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Effect of tillage and water table control on evapotranspiration, surface runoff, tile drainage and soil water content under maize on a clay loam soil
Agricultural Water Management 54 (2002) 173±188
Effect of tillage and water table control on evapotranspiration, surface runoff, tile drainage and soil water content under maize on a clay loam soil C.S. Tan*, C.F. Drury, J.D. Gaynor, T.W. Welacky, W.D. Reynolds Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Center, 2585 Highway 20, E., Harrow, Ont., Canada N0R 1G0 Accepted 26 September 2001
Abstract Two tillage and two water table control treatments under continuous maize cropping were evaluated over a 3-year period (1992±1994) for their effects on evapotranspiration, surface runoff (SR), tile drainage (TD) and soil water content in the root-zone on a clay loam soil in southern Ontario. The tillage treatments included soil saver (SS, reduced tillage) and moldboard plow (MP, conventional tillage). The water table control treatments included controlled drainage-subirrigation (CDS) and regular tile drainage (DR). There was no signi®cant difference (P < 0:05) in evapotranspiration estimates between the SS and MP tillage treatments. The SS tillage increased SR compared with MP tillage during the non-cropping periods in 1993 and 1994, but not in 1992. Relative to MP, the SS tillage increased soil pro®le water content during the cropping period but decreased soil pro®le water content during the non-cropping period in 1992. The CDS treatment produced signi®cantly higher (P < 0:05) evapotranspiration and soil water content than the drainage treatment during the dry 1993 and 1994 years, but not during the wet 1992 year. The CDS treatment also had signi®cantly lower (P < 0:05) TD and higher SR than the drainage treatment. For all the treatments, over 65% of SR and TD occurred in the 5 month non-cropping period from November to March. Of the total annual water input (precipitation and/or subirrigation) to the ®eld site, 8% was partitioned to SR, 30% was partitioned to TD, 55% was removed by crop and soil evapotranspiration and 7% was accounted for by changes in soil pro®le water content. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Tillage; Controlled drainage/subirrigation; Evapotranspiration; Runoff; Tile drainage; Soil pro®le water content * Corresponding author. Tel.: 1-519-738-2251x475; fax: 1-519-738-2929. E-mail address: [email protected] (C.S. Tan).
0378-3774/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 1 ) 0 0 1 7 8 - 0
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1. Introduction One of main challenges to agriculture on fine-textured soils is managing the amount and temporal distribution of soil water in the crop root-zone. Too much water may result in insufficient root-zone aeration and it may also impede or prevent critical tillage, planting and harvesting operations (Drury et al., 1999). Too little soil water, on the other hand, may cause crop drought stress and subsequent yield reduction (Drury and Tan, 1995; Tan et al., 1993). Tillage type, cropping practices and water table management can have substantial effects on the amount and temporal distribution of root-zone soil water through their impacts on SR, TD and crop evapotranspiration (Bryant et al., 1987; Van Vliet et al., 1993). It is well established, for example, that no-tillage in wet temperate climates can reduce SR (Lee and Nielsen, 1987), but this can also increase infiltration and subsequent tile drainage (Tan et al., 1998). The mechanism by which this occurs is not well understood, however, and it is likely to vary with physiography, soil type, climate and the duration of no-tillage (Baker, 1987). The type of crop and/or crop rotation can also affect root-zone soil water by influencing the partitioning of water amongst runoff, evapotranspiration and infiltration (Bryant et al., 1987). The shallow and closely spaced tile drainage systems usually found in the fine-textured soils of southwestern Ontario are designed to permanently remove excess water as quickly as possible during the spring and fall so that root-zone aeration and agronomic operations are not impeded. Although these systems perform this function rather well, in doing so they may also reduce soil water storage and thereby indirectly contribute to root-zone soil water deficits during the growing season when precipitation is low and evapotranspiration is high. In this regard, attachment of water table control structures to existing tile drainage systems has met with some success at reducing root-zone soil water deficits in fine-textured soils, but this appears to be only a partial solution (Tan et al., 1993). What is needed for fine-textured soils in wet temperate regions, such as southwestern Ontario are water/soil/crop management strategies that can quickly remove excess soil water, but also maximize and/or replenish soil water for crop use during times of growing season water deficit. As an initial step toward this overall goal, the objective of this study was to use a water balance approach to elucidate the impacts of two tillage systems (MP, SS) and controlled drainage with subsurface irrigation on evapotranspiration, SR, and change in soil profile water content under maize (Zea mays L.) grown on a clay loam soil in southwestern Ontario. 2. Materials and methods 2.1. Site description The study included two tillage and two water management treatments, replicated four times, on sixteen 15 m wide by 67 m long field plots (Tan et al., 1993; Drury et al., 1996). The two tillage treatments were moldboard plow (MP, conventional tillage) and soil saver (SS, reduced tillage). The two water management treatments were regular
