MU Drainage and Subirrigation (MUDS) Research Update
December 2006

Kelly A. Nelson and Randall L. Smoot
University of Missouri Greenley Research Center
660-739-4410, nelsonke@missouri.edu

Background:
Economic situations have caused several Missouri farmers to re-evaluate production systems that maximize yield and maintain environmental sustainability. Agricultural drainage is not a new concept; however, utilizing drainage as part of an integrated water management system (IWMS) is a relatively new concept that has been shown to improve water quality and sustain agricultural viability. Subsurface drainage water from agricultural lands contributes to the quantity and quality of water in receiving streams when properly implemented water management systems are adopted.

Upland, flat claypan soils commonly have a seasonal perched water table from November to May, which is caused by an impermeable underlying clay layer that restricts internal drainage. Research in other states has reported increased crop production using IWMS's that incorporate subsurface drainage and subirrigation. The MUDS research program was initiated to determine the suitability of claypan soils for drainage and a drainage/subirrigation (DSI) water-table management system, and to evaluate the effect of the systems on corn and soybean grain yield at different drain tile spacings compared to non-drained claypan soil.

Methods:
Subsurface drainage and DSI water-table management systems were installed in July, 2001. This research was arranged as a split-plot design with two main plots (drainage and drainage/subirrigation systems) and a factorial arrangement of sub-plots including a non-drained control and three drain tile spacings (20, 30, and 40 ft) and two crops (corn and soybean) with four replications. The corn and soybean plot size was 60 to 80 by 150 ft depending on the drain tile spacing. Soil was a Putnam silt loam with 10%, 75%, and 15% sand, silt, and clay, respectively. Field information and rainfall data are summarized in Tables 1 and 2, respectively. A delayed planting control was included in the design. Non-drained checks usually delay planting of drained treatments in research projects; therefore, two non-drained controls were included in the design. One is planted at the time the drained treatments are planted regardless of the soil conditions. The other is delayed based on typical soil conditions that are suitable for planting.

The DSI system was shifted into controlled drainage mode in June, 2002 and a temporary water supply system was implemented for subirrigation during the growing season. The water supply did not provide enough volume to substantially raise the water table; however, baseline data were established on the impact of subirrigation on production in 2002. These results have been similar to subsequent years and were included in the results. Soybean plots equipped with a water-table management system were not subirrigated in 2002. Subirrigation of soybean was initiated in 2003 and corn was subirrigated from 2004 to the present. Table 1 summarizes the subirrigation timing schedule while Table 2 summarizes the amount of water supplied through the subirrigation system on the 20 ft lateral spacing from 2004 to 2006. Water meters recorded the quantity of water supplied through the subirrigation system. This was converted to inch equivalents of rainfall.

Additional research was initiated in 2004 and 2005 to evaluate the use of slow-release nitrogen fertilizer (ESN, Agrium, Alberta, Canada) applied to corn to control nitrogen loss when there were differences in soil moisture conditions and drainage. Since there was no delay in early planted corn in 2002 and 2003, an overhead irrigation system was installed to replace this treatment. Corn was irrigated according to the Woodruff irrigation scheduling chart. The amount of water applied with the overhead irrigation system was reported in Table 2. Sub-plots included coated (ESN) and non-coated urea at 0, 125, and 250 lb N/a. Crop performance has been evaluated above and between drain tiles over the past five years; however, data was not presented in this report.

Corn research in 2006 compared the relative corn growth response and environmental N losses after application of different N fertilizer sources under a range of soil moisture conditions imposed by drainage and irrigation, and examined the spatial differences in soil N transformations and N losses during the growing season between drainage and subirrigation tile lines. Preplant injected anhydrous ammonia, urea ammonium nitrate, urea, or polymer coated urea applied at 150 lbs N/acre were incorporated following application.

Results:
2002 Rainfall during the growing season was sufficient in some areas in Northeast Missouri and insufficient in others. Corn planting date was not delayed by wet conditions; however, the crop experienced excessive rainfall from April 16 to May 13 (Table 2) and cool temperatures (data not presented). Rainfall was scattered and a total of 3.4 inches of rain was recorded from June 24 to August 24.

