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Mustard Cover Crops in Apple Orchards in California, USA
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| Overview | Wild mustard covercrops can control weeds and improve nitrogen cycling in apple orchards. |
| Scale | field, patch, local region, community |
| Location | Watsonville, California, USA (36.6N, 121.5W) |
| Elevation | 0 to 150 meters |
| Climate | Mediterranean or Dry Summer Subtropical (Cs) |
| Agricultural Region | Mediterranean Agriculture - H |
| Population Density | >35 persons / square kilometer |
| Principle Crops | Semi-dwarf Fuji apples (Malus pumilla) |
| Domestic Animals | none |
| Soils | Mountain Soils - Xeric great group of Alfisols, Entisols, Inceptisols, Mollisols and Ultisols |
| Natural Vegetation | Needleleaf evergreen trees (E), Douglas fir- Redwood (29) |
| Ecoregion | Mediterranean Province |
| Basic Principles addressed | Use Renewable Resources, Minimize Toxics, Manage Ecological Relationships, Diversify, Value Health |
| Page Author and Date | Chris Bley from studies by Steve Gliessman |
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Herbicides are used extensively in conventional orchards to suppress the growth of invasive weeds. Cover cropping is an environmentally-sound solution for weed control, but to be effective, cover crops must exclude weeds without inhibiting crop growth. Several different types of cover crops and the use of a plastic tarp were compared to conventional practices in inhibiting weed growth between young Fuji semi-dwarf apple trees in Watsonville, California, USA. Within forty-five days after emergence, wild mustard (Brassica kaber) had displaced all other weed plants and accounted for 99% of total weed biomass in experimental plots. Other weed cover crops achieved far less dominance, representing no more than 42% of the weed biomass. These results demonstrate that mustard was the only cover crop that controlled weeds as effectively as conventional herbicides or the plastic tarp. |
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Wild mustard has proven effective as a cover crop for weed suppression in apple orchards converting from conventional to organic management. Mustard's ability to grow fast and smother other plant growth is achieved by its allelopathic inhibition of other weeds. Glucosinolates, a chemical found in most species of the genus Brassica (including mustard) inhibit weed seed germination. Moreover, apple production and tree growth rate were improved in mustard cover plots relative to the conventional plots. Nitrogen stored in mustard biomass was returned to the soil when the cover crop was cut down in the spring, enhancing nutrient cycling. Mustard cover crops also attract beneficial insects during their flowering period. |
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Use Renewable Resources Planting mustard cover crops uses renewable resources instead of non-renewable resources to control weed growth. Cover cropping recycles on-farm nutrients when biomass is returned to the soil. Minimize Toxics Mustard cover crops eliminate the use of toxic herbicides. Nitrate contamination has also been linked with herbicide control of weeds. Manage Ecological Relationships Use of an allelopathic cover crop helps to manage weeds instead of controlling them. When mustard biomass is returned to the orchard's soil, nutrient cycling is enhanced. Diversify Mustard cover crops increase biodiversity by attracting beneficial insects and increasing plant species diversity in orchards. Value Health Non-toxic forms of weed control and fertilization eliminate environmental pollution. |
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Gliessman, S.R., 1987. Species interactions and community ecology in low external-input agriculture. American Journal of Alternative Agriculture. 11:160-165 Paulus, J., 1994. Ecological aspects of orchard floor management in agroecosystems of the central California coast.
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