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Site-Specific Evaluation of a Claypan Soil with Subsurface
Drainage-Impact on Corn Grain Yield

Final Report 2001

Kelly A. Nelson, D. Kent Shannon,
Allen L. Thompson, and Stephen H. Anderson


ABSTRACT

A field experiment was designed to evaluate the impact of subsurface drainage compared with no drainage on corn grain yield using precision agriculture technology. Subsurface drain tiles were installed on 50 ft spacings. Gate valves were installed in existing drain tiles for a non-drained control. The harvested corn population was not affected by drainage treatments in 2001. Depth to the water table 7 and 15 ft from the open drain tile was 4 to 8 inches deeper than plugged drain tiles. Soil temperature 12 ft from the drain tile was 0 to 4 F warmer for drained soil through the day than non-drained soil. Corn plants above open drain tile lines had greater tissue nitrogen levels than plants 25 ft from the subsurface drain tile. Corn grain yield above open drain tiles averaged 13 bu/a greater than 25 ft from the drain tiles. A fifty foot drain tile spacing was too wide for claypan soils. A combination of warmer soils during early plant growth and a lowered water table during heavy rainfall events may have contributed to increased grain yield above the drain tile compared with between drain tiles.

BACKGROUND

Farmers with flat claypan soils have used improved varieties, soil fertility, conservation tillage, narrow-rows, weed management, insect resistant cultivars, and nematode and disease tolerant cultivars to increase productivity and profitability. However, water management is still one of the major limiting factors affecting productivity of these soils. Claypan soils are often wet and cold in the spring which reduces crop stands, encourages disease, delays planting dates, and results in sub-optimal planting conditions. Subsurface drainage is uncommon in claypan soils because of the soil properties affecting internal drainage. The clay subsoil restricts downward movement of water, reduces natural drainage, and results in a high water table due to its slow permeability. A perched seasonal water table is common from November to May and can range from 0.5 to 1.5 ft from the soil surface (Watson, 1984). In addition, wet fall weather conditions often prevent timely harvesting and cause puddling of the soil during harvest which results in soil compaction. Therefore, drain tiles installed at the interface between the claypan and topsoil may be beneficial.

Site-specific research evaluating the correlation between crop productivity and soil electrical conductivity of claypan soils reported that areas in fields with poor drainage had a larger effect on yield compared to other soil properties (Kitchen et al, 1999). Previous claypan drainage research with a drain spacing of 20 ft reported drainage alone increased corn and soybean grain yield (Sipp et al, 1986). In other research, drainage used in conjunction with subirrigation increased alfalfa yield three fold compared to non-irrigated treatments, but approximately 15 ft tile spacing was recommended (Rausch et al, 1990). Several producers have recognized the need for drainage of flat claypan soils; however, tile and installation costs are the major factors affecting the adoption of subsurface drainage. Therefore, tilers may recommend wider than necessary spacings between laterals to help producers save cost.

Limited research has evaluated the benefits of tile drainage of claypan soils while no research has evaluated yield response of commercially installed drain tile into claypan soils or the benefits and production variability of drained compared with non-drained claypan soils on a large scale. This research utilized integrated systems research to evaluate the impact of tile drainage of claypan soils on corn grain yield. The objectives of this research were to determine: 1) the suitability of claypan soils for subsurface drainage using precision farming technology, 2) crop variability and productivity of subsurface drained compared with non-drained claypan soils, and 3) the economic benefit of claypan soils with drainage compared to soils without drainage.

METHODS

A research site was established on the Keller Farm in Marion Co. during the 2001 growing season. This research was arranged as a completely randomized design with two treatments (drained and non-drained) and three replications. Drained plots had open tile lines while non-drained plots had Valterra gate valves installed in the drain tile line with a rubber seep collar around the drain tile to prevent water movement around the gate valve. Plots were 50 by 700 ft. Subsurface drain tile was commercially installed approximately 30 in deep on 50 ft centers in August, 2000. The claypan was approximately 2.0 ft deep at the research site. The field was deep ripped 12 to 18 in deep two times in the fall and field cultivated in the spring. Soil was a Putnam silt loam (14% sand, 74% silt, 12% clay surface soil texture) with 2.4% organic matter and pH 6.8. The site was fertilized with hog manure and soil tests indicated high levels of P (50 lb/a) and K (303 lb/a). Corn was planted April 19 at 30,000 seeds/acre in 30 in wide-rows. The site was side-dressed with 50 lb/a N and tissue samples were collected during silking.

Observation wells, constructed out of slotted PVC pipe, were installed in Mid-May to monitor the water table depth during the growing season 7, 15, and 25 ft from the drain tiles. Observation were installed 12 in below the claypan depth and extended 18 in above the soil surface. Water-table levels in the observation wells were monitored weekly. Soil temperature sensors were buried two inches deep in each plot 12.5 ft from the drain tile. The location of tile lines, soil grid samples, observation wells, temperature sensors, were recorded with a portable GPS unit and a handheld computer. Crop grain yield and final stand within each treatment were measured using a yield monitoring system to obtain data for yield maps.

