Project Overview
Commodities
- Agronomic: corn
- Animal Products: dairy
Practices
- Crop Production: double cropping
- Pest Management: chemical control, integrated pest management
Proposal abstract:
Many Pennsylvania dairy farmers have adopted double cropping annual forages as a sustainable intensification practice. This system has potential soil health and environmental benefits, but effects on weed management have not been studied. Studies suggest that repeated use of atrazine, an important corn herbicide, can result in enhanced microbial degradation. This would decrease the potential weed control benefits of using atrazine, although it may also reduce the environmental risks of atrazine run-off and non-target effects. In this project, we will test how different crop management practices affect atrazine persistence in soils from dairy cropping systems. We will also quantify microbial activity in these soils to determine the extent to which this effect is microbially mediated. We hope to identify if these sustainable intensification practices are reducing the persistence of an important corn herbicide, and which in-season manure management practices influence persistence. We propose to conduct soil sampling on dairy farms in Pennsylvania and use laboratory assays to assess atrazine persistence. Results will be shared with farmers, Extension agents, and researchers through presentations and publications to inform herbicide stewardship in these systems.
Project objectives from proposal:
Our overall objective is to understand how crop management legacy and in-season management practices affect the persistence, and thus efficacy, of atrazine in fields with atrazine history.
Specifically, we will:
Objective 1: Quantify the effects of crop management legacy on soil persistence of atrazine in fields with atrazine history.
Hypothesis 1: Soils from annual double cropping (ryelage/corn silage) systems will have lower degradation rates of atrazine compared to soils from a corn-soy rotation with no cover crops. We expect carbon inputs within annual double cropping systems that result from additional manure inputs and continuous living cover will provide an alternative food source for microorganisms, reducing their degradation of atrazine.
Objective 2: Test how in-season management practices of different manure sources affect atrazine degradation in soils from different crop management histories.
Hypothesis 2a: Addition of manure prior to the application of atrazine will reduce atrazine degradation rates in both management legacies but will reduce atrazine degradation rates more in the corn/soy rotation. We expect reduced degradation in both types of soils because microbes will use manure as a nitrogen source over atrazine. The effect size will be bigger in corn-soy rotation soils with lower soil organic matter.
Hypothesis 2b: Addition of digestate before atrazine application will reduce atrazine degradation rate compared to no manure addition, but increase it compared to adding regular manure because of a larger microbial population.
Objective 3: Determine the relationship between atrazine degradation rate in different treatments and microbial activity and diversity.
Hypothesis 3: Microbial activity and diversity will be higher in the annual double cropping treatments, and manure addition will further increase microbial activity. In response to atrazine application, there will be a larger increase in microbial activity in the corn-soy plots than in the annual double cropping treatments.