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drainage (DR) only and controlled tile drainage with subsurface irrigation (controlled drainage-subirrigation, CDS). The site is located on poorly drained Brookston clay loam soil (Typic Argiaquoll) which is the dominant soil type in Essex County, Ontario, comprising over 80% of the agricultural land. The Ap horizon is a dark brown, clay loam 30 cm deep with 1.5% organic carbon. The B horizon has a clay texture to a depth of 1.5 m. Each of the 16 field plots was hydraulically isolated and had two 104 mm diameter tile lines at 7.5 m spacing and an average depth of 0.6 m. The water table was maintained at 30 cm below ground level in the CDS treatments through the use of tile outflow risers and subirrigation during the growing season (Tan et al., 1993). The risers were removed briefly in the spring and fall to allow planting and harvesting, then reinstalled after harvest to maintain the water table at 30 cm depth for the winter and spring periods. No drainage control or subirrigation occurred in the DR treatments. 2.2. Agronomy The MP plots were plowed to a depth of 15 cm in the fall and disced in the spring for seedbed preparation. The SS plots were prepared in the fall with a Glencoe soil saver implement (Model F551-A, series 3, Glencoe, Farmhand Div, Excelsior, MN) equipped with seven 35 cm sweeps at 38 cm spacing which disturbed the soil to a depth of 15 cm. No spring seed bed preparation was performed in the SS plots before planting. A four row Kinze (Kinze Manufacturing Co., Williamsburg, IA) planter seeded maize (Zea mays L., Pioneer 3573) at 65,000 seeds ha±1 in 75 cm wide rows. Fertilizer (8-32-16) was band applied beside the seed at a rate of 132 kg ha 1. A brush applicator applied urea (46-0-0) at the six-leaf stage at a rate based on the average nitrate soil test and previous crop history (Drury et al., 1996). Atrazine (6-chloro-N-ethyl-N0 -(1-methylethyl)-1,3,5-triazine2,4-diamine), metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin5(4H)-one) and metolachlor (2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-methoxy-1methylethyl) acetamide) were banded over the maize row immediately after planting to control weeds. 2.3. Surface runoff and TD measurements Surface runoff (SR) and TD water from the 16 experimental plots was routed to a central instrumentation building and collected in 32 polyethylene sumps (500 mm diameter by 750 mm deep). Each sump was equipped with an electrical, float activated, effluent pump. SR and TD from each individual plot flowing into the respective sumps were pumped through water metres to an outlet drain. A multi-channel datalogger utilized the analog signal of the water meters to monitor, measure and store water volume data on a continuous basis (Soultani et al., 1993). 2.4. Soil profile water content Soil profile water content was monitored using a subsurface neutron moisture probe (model CPN 503). Three aluminum access tubes were inserted to a depth of 120 cm in
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each plot. The measurements were taken three times per week at 20 cm intervals from 0 to 100 cm depth during the growing season. The neutron probe was calibrated against gravimetric sampling using, yv 0:163R/Rw 0:026 (r 2 0:984 and Syx 0:012), where yv is the volumetric soil water content (m3 m 3), R the neutron meter count rate in the soil and Rw the standard meter count rate in the shield. As there is little evidence of maize root growth below 80 cm in this poorly drained clayey soil (Stone et al., 1987), the volumetric soil water content obtained by the neutron probe was converted to soil moisture (SM) in the top 800 mm of soil depth using, SM yv 800 (mm). 2.5. Meteorological measurement Weather data were recorded within 0.5 km of the experimental site. These measurements included air temperature, solar radiation, rainfall, wind speed and direction and relative humidity. 2.6. Estimating evapotranspiration and change in soil profile water content The water balance can be used as a means for measuring evapotranspiration (ET) during the cropping period (April±October) using: ETt
t X
Pd Id
SRd
TDd
DWCd
(1)
d1
where, DWCd SMd
SMd
(2)
1
and ET is evapotranspiration (mm), P the precipitation (mm), I the subirrigation amount (mm), SR the surface runoff (mm), TD the tile drainage (mm), DWC the change in soil pro®le water content in the 0±80 cm depth (mm), t the number of days over which the evapotranspiration and change in soil pro®le water content are calculated, d the day (d 1; 2; 3; . . . ; t) and SMd and SMd 1 are the soil water content in the 0±80 cm depth (mm) on days d and d 1, respectively. The P, SR and TD are measured continuously all year. Subirrigation water was applied only during summer (June±September) on an as needed basis and was accurately measured using a water meter. The change in soil pro®le water content P in the 0±80 cm depth during summer (DWCt) was calculated using, DWCt td1 SMd SMd 1 with SMd and SMd 1 measured using the neutron moisture probe. A positive DWC value indicates a net increase in soil pro®le water content, while a negative DWC value indicates a net decrease. As shown in Table 20 of Treidl (1979), potential ET is effectively zero in our climate region during the noncropping period (November±March). Hence, the change in soil pro®le water content during the winter (DWCt) can be calculated using: DWCt
