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University Heights, IA, United States

Jaynes D.B.,2110 University Blvd | Isenhart T.M.,Iowa State University
Journal of Environmental Quality

Riparian buffers are a proven practice for removing NO3 from overland flow and shallow groundwater. However, in landscapes with artificial subsurface (tile) drainage, most of the subsurface flow leaving fields is passed through the buffers in drainage pipes, leaving little opportunity for NO3 removal. We investigated the feasibility of re-routing a fraction of field tile drainage as subsurface flow through a riparian buffer for increasing NO3 removal. We intercepted an existing field tile outlet draining a 10.1-ha area of a row-cropped field in central Iowa and re-routed a fraction of the discharge as subsurface flow along 335 m of an existing riparian buffer. Tile drainage from the field was infiltrated through a perforated pipe installed 75 cm below the surface by maintaining a constant head in the pipe at a control box installed in-line with the existing field outlet. During 2 yr, >18,000 m3 (55%) of the total flow from the tile outlet was redirected as infiltration within the riparian buffer. The redirected water seeped through the 60-m-wide buffer, raising the water table approximately 35 cm. The redirected tile flow contained 228 kg of NO3. On the basis of the strong decrease in NO3 concentrations within the shallow groundwater across the buffer, we hypothesize that the NO3 did not enter the stream but was removed within the buffer by plant uptake, microbial immobilization, or denitrification. Redirecting tile drainage as subsurface flow through a riparian buffer increased its NO3 removal benefit and is a promising management practice to improve surface water quality within tile-drained landscapes. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

Singer J.W.,2110 University Blvd | Chase C.A.,2110 University Blvd | Kohler K.A.,Iowa State University
Agronomy Journal

Productivity rather than profitability is often used to compare agronomic systems. The objective of this study was to compare profitability of moldboard plow, chisel plow, and no-tillage with or without composted animal manure in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.)/clover (Trifolium spp.) rotation during three rotation cycles. Corn and soybean grain and seed yield exhibited a tillage × compost amendment interaction. Yield in moldboard and chisel plow with or without compost was similar, but yield in no-tillage with compost was 8 and 5% greater than without compost for corn and soybean. Wheat yielded 5% higher in moldboard and chisel plow than no-tillage and 4% higher in compost than no-compost amendment. Wheat returns were similar among tillage and 7% higher when compost was amended. Corn production with or without compost amendment had similar returns in moldboard plow. Corn in chisel plow with compost had 8% greater returns than the no-compost treatment. Corn in no-tillage with compost had 15% greater returns with compost amendment than without. Similar corn returns were generated for all tillage systems if compost was applied. Soybean production using no-tillage had 9% greater returns than without compost and greater returns than moldboard and chisel plow with or without compost. Summing returns across the three-crop rotation indicated cycling nutrients through compost application exhibits a functional synergy in no-tillage and chisel plow but not moldboard plow for these crops, which enhances their profitability. © 2010 by the American Society of Agronomy. Source

Kroger R.,Mississippi State University | Dunne E.J.,St. Johns River Water Management District | Novak J.,U.S. Department of Agriculture | King K.W.,Soil Drainage Research Unit | And 6 more authors.
Science of the Total Environment

