Impacts of Cover Crops on Phosphorus and Nitrogen Loss with Surface Runoff

September 25, 2017

Impacts of cover crops on phosphorus and nitrogen loss with surface run off
Funded by the Iowa Nutrient Reduction Strategy

Issue: Cover crops are a recognized conservation practice to reduce soil erosion, and Iowa research has shown a winter cereal rye cover crop greatly reduces nitrate loss with subsurface drainage. However, little research has evaluated the impact of cover crops on total and dissolved nitrogen (N) and phosphorus (P) loss with surface runoff.

Objective: This project will continue an existing study for two more years, conducted under natural rainfall, to evaluate impacts of a winter cereal rye cover crop on soil, N, and P loss with surface runoff in a field testing high in P, managed with a corn-soybean rotation. Approach: Systems evaluated in 12 areas ranging from one to three acres are chiselplow/disk tillage and no-tillage with or without a cereal rye cover crop seeding each year. Soil samples for the late-spring nitrate test are collected when corn is 6 to 12 inches tall. Dry matter yield and total P and N are measured in rye cover crop samples collected each spring and fall to study nutrient uptake and recycling into the soil. Grain yield, grain N and P concentrations, and removal are measured each year. Runoff from the test areas is analyzed for total solids and several P and N forms.

Investigators: Antonio Mallarino, Professor, Agronomy, Iowa State University Matthew Helmers, Professor, Agricultural and Biosystems Engineering, Iowa State University Richard Cruse, Professor, Agronomy, and Director, Iowa Water Center, Iowa State University John Sawyer, Professor, Agronomy, Iowa State University Dan Jaynes, Soil Scientist, USDA-ARS National Laboratory for Agriculture and the Environment

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