t X Pd
SRd
TDd
(3)
d1
Deep drainage and/or recharge from below the 80 cm depth could introduce error into
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Eqs. (1)±(3). Inspection of the pro®le soil water content between 80 and 100 cm depth indicated, however that only very small hydraulic gradients existed in this depth range. In addition, the saturated hydraulic conductivity below 80 cm was very low at <4.6 cm per day. Consequently, deep drainage and recharge from below 80 cm depth were negligible in this study. 3. Results 3.1. Precipitation and subirrigation amount The monthly precipitation for the three experimental years and the corresponding 48 year averages are shown in Table 1. During 1992, total annual precipitation was 98.6 mm above the 48 year mean and cropping season precipitation (April±November), was 87 mm above the 48 year mean. Both 1993 and 1994 years were dry with total precipitation of 180.9 and 165.6 mm below the 48 year mean, respectively (Table 1). For all 3 years, subsurface irrigation for the CDS treatments was initiated during the first week of June and terminated at the end of August. As the 1992 cropping season was wet, only 5.7 mm of water was applied to the CDS treatments during that year. On the other hand, the CDS treatments received 126 and 115 mm of subsurface irrigation water in 1993 and 1994, respectively, owing to low growing season rainfall in those years. 3.2. Soil profile water The soil profile water in the 0±80 cm depth during the growing season was similar between the MP and SS tillages for all 3 years (Fig. 1). However, the soil profile water in Table 1 Monthly field site precipitation (mm) in 1992, 1993, 1994 and 48 year average Month
January February March April May June July August September October November December Total
Precipitation (mm) 1992
1993
1994
48 year average
33.5 44.0 65.0 91.5 52.5 67.0 118.0 129.0 133.5 50.0 129.5 54.0 967.5
94.0 8.0 41.0 81.0 50.0 108.5 47.5 29.0 107.0 52.0 49.5 20.5 688.0
73.8 40.8 52.5 74.5 47.3 83.3 31.0 111.3 32.3 61.5 56.5 38.5 703.3
51.7 44.8 67.7 80.0 73.3 95.8 85.5 82.5 83.1 54.3 73.1 77.1 868.9
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Fig. 1. Total soil profile water content (mm) in the 0±80 cm depth for MP and SS treatments in 1992, 1993 and 1994. The bars indicate standard error (n 8).
the CDS treatment was consistently higher than in the drainage treatment in 1993 and 1994 (Fig. 2). Due to the wet growing season, there was only a small difference in soil profile water between the drainage and CDS treatments in 1992 (Fig. 2). On average, the soil profile water in the 0±80 cm depth was much higher in 1992 than in 1993 and 1994 (Figs. 1 and 2).
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Fig. 2. Total soil profile water content (mm) in the 0±80 cm depth for regular tile drainage (DR) and controlled drainage/subirrigation (CDS) treatments in 1992, 1993 and 1994. The bars indicate standard error (n 8).
3.3. Evapotranspiration There was no significant tillage water table interactions for the water balance components (Table 2). Tillage had no significant effect on cropping season evapotranspiration in all 3 years (Table 2 and Fig. 3A). The controlled drainage/
Table 2 Statistical significance of effects of tillage (T) and water table treatments (WT) on cumulative evapotranspiration (ET), surface runoff (SR), tile drainage (TD) and change in soil profile water content within the root-zone (DWC) during annual, cropping and non-cropping periodsa Year
Season
T ET
WT SR
TD
DWC
ET
SR
TD
DWC
ET
SR
TD
DWC
± ns ±
***
***
***
**
***
**
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
1992 Annual Cropping Non-cropping
± ns ±
ns ns ns
ns ns ns
ns
1993 Annual Cropping Non-cropping
± ns ±
ns ns
ns
±
*
ns
ns ns ns
1994 Annual Cropping Non-cropping
± ns ±
**
ns ns ns
ns ns ns
ns **
**
* *
T WT
**
*
**
***
**
**
**
±
**
*
ns
±
**
*
*
***
*
**
**
±
**
ns
ns
a
ns: not significant at the P < 0:05 level. Significant at P < 0:05 level. ** Significant at P < 0:01 level. *** Significant at P < 0:001 level. *
Fig. 3. Evapotranspiration for: (A) MP and SS treatments and (B) DR and CDS treatments in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
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subirrigation treatments (CDS) significantly increased (P < 0:001) cropping season evapotranspiration in 1993 and 1994 (Table 2 and Fig. 3B). The maize grown on the CDS treatments consumed an average of 87 mm more water than the drainage treatments during the dry years of 1993 and 1994. The CDS treatment had no significant effect on cropping season evapotranspiration during the wet year of 1992 (Table 2 and Fig. 3B). 3.4. Surface runoff The SS tillage increased total annual SR relative to the MP tillage in all 3 years, but this increase was significant (P < 0:01) only in 1994 (Table 2 and Fig. 4A). During the cropping period, SR was not affected by tillage treatments (Table 2 and Fig. 4B), but the SS tillage increased SR in all 3 years during the non-cropping period, although this increased was not significant in 1992 (Table 2 and Fig. 4C).