Corn grain yield for the non-treated control was 62 to 63 bu/acre (Table 3). Drainage only (DO) treatments increased corn grain yield 10 to 20 bu/acre depending on the drain tile spacing. The drainage/subirrigation treatment (DSI) with a 20 ft lateral spacing increased grain yield two fold compared to the non-drained control and was 10 bu/a greater than the DSI treatment with a 30 ft lateral spacing. Even though grain yield was doubled with the DSI system, the potential for the system was probably underestimated due to an inadequate water supply. Corn grain yield above the drain tile with subirrigation ranged from 150 to 165 bu/a depending on the treatment (data not presented).

Soybean was planted three days earlier in the subsurface drained compared to the non-drained, delayed planting control (Table 1). Soybean grain yield was 8 to 10 bu/a greater with subsurface drainage when compared to the non-drained and non-drained delayed planting treatments (Table 4).

2003 Rainfall was adequate until mid-August. Early planted corn was not delayed by wet conditions; however, the corn crop experienced excessive rainfall from mid-April to mid-May (Table 2) and cool temperatures (data not presented). Rainfall was scattered and a total of 0.1 in. of rain was recorded from August 3 to August 25 with above average temperatures (data not presented).

Corn grain yield for the non-drained controls was 99 to 109 bu/acre in 2003 (Table 3) while drainage only increased corn grain yield 22 to 37 bu/acre depending on the drain tile spacing.

Soybean was planted two days earlier in subsurface drained treatments when compared with the non-drained control (Table 1). Soybean grain yield was 6 to 8 bu/a greater with subsurface drainage than the non-drained and non-drained delayed planting treatments (Table 4). Soybean grain yield was similar in the drained and subirrigated treatments. Late rains probably helped increase seed fill and test weight. An earlier subirrigation timing may be necessary to maximize soybean grain yields.

2004 In general, dryland corn and soybean grain yields were above average in Northeast Missouri. Rainfall was consistent throughout the spring and summer; however, excessive rainfall in the fall hindered harvest (Table 2). Harvesting during these conditions probably contributed to increased compaction. An additional 5.6 inches of water was recommended and applied according to the Woodruff chart during the season. However, only 0.33 inches of water were applied through the subirrigation system on the 20 ft drain tile spacing.

Drainage only increased corn grain yield up from 20 to 49 bu/acre depending on the N treatment, N rate, and drain tile spacing. All 20 ft drain tile spacings increased grain yield regardless of N rate or source when compared with the non-treated control. Corn grain yield was increased up to 36 bu/acre with DSI depending on the N source, N rate, and drain tile spacing. Drainage only or DSI increased grain yield up from 19 to 49 bu/acre when compared to overhead irrigation alone. Differences in corn grain yield response were probably related to denitrification differences due to N source and soil moisture differences among treatments.

Soybean planting date was delayed 17 days in the non-drained control compared to drained treatments due to wet soil conditions (Table 1). Soybean planted in the non-drained control at the same time drained treatments were planted had grain yields 12 bu/a greater than the delayed planting control (Table 3). Soybean grain yield was 12 to 27 bu/a greater with DO and DSI regardless of drain tile spacing when compared to the non-drained controls.

2005 Rainfall was below normal with a total of 11.6 inches throughout the growing season (Table 2). Less than 4 inches of rainfall was recorded from mid-June to early September. Variability between drainage tiles for the DSI treatment was evident in corn and soybean (visual observation). Twospotted spider mites (Tetranychus urticae) were widespread in non-irrigated treatments during the first week of August (Figure 3). The entire plot area was sprayed to min to minimize a possible confounding effect of insect feeding on soybean grain yield. A dry fall allowed for an efficient harvest and optimal weather for fall tillage.

