Drainage Research to Improve Runoff Water Quality and Soil Trafficability
by Ted S. Kornecki, James L. Fouss, Brandon C. Grigg and Lloyd M. Southwick
In recent years there has been increasing concern about the quality of runoff waters from sugarcane fields. This concern encompasses not only streams, rivers, lakes, and groundwater, but also wetland areas adjacent to and/or downstream from agricultural lands. A new USDA-Agricultural Research Service (ARS) field research/ demonstration project has been initiated in the Lower Mississippi River Valley (LMRV) to quantify the potential beneficial effects of water table control in reducing runoff, and the associated reduction in losses of sediment and agrochemicals (fertilizer and pesticide) carried in the runoff. Further, the research will demonstrate to sugarcane growers the benefits of improved trafficability when the cane harvest season is excessively wet, which typically occurs about every 5 to 6 years in the LMRV. Both subsurface drainage conduit and parallel field drainage ditch systems will be considered in formulating recommendations.
Many farmers in the LMRV do not appear to be aware of the multiple benefits of subsurface drainage. These benefits include increased crop yields, cane stubble longevity, and improved trafficability for planting, cultivation, pest management, and harvesting operations. For those farmers familiar with the practice, most are reluctant to install subsurface drainage because of the high initial cost to install the systems. A typical system may cost $450/acre to install. The improved crop production efficiency and yield increases provided by subsurface drainage will typically offset the installation cost in 3 to 5 years for sugarcane production. Complicating this situation is the fact that most lands (90%) used for sugarcane production are rented or leased, and improvements on the land (such as subsurface drainage) are not typically paid by the land owners; these costs must generally be paid by the grower. Additionally, the marketing infrastructure for sugarcane provides that the sugar mills receive a contract percentage of the selling price for the sugar produced, but the mills do not typically share in the cost of production related to land improvements (such as subsurface drainage). The costs for purchasing and maintaining the farming equipment, including the harvesting machines, are typically paid by the sugarcane grower.
From 1993 to 2000, the percentage of Louisiana sugarcane harvested with a modern chopper harvester (Cane Combine) increased from 0 to 75%, and in the next few years 100% of the cane may be harvested by the chopper harvester. The change from the soldier harvester system is being brought about by the development of high yielding, usually lodged, cultivars and by pending restrictions on burning cane. Improved trafficability for operation of modern cane combine and transport equipment in sugarcane production harvesting operations during wet seasons will likely be a major future benefit provided to the grower by water table control (e.g. subsurface drainage). Improvements in stand longevity, such as a 6-year cane cycle (rather than the current 4-year cycle for plowing out and replanting cane) and higher sugarcane yields, should increase overall profitability of sugarcane production for the grower.
Project Objectives and Considerations
Site Characterization and Plot Design
Description of Research and Demonstration Site
The research plan also includes procedures to develop techniques for measurement of trafficability parameters in terms of soil physical properties related to soil strength and soil moisture. This research phase will also involve field experimentation, laboratory investigation, modeling and simulation methods.
For plots with laser installed subsurface drainage at 0.2 % grade, two different water table levels as treatments will be chosen to study the effects of a future residue management on water quality and trafficability.
Surface runoff from sugarcane fields up-slope from the experimental site has been diverted into subsurface culvert pipes to route it around the site and to discharge it to a surface outlet downslope from the site. A National Weather Service Class-A automated weather station is located approximately 490 ft from the experiment site. Meteorological data (e.g., rainfall, air temperature, soil temperature, relative humidity, pan evaporation, wind speed and direction, and total radiation) from the weather stations automatic data-logger will be used in conjunction with the study. Evapotranspiration (ET) will be estimated from pan evaporation and the modified Penman equation.
The 4-inch diameter corrugated plastic tubing for the project was donated by the Plastic Pipe Institute-Corrugated Polyethylene Pipe Association (PPI/CPPA), Washington, D.C. The member company of PPI/CPPA selected by PPI to donate the pipe for St. Gabriel project was Advanced Drainage Systems, Inc., Columbus, Ohio. The drainage contractor awarded the competitive contract to install the drain pipes was Luttrell & Sons Drainage, Inc., Dundee, Kentucky.
The water table depth (WTD) at the mid-point between drainlines in the experimental area of each plot, or at the plot-center in the surfaced drained only plots, will be monitored with an in-situ manometer-type sensor. This WTD monitoring system consists of a short section of perforated pipe, buried at the plot-center or mid-point between drains, that is connected via a small-diameter unperforated tube that extends to a WT riser-pipe located at the plot border near the drainage sump or runoff sampling equipment. An electrical water level sensor will be used in each riser-pipe to measure WTD vs. time via an electronic data-logger system.
Sugarcane variety LCP85-384 widely used in Louisiana was planted (August, 2000) parallel to subsurface drainlines and to surface drainage ditches for surface drainage only plots.
Sampling and Measurements Procedure
The surface drainage runoff samplers acquired for the project were model 900MAX, American Sigma, Inc., Loveland, Colorado. The runoff flumes fabricated to the project engineers design by Corrosion Control Systems, Inc., Medina, New York.
Surface runoff measurement and sampling systems (flumes and automatic samplers) will be installed by the summer of 2001. The new St. Gabriel research site will be fully operational and automatic data collection begins by the fall of 2001. L&W
Mention of the trade or manufacturer names is provided for information only and does not constitute endorsment by USDA-ARS.
For more information, contact Dr. Ted S. Kornecki, USDA-ARS, Mid South Area, Soil and Water Research Unit, 4115 Gourrier Ave., Baton Rouge, LA 70808, (225)578-0745, fax (225)289-0327, firstname.lastname@example.org.
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