Fig. 4. Surface runoff for MP and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
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Fig. 5. Surface runoff for DR and CDS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
The CDS treatment had significantly higher SR than the DR treatments for all 3 years regardless of cropping periods (Table 2 and Fig. 5). Although about 66% of the total annual precipitation occurred in the 7 month cropping period (April±October), it produced only 31% of the total annual surface runoff. The remaining 69% of the SR occurred in the 5 month non-cropping period (November±March). 3.5. Tile drainage Tillage had very little effect on TD (Table 2 and Fig. 6) except during the 1993 cropping period where the SS tillage significantly increased (P < 0:01) TD relative to the MP tillage (Table 2 and Fig. 6B). The CDS treatment produced consistently lower TD than the DR treatment in all 3 years, except for the 1994 non-cropping period (Table 2 and Fig. 7). Averaged over the 3-year study period, 64% of TD occurred during the noncropping period.
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Fig. 6. Tile drainage for MP and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
3.6. Net change in soil profile water content Tillage had no effect on annual net change in soil profile water content in the 0±80 cm root-zone in all 3 years (Table 2 and Fig. 8A). In 1992, however, the SS tillage had greater soil profile water content change during the cropping period (Fig. 8B), but less soil profile water content change during the non-cropping period (Fig. 8C) relative to MP. There were no significant differences between tillage treatments in soil water content change during 1993 and 1994 regardless cropping periods (Table 2 and Fig. 8). The negative cumulative soil profile water content change (net decrease in soil profile water content) for both tillage treatments was observed during the cropping period in 1993 and 1994 (Fig. 8B), which was a result of below normal growing season precipitation and low soil profile water content in the 0±80 cm depth (Fig. 1). The CDS treatments significantly increased net change in soil profile water content relative to the DR treatments both annually and during the cropping periods in 1993 and 1994 (Table 2 and Fig. 9A and B), due to the addition of subirrigation water during the growing season. There were no significant
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Fig. 7. Tile drainage for CDS and DR treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
differences between the two water table treatments with respect to soil profile water content change for 1992 (Fig. 9A±C) and for the non-cropping period in all 3 years (Fig. 9C). 4. Discussion Controlled drainage and subirrigation had significant impacts on the overall water balance. Relative to DR treatment, the CDS treatments increased crop evapotranspiration and reduced the soil water deficit during the cropping period, which has been reported to increase crop production (Cooper et al., 1991; Madramootoo et al., 1993; Tan et al., 1993, 1999). The CDS treatments reduced TD volume and increased soil water content in the root zone relative to DR treatments. Reduction in TD volume for controlled drainage and subirrigation systems has been reported by many researchers (Gilliam et al., 1979; Tan et al., 1993, 1998, 1999). The DR treatments produced significantly greater TD than the
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Fig. 8. Net change in soil profile water content in the 0±80 cm depth for moldboard plow (MP) and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
CDS treatments which can in turn cause greater nitrate leaching, as has been documented elsewhere (Gilliam et al., 1979; Drury et al., 1996; Tan et al., 1993, 1998, 1999). Controlled drainage and subirrigation is thus a possible means for reducing the entry of agricultural chemicals into groundwater (Gilliam et al., 1979; Fogiel and Belcher, 1991; Drury et al., 1996; Tan et al., 1993, 1998, 1999). The CDS treatments had higher SR than the DR treatments, most likely because of the generally wetter soil profile. The dynamics of the partitioning between SR and TD discharge through tiles was complex. Surface runoff occurred during periods of heavy precipitation or snowmelt; and varied greatly between these events, depending on rainfall intensities, the amount of frost in the soil and the existing near-surface soil moisture prior to the event (Johnsson and Ludin, 1991). It may be possible to reduce the amount of SR from CDS treatments by careful adjustment of near-surface soil moisture and/or by installing the tile at a deeper depth. Deeper tile may also increase the water storage capacity of the soil profile.
