Kapil Arora

Herbicide Retention by Vegetative Buffer Strips from Runoff under Natural Rainfall

Effectiveness of vegetative buffer strips for herbicide retention from agricultural runoff was evaluated in a two-year natural rainfall study. A source area of 0.41 ha (mainly Canisteo silty clay loam soil), having an average slope of 3%, was fall chisel-plowed, spring disked, and planted to corn. Three herbicides (atrazine, metolachlor, and cyanazine) were applied to the source area in each spring. Six vegetative buffer strips, 1.52 m wide ¥ 20.12 m long, were isolated with metal borders downslope of the source area in a well established bromegrass (Bromus inermis) waterway. These strips provided for three replications of two drainage to buffer area ratio treatments of 15:1 and 30:1. Herbicide retention was dependent on the antecedent moisture conditions of the strips. These retentions ranged from 11 to 100% for atrazine, 16 to 100% for metolachlor, and 8 to 100% for cyanazine. Herbicide retention by the buffer strips for the two treatments were not significantly different for the observed storm events. Herbicide concentrations in solution in outflow from the strips were less than the inflow concentrations for all the three herbicides. Infiltration was the key process for herbicide retention by the buffer strips, although there was some adsorption to in-place soil and/or vegetation. Metolachlor concentrations in sediment increased in outflow for the two treatments; however, the opposite was true for atrazine and cyanazine. Herbicide retention by sediment deposition in the strip represented about 5% of the total herbicide retention by the buffer strips. The buffer strips were found to have high percent sediment retention, ranging from 40 to 100%; thus, the strips would be more effective for retaining strongly adsorbed herbicides.

EFFECTIVENESS OF VEGETATED BUFFER STRIPS IN REDUCING PESTICIDE TRANSPORT IN SIMULATED RUNOFF

Several processes take place within vegetated buffer strips that affect their performance. To better understand these processes, a runoff study was conducted to evaluate vegetated buffer strips performance in reducing atrazine, metolachlor, and chlorpyrifos transport as affected by the drainage area to buffer strip area ratio. The simulated runoff water mixed with pesticide–treated soil was distributed onto six vegetated buffer strips, each 1.52 m wide . 20.12 m long, located downslope of the inflow distribution tank in a well established vegetated grassed waterway. These strips provided for three replications of two inflow rates designated as “drainage area/buffer strip area ratio treatments” of 15:1 and 30:1. Infiltration for the 15:1 treatment averaged 38.8% of the inflow volume, whereas it averaged 30.4% for the 30:1 treatment. Sediment retention efficiencies averaged 90.1% and 86.8% for the 15:1 and 30:1 treatments, respectively. Concentrations of atrazine and metolachlor associated with sediment outflows from the strips were larger than their respective inflow concentrations, while the results were opposite for chlorpyrifos. Concentrations in runoff water for both atrazine and metolachlor in outflow from the strips were smaller than the inflow concentrations; again, the results were opposite for chlorpyrifos. The 15:1 treatment retained an average of 52.5% of the total input of atrazine, 54.4% of metolachlor, and 83.1% of chlorpyrifos. Corresponding numbers for the 30:1 treatment were 46.8% for atrazine, 48.1% for metolachlor, and 76.9% for chlorpyrifos. Analysis of variance using the randomized block design showed that differences of percent retention of pesticide between treatments were not significant for any of the three pesticides at the 10% significance level. A lack of significant difference indicates either a need for more than three replications and/or larger area ratio treatments to be studied. The results of this study indicate that a 30:1 area ratio buffer strip could perform equally as well as a 15:1 area ratio buffer strip. Thus, less land would be required under buffer strips to get the desired results.

Teaching Farmland Drainage Design Features to Contractors and Service Providers

Abstract. Farmland drainage is an integral part of Iowa‘s landscape and plays a critical role in its bio-economy. Production capacities of Iowa soils can only be optimized with well-designed and properly operating subsurface drainage systems. Features needing attention when designing and installing a new system or retrofitting an old one include drainage intensity (spacing and depth), drainage capacity (size and grade), water quality and quantity management (controlled drainage, shallow drainage, etc.), and the economics of payback. Iowa State University Extension & Outreach initiated the Iowa Drainage School in 2007 to educate stakeholders on subsurface drainage concepts customized to the upper Midwestern states. Three hundred thirty-five participants, consisting of contractors, engineers, drainage planners, land owners, farmers, agency staff, and drainage district supervisors, have attended the school. All participants completing the end-of-school evaluation have ranked the school good (45%) or excellent (55%) and reported making drainage decisions on over 1,100 acres per participant. A summary of participants‘ preferred methods of surveying and developing topographic maps, methods of determining drainage sizing and spacing, and developing drainage maps is presented. This paper summarizes the nine-year outreach efforts of Iowa Drainage School in terms of what students learned in the school, how they have used the knowledge gained, and how they have applied what they learned in the drainage school.

Vegetative Filter Education and Assessment in the State of Iowa

Vegetative filter is one of the agricultural best management practices that helps reduce the deterioration of the surface waters. These filters use natural processes to remove a portion of the sediment and other pollutants carried by runoff before the water enters a water-body. The project aims at gathering elevation data in field-scale vegetative filters with the help of Geographic Positioning Systems (GPS) and analyzes the flow accumulation with the help of Geographic Information Systems (GIS). The overall vision and objectives for this project include (1) To determine the effectiveness of VFS by visual field observation and validation by flow mapping procedures in ArcGIS 9, (2) To compare the area ratios and percentage of flow along each stream segment at various resolutions (5X5, 10X10, 20X20 and 30X30) for different sizes of the survey data sets, (3) Compare the flow routing for USGS 7.5 Quad Angle values and spatial analysis of the elevation data at resolution of 30X30. This study is of great significance in regard to key water quality and surface runoff issues, which are gaining broad awareness while developing consciousness about effective management practices and good land stewardship values. This paper will present the data and results for this study, which is still on going.