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Title: CROP AND SOIL STATUS AS INDICATED BY ELECTRICAL CONDUCTIVITY SURVEYS OF A FIELD WITH COVER CROP AND MANURE AMENDMENTS

Author
item Eigenberg, Roger
item Nienaber, John
item FERGUSON, RICHARD - UNIV NEBRASKA
item Woodbury, Bryan

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Other
Publication Acceptance Date: 6/2/2003
Publication Date: 7/28/2003
Citation: EIGENBERG, R.A., NIENABER, J.A., FERGUSON, R.B., WOODBURY, B.L. CROP AND SOIL STATUS AS INDICATED BY ELECTRICAL CONDUCTIVITY SURVEYS OF A FIELD WITH COVER CROP AND MANURE AMENDMENTS. AMERICAN SOCIETY OF AGRI ENGINEERS SPECIAL MEETINGS AND CONFERENCES PAPERS. 2003. Paper #032338.

Interpretive Summary: Recycling of nutrients contained in livestock manure is essential for sustainable agriculture, but evaluation of nutrient availability is difficult. A three-year study was conducted to compare available nitrogen levels using electrical conductivity of soil. Treatments included manure/compost application and the use of a winter cover crop. Electrical conductivity of the soil was measured by using radio waves to penetrate the soil. The soil conductivity readings were combined with a global positioning system to produce field maps of soil conductivity. The mapping system was operated multiple times throughout the growing season. Changes in available soil N were shown to be affected by animal manure and commercial fertilizer treatments, during three corn growing seasons. This method identified that cover crops reduced the level of available soil nitrogen before and after the growing season, when nitrogen is most subject to loss. The electrical conductivity method for assessing soil condition gives an insight into changes of available nitrogen. These changes in available nitrogen have been confirmed by soil chemical analyses. The approach could be useful to farmers in optimizing nitrogen use for crops. This would also minimize nitrogen losses to the environment.

Technical Abstract: Animal manure can be an important resource in providing soil available N for crop plant needs. Management of animal manure to match crop needs throughout the crop growing season is one challenge for sustainable agriculture. This study was conducted to examine changes in electromagnetic (EM) soil conductivity and available N levels over three growing seasons in relation to manure/compost application and use of a green winter cover crop. A series of soil conductivity maps of a research cornfield were generated using global positioning system (GPS) and EM induction methods. The study site was treated over a ten-year period with a rye (Secale cereale L.) winter cover crop and no-cover crop. The plot was split for sub-treatments of manure and compost at rates matching either the P or the N requirements of silage corn (Zea mays L.). Data processing techniques were used to establish electrical conductivity treatment means for each of the growing season surveys. Sequential measurement of profile weighted soil electrical conductivity (ECa) was effective in identifying the dynamic changes in available soil N, as affected by animal manure and N fertilizer treatments, during three corn growing seasons. This method also clearly identified the effectiveness of cover crops in minimizing levels of available soil N before and after the corn growing season, when soluble N is most subject to loss. The EM method for assessing soil condition provides insights into the dynamics of available N transformations that are supported by soil chemical analyses. This real-time monitoring approach could also be useful to farmers in enhancing N use efficiencies of cropping management systems, and in minimizing N losses to the environment.