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Fig. 9. Net change in soil profile water content in the 0±80 cm depth for DR and controlled drainage/ subirrigation (CDS) treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
In this study, tillage had little effect on water balance, a small and inconsistent effect on TD, SR and soil profile water content and no significant effect on crop evapotranspiration. The SS increased SR during non-cropping periods in 1993 and 1994, most likely because of greater bulk density at 0±10 cm soil depth relative to MP (Vyn and Raimbault, 1993). Van Vliet et al. (1993) reported that conventional tillage had significantly higher rainfall runoff and soil loss from snowmelt than zone tillage and ridge tillage. Their study was conducted on plots with 7.3±8% surface slope in contrast to our study located on plots with 0.05±0.10% surface slope. In our study, the SS tillage had been in place for only 3 years. In other long-term (>7 years) no-tillage studies, increased TD volume was reported by Tan et al. (1998) and various other researchers (Masse et al., 1996; Edwards et al., 1993). Long-term no-tillage resulted in greater preferential flow as a result of increased earthworm populations (Tan et al., 1998; Edwards et al., 1993). Much greater volumes of SR and TD occurred during the non-cropping period than during the cropping period. Over 65% of SR and TD occurred in the 5 month
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non-cropping period, even though precipitation during this period accounted for only 34% of the annual total. In order to reduce SR and TD, the cover crops, such as legumes or grasses could be grown during the non-cropping period. Bryant et al. (1987) reported lower TD and nitrate concentrations when forages were grown. 5. Conclusions A water balance approach has made it possible to identify the importance of different soil and water management systems on the partitioning of water amongst evapotranspiration, SR, TD and soil profile water content. Controlled drainage and subirrigation has been shown to strongly increase crop evapotranspiration and soil profile water content. It also decreased TD volume. Tillage, on the other hand, had little effect. Although use of controlled drainage and subirrigation with shallow tiles may increase SR, runoff accounts for only 8% of total annual water inputs (precipitation and/or subirrigation), whereas about 30% of the annual water input was removed from the field by TD. Crop evapotranspiration made use of 55% of the total annual water input, while change in soil profile water content accounted for about only 7% of the total annual input. Furthermore, over 65% of water loss by SR and TD occurred in the November±March non-cropping period for all treatments. Therefore, use of cover crops during the non-cropping period and/or increased soil organic matter to improve soil water storage capacity should reduce water loss and improve water quality. Acknowledgements This research was supported by grants from the Great Lakes Water Quality Preservation Fund. The expert technical assistance to M. Soultani, V. Bernyk, T. Oloya, D. MacTavish, G. Stasko, K Rinas, J. St. Denis and J. Stowe is gratefully acknowledged. References Baker, J.L., 1987. Hydrologic effects of conservation tillage and their importance relative to water quality. In: Logan, J.L., Davidson, J.M., Baker, J.L., Overcash, M.R. (Eds.), Effects of Conservation Tillage on Groundwater Quality: Nitrate and Pesticides. Lewis Publishers Inc., Chelsea, MI, pp. 113±124. Bryant, G.J., Irwin, R.W., Stone, J.A., 1987. Tile drain drainage under different crops. Can. Agric. Eng. 29, 117± 122. Cooper, R.L., Fausey, N.R., Streetes, J.G., 1991. Yield potential of soybean grown under a subirrigation/drainage water management system. Agron. J. 83 (6), 884±887. Drury, C.F., Tan, C.S., 1995. Long-term (35 years) effects of fertilization, rotation and weather on corn yields. Can. J. Plant Sci. 75, 355±362. Drury, C.F., Tan, C.S., Gaynor, J.D., Oloya, T.O., Welacky, T.W., 1996. Influence of controlled drainagesubirrigation on surface and tile drainage nitrate loss. J. Environ. Qual. 25, 317±324. Drury, C.F., Tan, C.S., Welacky, T.W., Oloya, T.O., Hamill, A.S., Weaver, S.E., 1999. Red clover and tillage influence on soil temperature, water content and corn emergence. Agron. J. 91, 101±108. Edwards, W.M., Shipitalo, M.J., Owens, L.B., Dick, W.A., 1993. Factors affecting preferential flow of water and atrazine through earthworm burrows under continuous no-till corn. J. Environ. Qual. 22, 453±457.
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Fogiel, A.C., Belcher, H.W., 1991. Water quality impacts of water table management system ASAE paper 912596. ASAE, ST. Joseph, MI. Gilliam, J.W., Skaggs, R.W., Weed, S.W., 1979. Drainage control diminish nitrate loss from agriculture fields. J. Environ. Qual. 8, 137±142. Johnsson, H., Ludin, L.C., 1991. Surface runoff and soil water percolation as affected by snow and soil frost. J. Hydrol. 122, 141±159. Lee, L.K., Nielsen, E.G., 1987. The extent and costs of groundwater contamination by agriculture. J. Soil Wat. Conserv. 42 (4), 243±248. Madramootoo, C.A., Dodds, G.T., Popadopoulos, A., 1993. Agronomic and environmental benefits of water table management. J. Irri. Drain. Eng. 119 (6), 1052±1065. Masse, L., Patni, N.K., Jui, P.Y., Clegg, B.S., 1996. Tile effluent quality and chemical losses under conventional and no tillage. Part 2. Atrazine and metolachlor. Transactions ASAE 39 (5), 1673±1679. Soultani, M., Tan, C.S., Gaynor, J.D., Neveu, R., Drury, C.F., 1993. Measuring and sampling surface runoff and subsurface drain outflow volume. Appl. Eng. Agric. 9, 447±450. Stone, J.A., Mckeague, J.A., Protz, R., 1987. Corn root distribution in relation to long-term rotations on a poorly drained clay loam soil. Can. J. Plant Sci. 67, 231±234. Tan, C.S., Drury, C.F., Gaynor, J.D., Welacky, T.W., 1993. Integrated soil, crop and water management system to abate herbicide and nitrate contamination of the Great Lakes. Wat. Sci. Tech. 28, 497±507. Tan, C.S., Drury, C.F., Soultani, M., van Wesenbeeck, I.J., Ng, H.Y.F., Gaynor, J.D., Welacky, T.W., 1998. Effect of controlled drainage and tillage on soil structure and tile drainage nitrate loss at the field scale. Wat. Sci. Tech. 38, 103±110. Tan, C.S., Drury, C.F., Ng, H.Y.F., Gaynor, J.D., 1999. Effect of controlled drainage and subirrigation on subsurface tile drainage nitrate loss and crop yield at the farm scale. Canadian Wat. Res. J. 24 (3), 177±186. Treidl, R.A. (Ed.), 1979. Handbook on Agricultural on Forest Meteorology. Part II. Fisheries and Environment Canada. Van Vliet, L.J.P., Kline, R., Hall, J.W., 1993. Effect of three tillage treatments on seasonal runoff and soil loss in the Peace River region. Can. J. Soil Sci. 73, 469±480. Vyn, T.J., Raimbault, B.A., 1993. Long-term effect of five tillage systems on corn response and soil structure. Agron. J. 85, 1074±1079.
