Water Management Effects on Mineralization of Soil Organic Matter and Corn Residue
1995
Kimmelshue, J. E. | Gilliam, J. W. | Volk, R. J.
Water table control is being used on large areas of poorly drained Atlantic Coastal Plain soils during the winter to reduce N losses to surface waters. This study was conducted to determine the effect of water table depth (WTD) and control on N mineralization of added corn (Zea mays L.) residue. Soil columns (15-cm-diam.) were extracted to 70-cm depth from a Portsmouth loam (fine-loamy over sandy or sandy-skeletal, mixed, thermic Typic Umbraquult), placed in polyvinyl chloride (PVC) water table columns, and buried even with the surrounding soil surface. Labeled corn residue (18.01 atom % excess ¹⁵N) was incorporated in the upper 15 cm of the PVC columns and WTDs of 0, 15, 30, and 45 cm maintained. Soil microsamples were taken over time for N analyses. After 209 d, approximately 8 to 13% of the inorganic N came from the N added as plant residue, even though the added N was only 1.1% of the total soil N. Although the 0- and 15-cm WTD treatments accumulated little ¹⁵NO₃-N, they contained appreciable ¹⁵NH₄-N. In contrast, the 30- and 45-cm WTD treatments accumulated primarily ¹⁵NO₃-N as inorganic N accumulation increased with time and rising soil temperatures. It was concluded that WTD control could be used during the winter to promote denitrification of available NO₃-N and thus to minimize NO₃-N lost to drainage water.
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