall goal of this project is to 1) enhance the sustainability of using sunn hemp cover crop, and 2) further advance the benefits of sunn hemp for suppressing nematode pests and enhancing beneficial soil microorganisms (free-living nematodes and soil microarthropods) demonstrated previously. To achieve these objectives, sunn hemp (SH) was planted for three months and compared to a fallow (F) with weeds treatments. Subsequently, alternate rows of sunn hemp were stripped-tilled. Then, cash crops will be planted over the strip-tilled rows. The remaining sunn hemp rows will be cut and residues left on the soil surface as organic mulch. The novelty of this project is the follow up of sunn hemp cover cropping system after the first cycle of cash crop. After the initial crop has been harvested, cash crop rows and organic mulch rows will be switched. Nematode community analysis was used to analyze soil health conditions.