Effect of tillage and water table control on evapotranspiration, surface runoff, tile drainage and soil water content under maize on a clay loam soil C.S. Tan*, C.F. Drury, J.D. Gaynor, T.W. Welacky, W.D. Reynolds Agriculture and Agri-Food Canada, Greenhouse and Processing Crops Research Center, 2585 Highway 20, E., Harrow, Ont., Canada N0R 1G0 Accepted 26 September 2001
Abstract Two tillage and two water table control treatments under continuous maize cropping were evaluated over a 3-year period (1992±1994) for their effects on evapotranspiration, surface runoff (SR), tile drainage (TD) and soil water content in the root-zone on a clay loam soil in southern Ontario. The tillage treatments included soil saver (SS, reduced tillage) and moldboard plow (MP, conventional tillage). The water table control treatments included controlled drainage-subirrigation (CDS) and regular tile drainage (DR). There was no signi®cant difference (P < 0:05) in evapotranspiration estimates between the SS and MP tillage treatments. The SS tillage increased SR compared with MP tillage during the non-cropping periods in 1993 and 1994, but not in 1992. Relative to MP, the SS tillage increased soil pro®le water content during the cropping period but decreased soil pro®le water content during the non-cropping period in 1992. The CDS treatment produced signi®cantly higher (P < 0:05) evapotranspiration and soil water content than the drainage treatment during the dry 1993 and 1994 years, but not during the wet 1992 year. The CDS treatment also had signi®cantly lower (P < 0:05) TD and higher SR than the drainage treatment. For all the treatments, over 65% of SR and TD occurred in the 5 month non-cropping period from November to March. Of the total annual water input (precipitation and/or subirrigation) to the ®eld site, 8% was partitioned to SR, 30% was partitioned to TD, 55% was removed by crop and soil evapotranspiration and 7% was accounted for by changes in soil pro®le water content. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Tillage; Controlled drainage/subirrigation; Evapotranspiration; Runoff; Tile drainage; Soil pro®le water content * Corresponding author. Tel.: 1-519-738-2251x475; fax: 1-519-738-2929. E-mail address: [email protected] (C.S. Tan).
0378-3774/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 1 ) 0 0 1 7 8 - 0
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1. Introduction One of main challenges to agriculture on fine-textured soils is managing the amount and temporal distribution of soil water in the crop root-zone. Too much water may result in insufficient root-zone aeration and it may also impede or prevent critical tillage, planting and harvesting operations (Drury et al., 1999). Too little soil water, on the other hand, may cause crop drought stress and subsequent yield reduction (Drury and Tan, 1995; Tan et al., 1993). Tillage type, cropping practices and water table management can have substantial effects on the amount and temporal distribution of root-zone soil water through their impacts on SR, TD and crop evapotranspiration (Bryant et al., 1987; Van Vliet et al., 1993). It is well established, for example, that no-tillage in wet temperate climates can reduce SR (Lee and Nielsen, 1987), but this can also increase infiltration and subsequent tile drainage (Tan et al., 1998). The mechanism by which this occurs is not well understood, however, and it is likely to vary with physiography, soil type, climate and the duration of no-tillage (Baker, 1987). The type of crop and/or crop rotation can also affect root-zone soil water by influencing the partitioning of water amongst runoff, evapotranspiration and infiltration (Bryant et al., 1987). The shallow and closely spaced tile drainage systems usually found in the fine-textured soils of southwestern Ontario are designed to permanently remove excess water as quickly as possible during the spring and fall so that root-zone aeration and agronomic operations are not impeded. Although these systems perform this function rather well, in doing so they may also reduce soil water storage and thereby indirectly contribute to root-zone soil water deficits during the growing season when precipitation is low and evapotranspiration is high. In this regard, attachment of water table control structures to existing tile drainage systems has met with some success at reducing root-zone soil water deficits in fine-textured soils, but this appears to be only a partial solution (Tan et al., 1993). What is needed for fine-textured soils in wet temperate regions, such as southwestern Ontario are water/soil/crop management strategies that can quickly remove excess soil water, but also maximize and/or replenish soil water for crop use during times of growing season water deficit. As an initial step toward this overall goal, the objective of this study was to use a water balance approach to elucidate the impacts of two tillage systems (MP, SS) and controlled drainage with subsurface irrigation on evapotranspiration, SR, and change in soil profile water content under maize (Zea mays L.) grown on a clay loam soil in southwestern Ontario. 2. Materials and methods 2.1. Site description The study included two tillage and two water management treatments, replicated four times, on sixteen 15 m wide by 67 m long field plots (Tan et al., 1993; Drury et al., 1996). The two tillage treatments were moldboard plow (MP, conventional tillage) and soil saver (SS, reduced tillage). The two water management treatments were regular