The non-treated control corn grain yield was 28 to 40 bu/a (Table 3). Low rainfall, high air temperature, and wind during pollination of corn helped reduced grain yields (data not presented). Drainage only increased corn grain yield 1.7 to 2.8 fold when compared with the non-drained control. DSI increased grain yield from 3 to 5 times greater than the non-drained control. Finally, grain yield with overhead irrigation was 6 to 9 times greater than the non-drained control. The degree of impact of water management systems on corn grain yield was affected by N rate and source. Drought stress differences above and between the drainage tiles for the DSI system were evident and grain yields were quantified above and between the drainage tiles. Corn grain yield above the drain tile with subirrigation ranged from 160 to 190 bu/a depending on the drain tile spacing (data not presented).

There was no delay in soybean planting date due to wet soil conditions. Soybean yield increased 7 bu/a with drainage only on a 20 ft spacing compared with the non-drained control (Table 4). DSI increased grain yield 9 to 16 bu/a depending on the drain tile spacing. Soybean above the drain tiles in the drainage/subirrigation water management treatment matured earlier and had complete leaf senescence before soybean between the drain tiles and non-drained soybean.

2006 Precipitation following planting was limited, but sufficient for adequate germination and early growth (Table 2). Irrigation was needed in late June until the first week of August and again in late August. Overhead irrigation required over six times more water than subirrigation throughout the season. Another dry fall allowed timely harvest and tillage operations.

The corn hybrid was switched to 'DK C61-68' (Table 1). Dry conditions following pollination reduced grain yields of non-irrigated treatments. All of the water table management treatments responded to N applications regardless of N source in 2006 (Table 3). The non-drained control and drainage only treatments had similar grain yields which was probably due to a relatively dry spring. DSI on 20 ft lateral spacings increased yield 41 to 72 bu/acre when compared to the non-drained control with similar N sources. Subirrigated corn with ESN had grain yields similar to overhead irrigation. Crop response to the water-table management system was ranked overhead irrigation > DSI > drainage only = non-drained.

Soybean planting date was delayed 4 days for the non-drained control when compared with drained treatments (Table 1). Drainage only or DSI increased soybean yield 3 to 5 bu/acre when compared to the non-drained delayed planting control (Table 4). No differences in yield among drain tiles spacings were observed.

Summary:

• Drainage only increased average corn grain yields up to 15% while DSI has increased average yields up to 58% when compared with non-drained, non-irrigated soil (Table 3).
• Overhead irrigation increased grain yield 25% compared to subirrigated corn with 20 ft laterals when averaged over all N treatments in 2004, 2005, and 2006 (Table 3). However, applied water was on average 8.5 times greater for overhead irrigated corn compared with subirrigated corn on a 20 ft drain tile spacing during this period (Table 2).
• Soybean planting date was delayed an average of 4 days for the non-drained control when compared with drained soils from 2002 to 2006 (Table 1).
• Soybean grain yield with DO has averaged 17 to 23% greater than the non-drained or non-drained delayed planting controls (Table 4). Similarly, DSI had soybean grain yields 21 to 26% greater than the non-drained or non-drained delayed planting controls.

Acknowledgments:
The authors would like to thank the Missouri Soybean Merchandising Council; Missouri Corn Growers Association; Landmark Irrigation, Inc., Taylor, MO; Agri Drain Corp., Adair, IA; Hawkeye Tile Inc., Taylor, MO; Liebrecht Manufacturing, Continental, OH; Timewell Tile, Timewell, IL; IMI Equipment, Kahoka, MO; BASF; Syngenta; Monsanto; Pioneer Hi-Bred; and Kruger Seeds for their support. In addition, a special thanks is extended to Matthew Jones, Dana Harder, Chris Bliefert, and Ben Bradley for their technical assistance.

Table 1. Field information and selected management practices for corn and soybean from 2002 to 2006.

Table 2. MUDS annual rainfall, overhead irrigation, and subirrigation totals for 2002 to 2006.

Table 3. Corn grain yield for the non-drained, drainage only, and drainage/subirrigation water-table management treatments at 20, 30, and 40 ft lateral spacings from 2002 to 2006.^a.

Table 4. Soybean grain yield for non-drained, drainage only, and drainage/subirrigation water-table management treatments at 20, 30, and 40 ft lateral spacings from 2002 to 2006.