- Additional Plants: herbs
- Miscellaneous: mushrooms
- Crop Production: biological inoculants
- Education and Training: extension, on-farm/ranch research, youth education
- Pest Management: allelopathy, biological control
- Production Systems: organic agriculture
- Soil Management: organic matter
- Sustainable Communities: social networks
The overall objective of this project was to examine if recycling spent oyster mushroom compost could help farmers manage plant-parasitic nematodes in the field. Six laboratory and two field trials were conducted for this project. In the four laboratory mushroom compost amendment trials, mushroom compost amended potting mix (peat moss or yard waste compost) planted with zucchini seedlings or without seedlings suppressed root-knot nematodes (Meloidogyne incognita) compared to unamended potting mix. However, the mushroom compost amendment did not suppress plant-parasitic nematodes if the potting mix did not contain sufficient organic matter (e.g. sand: soil mix at 1:1 v/v). Spent oyster mushroom compost collected from a local oyster mushroom grower was used to prepare mushroom compost water extract (MCWE) by soaking the compost into water at more than 25% brewed with air pump overnight. This reduced mobility of root-knot nematodes by more than 68.5% in the first MCWE trial. In the second MCWE trial, 10% MCWE reduced nematode mobility by 87.8%. However, the MCWE did not kill all the nematodes but rather paralyzed most of them. Based on these laboratory results, the next step in this project was to use oyster mushroom compost as basil seedling amendment in the transplant potting media and drenching MCWE to basil rhizosphere to provide post-plant nematode management. Two basil field trials were conducted at 1) Poamoho Experimental Station in Waialua (Trial I), and 2) at Magoon Teaching Facility in Manoa (Trial II), HI. Soil organic matter was used to enhance activities of oyster mushroom compost. Buckwheat was planted as a cover crop prior to basil planting in Trial I, whereas yard waste compost mulch was used as surface organic mulch in Trial II. Unfortunately, both mushroom amendment and MCWE drenching did not suppress numbers of plant-parasitic nematode in both field trials. However, soil health improved in the mushroom compost treatments based on nematode community analysis conducted by quantifying the free-living nematodes. In Trial I, regardless of cover cropping, mushroom amendment and drenching had increased abundance of bacterial feeding nematodes, enrichment index (EI) and reduced channel index (CI), indicating an enhancement of the bacteria decomposition pathway, and thus, a more enriched soil food web. Similar soil food web enrichment effect was observed toward the end of Trial II. In addition, mushroom amendment alone also increased abundance of omnivorous nematodes and structure index (SI) when used in conjunction with yard waste compost mulch, indicating a more structured soil food web compared to no mushroom amendment. In this trial, nematode richness was also higher in mushroom amended compared to non-amended plots. Drenching with MCWE did not affect free-living nematodes in Trial II. Despite the obvious improvement of soil health by mushroom compost treatments, basil yield was not improved by these treatments, in part due to downy mildew infection in both trials. Mushroom amendment and MCWE drenching increased basil plant growth but not yield in Trial I. In Trial II, mushroom amendment and MCWE drenching did not improve basil growth and yield, but the yard waste compost mulch did.
Three extension articles, one student symposium poster, and three symposium/conference presentations were generated. A student M.S. thesis focused on this project is at completion stage. Two high school students adopted this project as their high school science fair project for two consecutive years. A website was created to update the public about our new findings. Two display booths were exhibited at the University of Hawaii College of Tropical Agriculture and Human Resources (CTAHR) Annual Organic Field Day and Centre of Rural Agricultural Training and Entrepreneurship (CRATE) Field Day.
Plant-parasitic nematodes are prevalent pests in nearly all vegetable crops in tropical climates in Hawaii (Schmitt and Sipes, 1998). Many farmers are looking for alternative methods to chemical approaches for managing nematodes in the soil. Oka (2010) had reviewed the effects of a series of organic amendments including animal and green manures, compost, and nematode-antagonistic plants on suppressing plant-parasitic nematodes. A type of compost that is known to secrete toxic compounds against nematodes but has not received enough attention is the oyster mushroom compost. Gray oyster (Pleurotus ostreatus) and King oyster mushrooms (Ali’i) (Pleurotus eryngii) are two common commercially produced oyster mushrooms in Hawaii. Pleurotus ostreatus is known to exude a toxin from the fungal hyphae, known as trans-2-decenedioic acid (Kwok, 1992). This toxin paralyzes the nematodes on contact, which allows the hyphae to move into position to colonize and digest the nematode. Studies on the effects of oyster mushroom on nematodes have been predominantly in vitro. Palizi et al. (2009) demonstrated the use of mushroom compost with sugar beets (Beta vulgaris) in the field by directly incorporating the mushroom compost into soil at 3% (w/w). The mushroom compost suppressed more than 85% of sugar beet cyst nematode (Heterodera schachtii) cysts. Although direct incorporation of the mushroom substrate into the soil could ensure direct contact of the mushroom mycelia with the root system, the amendment rate needed for nematode suppression using this approach could be unfeasible in the field- or even at the garden-scale if an ample supply of the mushroom compost is not available.
This project evaluated the optimum amendment rates and drenching concentrations. Utilizing the results from the laboratory, two field experiments were conducted using mushroom compost amendment and the MCWE drenching for plant-parasitic nematodes. Soil health was also evaluated with nematode community analysis. This project explored different approaches to use mushroom compost for the suppression of root-knot nematodes (Meloidogyne incognita) through: 1) direct incorporation of the mushroom compost amendment into the soil before crop planting, 2) drenching mushroom compost water extract into the root system after crop planting, and 3) amending mushroom compost into the growth media of transplant trays. Several factors might affect the applicability and efficacy of nematode suppressive effects of mushroom compost. These include mushroom species, mushroom compost amendment rate, concentration of mushroom compost water extracts, and local availability of the compost.
The overall goal of this project is to explore the potential of spent oyster mushroom compost for managing M. incognita on basil. Specific objectives were to:
- determine the amendment rate of spent Pleurotus compost in organic potting medium against M. incognita;
- establish a mushroom compost water extract (MCWE) concentration for incognita suppression; and
- demonstrate a mushroom compost based technology for pre- and post-plant nematode management on basil in the field.
Laboratory experiments were conducted to evaluate mushroom compost amendment rates of two Pleurotus species, and concentrations of mushroom compost water extract against root-knot nematode (Meloidogyne incognita). Two field experiments were conducted at two locations to evaluate the benefits of mushroom compost amendment and MCWE drenching.