Location: Crop Improvement and Protection Research
Project Number: 2038-21600-001-000-D
Project Type: In-House Appropriated
Start Date: Oct 15, 2023
End Date: Oct 14, 2028
Objective:
Objective 1: Develop cropping system management strategies for organic and conventional high-value vegetable and strawberry production systems that increase climate resilience, improve nitrogen cycling and water quality, enhance soil quality, and improve weed management.
Sub-objective 1.A: Evaluate the effects of cover cropping frequency and compost on weed biomass during cover cropping and on weed density and weed management costs in subsequent lettuce and broccoli crops.
Sub-objective 1.B: Evaluate the effects of a legume-rye cover crop mixture versus non-legume cover crops at two seeding rates on weed suppression during cover cropping, and on weed densities and weed management costs in subsequent lettuce and broccoli crops.
Sub-objective 1.C: Evaluate the effects of cover cropping frequency and compost on subsequent lettuce and broccoli marketable yields.
Sub-objective 1.D: Evaluate the effects of a legume-rye cover crop mixture versus non-legume cover crops at two seeding rates on subsequent lettuce and broccoli yields.
Sub-objective 1.E: Evaluate the effects of a legume-rye cover crop mixture versus non-legume cover crops at two seeding rates on soil water storage during winter cover cropping.
Sub-objective 1.F: Use deep soil samples, column experiments, and on-farm samples to model previously overlooked pathways of nitrogen loss from compost.
Sub-objective 1.G: Develop farmer-friendly, field-based methods to predict the biomass and carbon to nitrogen (C:N) ratio of non-legume cover crops.
Approach:
The sub-objectives of the project are divided into the following two categories:
1. Long-term Salinas Organic Cropping Systems (SOCS) experiment. Sub-objectives 1.A to 1.F focus on vegetable yields, weeds, soil water storage and modelling of nitrogen loss pathways.
2. Ag Order 4.0 regulation cover crop nitrogen scavenging credits. Sub-objective 1.G continues and expands on-going short-term field studies to help growers get cover crop nitrogen scavenging credits in the Ag. Order 4.0 regulation.
The first six Sub-objectives (1.A to 1.F) will be addressed using unpublished data collected during the first 10 years of the SOCS experiment. This experiment began in 2003 and is the longest running trial in the U.S. focused on high-value, tillage intensive organic production systems. It includes 8 systems that for the first 8 years differed in cover cropping frequency, cover crop type, cover crop seeding rate, and compost rate. The experiment has two phases: the “intensive phase” (years 1 to 8) when management differed between systems, and the subsequent, and current “legacy phase” that monitors residual effects from the intensive phase. Commercial scale vegetable production was the focus during the intensive phase, whereas cover crops and occasional vegetables and strawberries are grown during the legacy phase. Data is collected on weeds, soil health, cash crop yields, cover crop services, and economics. The results of analysis from the first 20 years of the trial may indicate that there would be value in collecting additional field data during the remainder of the legacy phase or conducting additional analyses of archived soil samples. If this occurs additional data may be collected with existing or new collaborators.
During the next five years, the SOCS experiment will continue with a low intensity rotation of the ‘legacy phase’ that is an alternative to terminating long-term experiments that likely have some future value. During the project period at least six additional peer-reviewed papers from the existing unpublished data from the first 10 years will be published. The order in which the various components of the data will be published has been planned such that the papers build on each other and eventually provide a complete picture that addresses Objective 1.
Data to address Sub-objective 1.G will come from on-going and future replicated winter cover crop planting date trials at the USDA-ARS and on-farm plantings. In replicated trials, summer and fall cover crops will be planted with a grain drill and be irrigated as needed. Biomass samples will be harvested approximately every 30 days, oven-dried, and analyzed for total carbon and nitrogen. At each harvest, randomly chosen plants will be uprooted to measure the main stem length, and the Feekes growth stage. A similar approach will be used to evaluate the relationship between mustard stem length and biomass, and C:N ratio and growth stage.