This review provides a critical overview of conservation practices that are aimed at improving water quality by retaining phosphorus (P) downstream of runoff genesis. The review is structured around specific downstream practices that are prevalent in various parts of the United States. Specific practices that we discuss include the use of controlled drainage, chemical treatment of waters and soils, receiving ditch management, and wetlands. The review also focuses on the specific hydrology and biogeochemistry associated with each of those practices. The practices are structured sequentially along flowpaths as you move through the landscape, from the edge-of-field, to adjacent aquatic systems, and ultimately to downstream P retention. Often practices are region specific based on geology, cropping practices, and specific P related problems and thus require a right practice, and right place mentality to management. Each practice has fundamental P transport and retention processes by systems that can be optimized by management with the goal of reducing downstream P loading after P has left agricultural fields. The management of P requires a system-wide assessment of the stability of P in different biogeochemical forms (particulate vs. dissolved, organic vs. inorganic), in different storage pools (soil, sediment, streams etc.), and under varying biogeochemical and hydrological conditions that act to convert P from one form to another and promote its retention in or transport out of different landscape components. There is significant potential of hierarchically placing practices in the agricultural landscape and enhancing the associated P mitigation. But an understanding is needed of short- and long-term P retention mechanisms within a certain practice and incorporating maintenance schedules if necessary to improve P retention times and minimize exceeding retention capacity. © 2012 Elsevier B.V. Source

Kalkhoff S.J.,U.S. Geological Survey | Hubbard L.E.,U.S. Geological Survey | Tomer M.D.,2110 University Blvd | James D.E.,2110 University Blvd
Science of the Total Environment

Precipitation patterns and nutrient inputs affect transport of nitrate (NO3-N) and phosphorus (TP) from Midwest watersheds. Nutrient concentrations and yields from two subsurface-drained watersheds, the Little Cobb River (LCR) in southern Minnesota and the South Fork Iowa River (SFIR) in northern Iowa, were evaluated during 1996-2007 to document relative differences in timings and amounts of nutrients transported. Both watersheds are located in the prairie pothole region, but the SFIR exhibits a longer growing season and more livestock production. The SFIR yielded significantly more NO3-N than the LCR watershed (31.2 versus 21.3 kg NO3-N ha-1 y-1). The SFIR watershed also yielded more TP than the LCR watershed (1.13 versus 0.51 kg TP ha-1 yr-1), despite greater TP concentrations in the LCR. About 65% of NO3-N and 50% of TP loads were transported during April-June, and <20% of the annual loads were transported later in the growing season from July-September. Monthly NO3-N and TP loads peaked in April from the LCR but peaked in June from the SFIR; this difference was attributed to greater snowmelt runoff in the LCR. The annual NO3-N yield increased with increasing annual runoff at a similar rate in both watersheds, but the LCR watershed yielded less annual NO3-N than the SFIR for a similar annual runoff. These two watersheds are within 150 km of one another and have similar dominant agricultural systems, but differences in climate and cropping inputs affected amounts and timing of nutrient transport. © 2015. Source

Logsdon S.D.,2110 University Blvd | Malone R.W.,2110 University Blvd
Compost Science and Utilization

Compost increases water-holding capacity and total porosity. Improved soil structure may increase volume of macropores, allowing better drainage, air-exchange, and root growth. The purpose of this study was to compare water retention curves and hydraulic conductivity for packed columns with and without additions of surface compost. Columns packed with subsoil (around 60 cm long) had either compost or topsoil added to the surface. Tensiometers and hydra probes monitored soil pressure head and water content during three wetting and evaporation cycles. The columns with compost had significantly smaller bulk density at the surface than columns with topsoil (0.87 versus 1.34 g cm-3). Surface compost amendment resulted in more water when satiated (0.617 versus 0.422 m3 m-3) and at -100 cm head (0.377 versus 0.276 m3 m-3) than for topsoil at the surface, indicating a greater fraction of larger pores for the compost amended. Whole column infiltration rate was significantly faster for columns with compost than without (1.46 versus 1.11 cm min-1); however, saturated hydraulic conductivity (rate water flows through soil) on soil cores was not significantly affected by compost. Subsoil water flow and drainage was not significantly affected by surface compost. For the subsoil, in-situ column drying was significantly drier than core drainage at the wet end. There were no significant differences in whole column or surface water retention or evaporation rate. Perhaps the trend towards better water-holding capacity in the compost treatment was offset by larger pores and faster drainage, resulting in no significant difference between compost and topsoil. © 2014, Taylor and Francis Inc. All rights reserved. Source

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