Improving Soil Quality During and After Organic Transition

Project Overview

Project Type: Research and Education
Funds awarded in 2005: $145,509.00
Projected End Date: 12/31/2008
Region: North Central
State: Iowa
Project Coordinator:
Kathleen Delate
Iowa State University

Annual Reports


  • Agronomic: corn, oats, soybeans, wheat, hay
  • Animals: swine


  • Animal Production: manure management, feed/forage
  • Crop Production: cover crops, crop rotation, organic fertilizers
  • Education and Training: demonstration, extension
  • Pest Management: biological control
  • Soil Management: composting, soil analysis, organic matter, soil quality/health


    Over the 4 years of the study, soil quality at the Iowa State University Neely-Kinyon Long-Term Agroecological Research (LTAR) site was consistently higher in the organic rotations (containing corn, soybean, oats, and alfalfa in a three- or four-year rotation) relative to the conventionally managed corn-soybean rotation. Soils under organic rotations had greater soil organic carbon, total N, labile organic N; higher P, K, Mg and Ca concentrations; and lower soil acidity than the conventional system. Organic farms in the study showed similar high soil quality, despite differences in soil types, crop history, and amendment use.


    Organic agriculture continues to expand in the U.S. at a 7% rate in 2009, but strategies to optimize biological turnover to enhance soil quality in transitional organic farming are not well understood. In this project, we examined soil quality changes at a long-term organic research site established to examine the short- and long-term physical, biological, and economic outcomes of certified organic and conventional cropping systems. The ISU Neely-Kinyon Long-Term Agroecological Research (LTAR) farm is a systems experiment where treatments consist of a suite of farmer-developed practices (soil amendments, tillage, crop selection/rotation) established as complete management strategies. In addition, three on-farm organic sites were selected to monitor changes during the transition and beyond certification.

    Project objectives:

    In this research, we are testing the hypothesis that organic systems relying on locally derived soil fertility inputs are capable of providing stable yields, while maintaining soil quality and plant protection, compared to conventional systems with less diverse crop rotations and greater levels of external, fossil-fuel based inputs. This project was started in 2006 to building on farmer-based experiences and our long-term research program experience to address the following research objectives:

    Objective 1: Examine the effects of required organic farming practices, including crop rotations, cover cropping, compost application, and non-chemical weed control, on soil quality, crop yield and grain quality.

    Objective 2: Examine how soil organic matter (SOM) quantity and quality influence the interrelationships among soil fertility, crop resistance to pests and diseases, and environmental conservation of nutrients and carbon.

    Objective 3: Determine which crop rotations and nutrient management practices will increase the crop's competitiveness with weeds, build soil fertility, and maximize biological control of insect pests and diseases.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.