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drainage (DR) only and controlled tile drainage with subsurface irrigation (controlled drainage-subirrigation, CDS). The site is located on poorly drained Brookston clay loam soil (Typic Argiaquoll) which is the dominant soil type in Essex County, Ontario, comprising over 80% of the agricultural land. The Ap horizon is a dark brown, clay loam 30 cm deep with 1.5% organic carbon. The B horizon has a clay texture to a depth of 1.5 m. Each of the 16 field plots was hydraulically isolated and had two 104 mm diameter tile lines at 7.5 m spacing and an average depth of 0.6 m. The water table was maintained at 30 cm below ground level in the CDS treatments through the use of tile outflow risers and subirrigation during the growing season (Tan et al., 1993). The risers were removed briefly in the spring and fall to allow planting and harvesting, then reinstalled after harvest to maintain the water table at 30 cm depth for the winter and spring periods. No drainage control or subirrigation occurred in the DR treatments. 2.2. Agronomy The MP plots were plowed to a depth of 15 cm in the fall and disced in the spring for seedbed preparation. The SS plots were prepared in the fall with a Glencoe soil saver implement (Model F551-A, series 3, Glencoe, Farmhand Div, Excelsior, MN) equipped with seven 35 cm sweeps at 38 cm spacing which disturbed the soil to a depth of 15 cm. No spring seed bed preparation was performed in the SS plots before planting. A four row Kinze (Kinze Manufacturing Co., Williamsburg, IA) planter seeded maize (Zea mays L., Pioneer 3573) at 65,000 seeds ha±1 in 75 cm wide rows. Fertilizer (8-32-16) was band applied beside the seed at a rate of 132 kg ha 1. A brush applicator applied urea (46-0-0) at the six-leaf stage at a rate based on the average nitrate soil test and previous crop history (Drury et al., 1996). Atrazine (6-chloro-N-ethyl-N0 -(1-methylethyl)-1,3,5-triazine2,4-diamine), metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin5(4H)-one) and metolachlor (2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-methoxy-1methylethyl) acetamide) were banded over the maize row immediately after planting to control weeds. 2.3. Surface runoff and TD measurements Surface runoff (SR) and TD water from the 16 experimental plots was routed to a central instrumentation building and collected in 32 polyethylene sumps (500 mm diameter by 750 mm deep). Each sump was equipped with an electrical, float activated, effluent pump. SR and TD from each individual plot flowing into the respective sumps were pumped through water metres to an outlet drain. A multi-channel datalogger utilized the analog signal of the water meters to monitor, measure and store water volume data on a continuous basis (Soultani et al., 1993). 2.4. Soil profile water content Soil profile water content was monitored using a subsurface neutron moisture probe (model CPN 503). Three aluminum access tubes were inserted to a depth of 120 cm in
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each plot. The measurements were taken three times per week at 20 cm intervals from 0 to 100 cm depth during the growing season. The neutron probe was calibrated against gravimetric sampling using, yv 0:163R/Rw 0:026 (r 2 0:984 and Syx 0:012), where yv is the volumetric soil water content (m3 m 3), R the neutron meter count rate in the soil and Rw the standard meter count rate in the shield. As there is little evidence of maize root growth below 80 cm in this poorly drained clayey soil (Stone et al., 1987), the volumetric soil water content obtained by the neutron probe was converted to soil moisture (SM) in the top 800 mm of soil depth using, SM yv 800 (mm). 2.5. Meteorological measurement Weather data were recorded within 0.5 km of the experimental site. These measurements included air temperature, solar radiation, rainfall, wind speed and direction and relative humidity. 2.6. Estimating evapotranspiration and change in soil profile water content The water balance can be used as a means for measuring evapotranspiration (ET) during the cropping period (April±October) using: ETt
t X
Pd Id
SRd
TDd
DWCd
(1)
d1
where, DWCd SMd
SMd
(2)
1
