Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/14/2006
Publication Date: 9/1/2006
Citation: Eigenberg, R.A., Nienaber, J.A., Woodbury, B.L., Ferguson, R. 2006. Soil conductivity as a measure of soil and crop status--a four year summary. Soil Science Society of America Journal 70:1600-1611. Online. Soil Science Society of America doi:10-2136/sssaj2005.0069. Available: http://soil.scijournals.org Interpretive Summary: Animal manure contains essential nutrients that can be valuable in raising crops. Managing those nutrients in environmentally friendly, cost effective ways can be challenging. Methods were tested to compare soil conductivity with soil nitrate over time. An irrigated field was used to study the effects of compost and manure on corn production. That study also used a winter cover crop to hold nitrate within the root zone. Soil conductivity measurements taken each two weeks during the growing season appear to be an indicator of N gains and losses in the soil. Therefore, it may serve as a measure of N sufficiency for corn early in the growing season and N surplus after harvest. The soil conductivity method also shows that a winter cover crop can reduce nitrate movement beneath the crop root zone. This real-time monitoring could be useful to farmers to improve nitrogen use and reduce nitrogen loss to the environment.
Technical Abstract: Animal manure can be an important resource in providing soil available N for 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 induction (EMI) soil conductivity and available N levels over four growing seasons in relation to manure/compost application and use of a green winter cover crop. A series (weekly surveys) of soil conductivity maps of a research cornfield were generated using global positioning system (GPS) and EMI methods with simultaneous soil samples. The study site was treated over a ten-year period with a winter wheat (Secale cereale L.) winter cover crop and no cover crop. The cornfield research site 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.). Sequential measurement of profile weighted soil electrical conductivity (ECa) was effective in identifying the dynamic changes in plant-available soil N, as affected by animal manure and N fertilizer treatments, during four 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 nitrate is most subject to loss. The EMI 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 crop management systems, and in minimizing N losses to the environment.