RESULTS:

Precision harvesting technology indicated grain variability within subsurface drained and non-drained plots (Figure 1). Grain yield above subsurface drain tiles averaged 13 bu/acre greater than 25 ft from the drain tiles (Figure 2). Open drain tiles had less variability above the drain tile than 25 ft from the drain tile. An increase in grain yield was related to improved drainage and tillage caused by drain tile installation equipment. However, grain yield above the plugged drain tile averaged 14 bu/a greater than 13 or 25 ft from the tile.

Corn stand was not affected by drainage (Figure 3). Final stand is one of the primary factors affecting grain yield. Young plants are more susceptible to standing water than mature plants. Rainfall events in 2001 were delayed and the corn stand was not affected by saturated conditions. However, a perched water table during a rainy period in early May probably had a large influence on grain yield between the drained and non-drained treatments. Depth to the water table on May 9th seven and 15 ft from the open drain tile was four to eight inches deeper than plugged drain tiles (Figure 4). Tissue analysis indicated corn plants above the drain tiles had higher nitrogen levels than plants 25 ft from the subsurface drain tile (Figure 5). Plants above the open drain tiles may have greater nitrogen use efficiency than plants between the drain tiles which could increase yield. However, plants above open drain tiles may have luxury nitrogen consumption compared to plants between the drain tiles.

Soil temperature of drained soils was expected to warm faster than non-drained soil. Temperature at a two inch depth indicated soil 12 ft from the drain tile was up to 4 F warmer than non-drained soil (Figure 6). The May 17 date was selected as an illustration date because it was four days after a 1.4 in rain. Drained soils were often 0 to 4 F warmer through the day (800 to 1900 h) than non-drained soil; however, drained soils were 0 to 1 F cooler than non-drained soils through the night (1900 to 800 h) (data not presented). This was probably related to the amount of sunlight present on a given day and the timing of a rainfall event. Temperature differences through the day were probably related to the cooling effect of evaporation from the soil surface.

Finally, this research indicates a fifty foot drain tile spacing was too wide for claypan soils. This agrees with computer simulation conclusions by Mostaghimi et al (1985) and visual assessments by Rausch et al (1990). Installation cost for 50 ft drain tile has been estimated at $400/acre. A minimum average grain yield increase of 20 bu/acre at $2.00/bu is needed for a 10-year loan (personal communication with a local loan officer). The field average for the drainage system on 50 ft centers averaged 5 bu/acre greater than the non-drained area excluding the grain yield above the drain tile for the non-drained area. However, the long-term impact of drainage on the internal soil properties of claypan soils can not be estimated after one year of research. Additional research needs to monitor grain yields over time at such sites to help farmers make informed decisions regarding drainage and perfect drainage systems.

ACKNOWLEDGEMENTS

We would like to extend our sincere thanks to Chuck and C.B. Keller for their cooperation in this research. A special thanks is extended to Dana Harder, Scott Drummond, and MattVolkmann for their technical assistance.

REFERENCES

Kitchen, N.R., K.A. Sudduth, and S.T. Drummond. 1999. Soil electrical conductivity as a crop productivity measure for claypan soils. J. Prod. Agric. 12:607-617.

Mostaghimi, S., W.D. Lembke, and C.W. Boast. 1985. Controlled-drainage/subirrigation simulation for a claypan soil. Trans. ASAE 28(5):1557-1563.

Rausch, D.L, C.J. Nelson, and J.H. Coutts. 1990. Water management of a claypan soil. Trans. ASAE 33(1):111-117.

Sipp, S.K., W.D. Lembke, C.W. Boast, J.H. Peverly, M.D. Thorne, and P.N. Walker. 1986. Water management of corn and soybeans on a claypan soil. Trans. ASAE 29(3):780-784.

Watson, F.C. 1984. Soil Survey of Marion and Ralls Counties, Missouri. USDA-SCS. pp. 117.


Figure 1. Corn grain yield as affected by drainage.
Corn Grain Yield


Figure 2. Corn grain yield 7, 15, and 25 ft from the drain tile of drained (open tile lines) and non-drained (plugged tile lines) treatments. Vertical bars indicate grain yield variability measured as the standard deviation.
Corn Grain Yield


Figure 3. Corn population at harvest 7, 15, and 25 ft from the drain tile of drained (open tile lines) and non-drained (plugged tile lines) treatments. Vertical bars indicate population variability measured as the standard deviation.
Corn population at harvest
Figure 4. Depth to the water table 7, 15, and 25 ft from the drain tile for drained (open tile lines) and non-drained (plugged tile lines) treatments on May 9. Vertical bars indicate population variability measured as the standard deviation.
Depth to the water table


Figure 5. Corn leaf tissue analysis for nitrogen. Leaves were harvested from plants above an open drain tile and 25 ft from an open drain tile.
 Corn leaf tissue analysis for nitrogen


Figure 6. May 7, 2001 soil temperature of drained and non-drained soil two inches below the soil surface. Data points with asterisk symbols were significant at p<0.05.
May 7, 2001 soil temperature

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