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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Research Project #436094

Research Project: Manure Legacy Impacts on the Soil Microbiome under Corn-Alfalfa Rotation

Location: Plant Science Research

Project Number: 5062-12210-003-29-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Apr 1, 2019
End Date: Mar 31, 2020

Objective:
The objectives of this work are to determine: 1) the impacts of dairy manure applications on soil microbial community structure and yield in forage cropping systems, and 2) the relationships between soil microbial community structure, nutrient-cycling functions, and soil edaphic characteristics in the context of forage-cropped agricultural soils.

Approach:
This study will be conducted at University of Minnesota Long-term Agricultural Research Network (LTARN) sites at three Research and Outreach Centers in Waseca, Lamberton, and Grand Rapids, MN. At each site, four microplots will be established within existing experimental plots representative of regional soil conditions. The four microplots (6 m x 6 m) will be assigned to one of the following treatments: 1. Agronomic recommended rate of cattle manure + fertilizer. One-time application of manure in spring 2019; from 2020 onward fertilizers added based on soil tests and established recommendations. 2. High rate cattle manure + fertilizer. One-time application of manure in spring 2019; from 2020 onward fertilizers added based on soil tests and established recommendations. Manure and fertilizer for yield goals that are 10-20% higher than expected. 3. Agronomic recommended Conventional Fertilizer: Annual fertilizers added based on soil tests and established recommendations. 4. Control: No nutrient inputs. Dairy manure and fertilizer will be applied to each appropriate plot in coordination with Cooperator. In the fall of 2019, two soil cores will be collected to a depth of 90 cm in each plot using a hydraulic sampling probe with a core inner diameter of 6.5 cm. One core will be used for soil chemical analysis and the other soil biological analysis. All cores will be subdivided into 0 to 15-, 15 to 30-, 30 to 60-, and 60 to 90-cm layers and be placed into placed polyethylene bags, transported on ice to Cooperator, and stored frozen (-80 °C) prior to processing. Genomic DNA will be extracted from frozen soil and microbial composition and diversity will be evaluated using high-throughput sequencing. Fungal and bacterial biomass will be estimated using qPCR. All library preparation and sequencing will be completed using Cooperator’s facilities. Soil samples for chemical analysis will be subsampled and analyzed for nitrate nitrogen, ammonium nitrogen, phosphorus (Bray test), Exchangeable potassium, total elements, pH, and electrical conductivity. Subsamples will also be analyzed for total C and total N. Corn and alfalfa dry matter (DM) yield will be determined by hand harvesting a subsample of plants in each plot and collecting wet-weights in the field. Subsamples will be dried at 65°C for 48 hours for DM determination and ground to pass through a 1 mm sieve.