2012 Annual Report
1a.Objectives (from AD-416):
Develop ecologically-based soil and pest management strategies that enhance soil quality, nutrient cycling, and profitability, and reduce off-farm inputs in high-value, organic vegetable production systems.
Sub-objective 1.A. Evaluate the effects of cover cropping frequency and compost application on soil quality, vegetable yield and quality, and system profitability.
Sub-objective 1.B. Evaluate the effects of a legume-rye mix versus non-legume cover crops on vegetable yield.
Sub-objective 1.C. Evaluate the effects cover crop seeding rates on weed density and weed management costs in subsequent vegetable crops grown in rotation sequences.
Evaluate the energy efficiency, costs, and effectiveness of standard and alternative technologies and strategies for managing cover crop residue in high-value organic vegetable production.
Sub-objective 2.A. Compare fuel use, labor costs, and agronomic effectiveness of cover crop residue incorporation with standard primary tillage implements (disc-and-chisel) versus with an alternative implement (spader).
Sub-objective 2.B. Evaluate the roller-crimper implement for killing cover crops on beds for no-tillage organic vegetable production.
1b.Approach (from AD-416):
Organic production is increasing in the U.S., a response in part to public concerns about agricultural sustainability, food safety, & environmental quality. While farmers may consider moving to an organic system, continuity of economic viability during the transition from conventional to organic farming systems is a serious challenge. There is little scientific, organic-based information for farmers as they choose among the options available for the build-up of soil organic matter, maintenance of soil fertility, crops and cultivars, and disease and insect pest management practices. Improved understanding of the processes that occur during the transition to mature organic production systems is necessary to ensure the economic success of organic farming systems.
Research in organic systems is severely lacking despite the recent growth of the organic market. The research in this project occurs on certified organic land at the ARS and on collaborating farms and includes short-term component research and long-term systems research. The long-term systems research during the past year focused on crop rotations, soil fertility management, weed management, and cover cropping in high-value organic vegetable and strawberry systems. The short-term component research during the past year included a preliminary evaluation of winter cover cropped furrows in strawberry production systems. This research is applicable to small, medium and large-scale organic farms, and to conventional farms that are shifting to more sustainable soil management practices. This research involved collaboration on multidisciplinary projects with scientific and extension personnel from other agencies.
The ninth year of the long-term, multidisciplinary experiment with eight different organic systems for high-value organic crop production was completed in FY 2012. This ongoing study is the major focus of this project and is the longest running systems study in California on high-value organic vegetable and strawberry production systems. Data were collected on cover crop yield, weed biomass and densities, strawberry production, soil quality, soil microbes, and profitability. These data demonstrated the critical importance of using higher seeding rates for a legume-rye cover crop to maximize weed suppression in subsequent vegetables. The data also revealed that frequent cover cropping is much more important than compost application for maintaining vegetable yields and improving soil quality.
Long-term evaluation of cover crop biomass production and nitrogen accumulation in high-input, tillage-intensive production systems. Long-term research is needed to provide growers with reliable information on cover crop performance across years with variable winter climatic conditions. Cover crop biomass production and nitrogen accumulation were evaluated over eight winter periods in a rotational study with organic vegetables. ARS researchers in Salinas, California, found that rye and legume-rye produced 25 percent more cover crop biomass than mustard and that legume-rye accumulated 35 percent more nitrogen. This research provides growers with critical information to choose the most cost-effective cover crops to maximize organic matter inputs that can help maintain and improve soil quality and vegetable yields with minimal fertilizer inputs, and minimize nitrate leaching into ground and surface waters.
Brennan, E.B., Boyd, N.S. 2012. Winter cover crop seeding rate and variety effects during 8 years of organic vegetables 1. Cover crop biomass production. Agronomy Journal. 104:684-698.
Brennan, E.B., Boyd, N.S. 2012. Winter cover crop seeding rate and variety effects during 8 years of organic vegetables 2. Cover crop nitrogen accumulation. Agronomy Journal. 104:799-806.
Ferris, H., Sanchez-Moreno, S., Brennan, E.B. 2012. Structure, functions and interguild relationships of the soil nematode assemblage in organic vegetable production. Applied Soil Ecology. 61:16-25.