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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING AGRICULTURAL WATER QUALITY IN FIELDS AND WATERSHEDS: NEW PRACTICES AND TECHNOLOGIES Title: Landscape influence on soil carbon and nutrient levels

Author
item Logsdon, Sally

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 24, 2014
Publication Date: July 25, 2014
Citation: Logsdon, S.D. 2014. Landscape influence on soil carbon and nutrient levels [abstract]. In: 2014 Abstract Book, Soil and Water Conservation Society Annual Meeting, 7/27-30/2014, Lombard, Illinois. p. 88.

Technical Abstract: Past runoff, erosion, and management practices influence nutrient levels on the landscape. These starting levels affect future nutrient transport due to runoff, erosion, and leaching events. The purpose of this study was to examine closed-depression landscape effects on surface soil organic matter, extracted ortho phosphate (PO4), and nitrate(NO3), and ammonium (NH4) levels, and on well-water levels of total phosphorus (TP) and NO3. The sites examined include a field in Walnut Creek north watershed and two fields in the South Fork watershed of the Iowa river. For each field thirty sites were sampled from two transects. Three wells were installed in each field. LiDAR 1-m elevation data were cleaned up and used to determine slope, profile, and plan curvatures by a Python program, based on neighborhood points at 10 m range. Higher organic carbon was apparent for sites with low slope, low relative elevation, or curvature that was concave, converging, or linear. One field had long-term manure applications, and sites did not show any trend of landscape position with NO3, NH4, or PO4. Instead the loads of nutrients in this field were correlated with each other, and there was a site of high nutrient loads (0-0.15 m depth NO3 130 mg/kg, NH4 124 mg/kg, PO4 91 mg/L). The other two fields showed higher NO3 and PO4 for sites with low slope, low relative elevation, or curvature that was concave, converging, or linear. Results for NH4 were inconsistent. Overall, the manured field had higher levels of PO4 in the 0-0.15 m depth than the other fields, as well as high TP spikes in well water samples. Landscape tools were useful to show areas where surface soil was higher in nutrients. Uneven manure application might result in localized areas of high nutrient load.

Last Modified: 9/10/2014
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