Project Highlights
FUNDED PROJECT RESULTS
Central California study sheds light on cover crop management for weed suppression
Project title: The effect of cover crop seeding rate, planting arrangement, and mixture composition on cover crop performance on organic vegetable farms on the Central Coast of California
OFRF project funding was awarded in Fall 2004 and Fall 2002. A final report describing project results was submitted in August 2007. A project summary was issued in OFRF's Information Bulletin No. 17. See also OFRF's researcher profile of Dr. Brennan.
Investigator: Eric Brennan, USDA-Agricultural Research Service, Salinas, CA
Project location: California Central Coast vegetable farms
Eric Brennan/USDA-ARS
Cover crop mix trial 4, Hollister, California, March 2004.
Cover crops are key components of crop rotations on organic farms in the Central Coast of California and affect soil quality, nutrient cycling, and pest and disease management. Many organic farmers in this region cover crop each field every 1 to 3 years. Common cover crops in the area include monocultures of cereals or mustards, and mixtures of cereals and legumes. To optimize cover crop benefits, organic farmers need more information on how seeding rate, planting arrangement, and mix composition affect cover crop biomass production and weed suppression.
The research described here focused on the effects of cover crop seeding rate, planting arrangement, and mix composition on cover crop biomass production and weed suppression during the winter cover cropping period on organic cool season vegetable farms on the central coast of California. The research occurred on two commercial organic farms and the on USDA-ARS certified organic research farm between October 2003 and April 2005 and included five trials.
 
Eric Brennan/USDA-ARS
Left: Seed sample from mix 1 with 10% ‘Cayuse’ oats, 35% bell bean, 25% ‘Magnus’ pea, 15% purple vetch, and 15% common vetch. Right: Seed sample from mix 2 with 40% ‘Cayuse’ oats, 23% bell bean, 17% ‘Magnus’ pea, 10% purple vetch, and 10% common vetch.
Trials 1 to 3 evaluated weed and cover crop growth of rye and a legume/oat mixture planted at three seeding rates in a one-way versus grid planting arrangement. Weed suppression increased with increasing seeding rate. Cover crop biomass production was higher early in the season at the higher seeding rates but final biomass production was not affected by seeding rate. Planting arrangement did not affect weed or cover crop growth of the legume/oat mixture. However, rye biomass was higher and weed biomass was lower in the grid planted rye cover crop during one year.
Eric Brennan/USDA-ARS
Cover crop field day focused on mixes, February, 2004.
Trials 4 and 5 evaluated weed and cover crop growth of several monoculture cover crops and 17 mixtures of legumes, oat, rye and mustard. Cover crop biomass production was usually higher in nonlegume than in legume monocultures, and weed biomass was usually less in the nonlegume monocultures. Biomass production and weed suppression by the mixes varied considerable between years and sites. In the first year, weed biomass was in order of legume/oat>legume/rye>legume/mustard at both sites, but this pattern did not occur in the second year. Increasing the non-legume proportion in a mixture usually increased weed suppression but also reduced growth of the legume component.
More research is needed to better understand the complex competition dynamics in cover crop mixes to develop mixes that scavenge nitrogen, suppress weeds, but also allow adequate growth and nitrogen fixation by the legume component.
Contact:
Eric Brennan
Research Horticulturalist
USDa-ARS
1636 E. Alisal St.
Salinas, CA 93901
(831) 755-2822
ebrennan@ucdavis.edu
|
Collaborators:
Richard Smith, University of California Cooperative Extension, Salinas, CA;
Nathan Boyd, Nova Scotia Agricultural College, Truro, NS;
Phil Foster, Phil Foster Ranches, San Juan Bautista, CA;
Ron Yokota, Tanimura & Antle, Salinas, CA.
|
OFRF funding awarded:
Fall 2004: $14,700 (year 2)
Fall 2002: $14,360 (year 1)
Funding category: Research
This project was funded in partnership with EPA Region 9.
|
|
