Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 2004
Publication Date: November 4, 2004
Citation: Jaynes, D.B., Dinnes, D.L., Hatfield, J.L., Saleh, A., Arnold, J.G. 2004. The Effects of N-Fertilizer Practices on the Water Quality of Walnut Creek, Iowa [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, Wisconsin.
Walnut Creek drains 5,130 ha in the Central Iowa and Minnesota Till Prairies (MLRA) or Des Moines Lobe physiographic region. The maximum relief on the poorly dissected terrain is generally less than 5 m with internally drained prairie potholes common in the upper parts of the watershed. The Clarion-Nicollet-Webster soil association dominates the landscape. Subsurface tile drains and ditches installed over the past 120 years accelerate drainage and transport of several dissolved contaminants. Normal annual precipitation is 818 mm with 52% falling during May through August in relatively short, but intense events. Annual base flow constitutes 75% of the total stream discharge. Much of the remaining runoff is derived from subsurface drain inlets. About 80% of the watershed is in corn and soybean rotation; 3% in forage crops, 3% in pasture; 4% in woodland; and the remainder in small grains, transportation, and farmsteads. Stream nitrate concentrations periodically exceed the 10 mg nitrogen (N) L-l drinking water standard set by the United States Environmental Protection Agency (USEPA). Objectives for this Conservation Effects Assessment Project (CEAP) watershed study include: (1) Quantify the impact of intensive row crop agriculture on the water quality of a small watershed, (2) Quantify the impact of adopting the late spring nitrogen test (LSNT) best management practice for nitrogen fertilizer application to corn on N03 - concentration and load in subsurface drainage at the watershed scale, (3) Improve the management of N in soil by determining the temporal dynamics of N mineralization/immobilization in soil as affected by soil microbial biomass/activity, shoot and root residue inputs, labile organic matter pools, N fertility status, and tillage and improving synchronization between N availability in soil and N requirement by crop, (4) Improve air quality above and within corn and soybean crops by nutrient and tillage management practices, and (5) Assess the impact of current tillage and cropping practices on soil quality using the NRCS Soil Conditioning Index (SCI) and the Soil Management Assessment Framework (SMAF) being developed by the ARS and NRCS Soil Quality Institute.