and ET is evapotranspiration (mm), P the precipitation (mm), I the subirrigation amount (mm), SR the surface runoff (mm), TD the tile drainage (mm), DWC the change in soil pro®le water content in the 0±80 cm depth (mm), t the number of days over which the evapotranspiration and change in soil pro®le water content are calculated, d the day (d 1; 2; 3; . . . ; t) and SMd and SMd 1 are the soil water content in the 0±80 cm depth (mm) on days d and d 1, respectively. The P, SR and TD are measured continuously all year. Subirrigation water was applied only during summer (June±September) on an as needed basis and was accurately measured using a water meter. The change in soil pro®le water content P in the 0±80 cm depth during summer (DWCt) was calculated using, DWCt td1 SMd SMd 1 with SMd and SMd 1 measured using the neutron moisture probe. A positive DWC value indicates a net increase in soil pro®le water content, while a negative DWC value indicates a net decrease. As shown in Table 20 of Treidl (1979), potential ET is effectively zero in our climate region during the noncropping period (November±March). Hence, the change in soil pro®le water content during the winter (DWCt) can be calculated using: DWCt
t X Pd
SRd
TDd
(3)
d1
Deep drainage and/or recharge from below the 80 cm depth could introduce error into
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Eqs. (1)±(3). Inspection of the pro®le soil water content between 80 and 100 cm depth indicated, however that only very small hydraulic gradients existed in this depth range. In addition, the saturated hydraulic conductivity below 80 cm was very low at <4.6 cm per day. Consequently, deep drainage and recharge from below 80 cm depth were negligible in this study. 3. Results 3.1. Precipitation and subirrigation amount The monthly precipitation for the three experimental years and the corresponding 48 year averages are shown in Table 1. During 1992, total annual precipitation was 98.6 mm above the 48 year mean and cropping season precipitation (April±November), was 87 mm above the 48 year mean. Both 1993 and 1994 years were dry with total precipitation of 180.9 and 165.6 mm below the 48 year mean, respectively (Table 1). For all 3 years, subsurface irrigation for the CDS treatments was initiated during the first week of June and terminated at the end of August. As the 1992 cropping season was wet, only 5.7 mm of water was applied to the CDS treatments during that year. On the other hand, the CDS treatments received 126 and 115 mm of subsurface irrigation water in 1993 and 1994, respectively, owing to low growing season rainfall in those years. 3.2. Soil profile water The soil profile water in the 0±80 cm depth during the growing season was similar between the MP and SS tillages for all 3 years (Fig. 1). However, the soil profile water in Table 1 Monthly field site precipitation (mm) in 1992, 1993, 1994 and 48 year average Month
January February March April May June July August September October November December Total
Precipitation (mm) 1992
1993
1994
48 year average
33.5 44.0 65.0 91.5 52.5 67.0 118.0 129.0 133.5 50.0 129.5 54.0 967.5
94.0 8.0 41.0 81.0 50.0 108.5 47.5 29.0 107.0 52.0 49.5 20.5 688.0
73.8 40.8 52.5 74.5 47.3 83.3 31.0 111.3 32.3 61.5 56.5 38.5 703.3
51.7 44.8 67.7 80.0 73.3 95.8 85.5 82.5 83.1 54.3 73.1 77.1 868.9
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Fig. 1. Total soil profile water content (mm) in the 0±80 cm depth for MP and SS treatments in 1992, 1993 and 1994. The bars indicate standard error (n 8).
the CDS treatment was consistently higher than in the drainage treatment in 1993 and 1994 (Fig. 2). Due to the wet growing season, there was only a small difference in soil profile water between the drainage and CDS treatments in 1992 (Fig. 2). On average, the soil profile water in the 0±80 cm depth was much higher in 1992 than in 1993 and 1994 (Figs. 1 and 2).
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Fig. 2. Total soil profile water content (mm) in the 0±80 cm depth for regular tile drainage (DR) and controlled drainage/subirrigation (CDS) treatments in 1992, 1993 and 1994. The bars indicate standard error (n 8).
3.3. Evapotranspiration There was no significant tillage water table interactions for the water balance components (Table 2). Tillage had no significant effect on cropping season evapotranspiration in all 3 years (Table 2 and Fig. 3A). The controlled drainage/
Table 2 Statistical significance of effects of tillage (T) and water table treatments (WT) on cumulative evapotranspiration (ET), surface runoff (SR), tile drainage (TD) and change in soil profile water content within the root-zone (DWC) during annual, cropping and non-cropping periodsa Year
Season
T ET
WT SR
TD
DWC
ET
SR
TD
DWC
ET
SR
TD
DWC
± ns ±
***
***
***
**
***
**
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
± ns ±
ns ns ns
ns ns ns
ns ns ns
1992 Annual Cropping Non-cropping
± ns ±
ns ns ns
ns ns ns
ns
1993 Annual Cropping Non-cropping
± ns ±
ns ns
ns
±
*
ns
ns ns ns
1994 Annual Cropping Non-cropping
± ns ±
**
ns ns ns
ns ns ns
ns **
**
* *
T WT
**
*
**
***
**
**
**
±
**
*
ns
±
**
*
*
***
*
**
**
±
**
ns
ns
a
ns: not significant at the P < 0:05 level. Significant at P < 0:05 level. ** Significant at P < 0:01 level. *** Significant at P < 0:001 level. *
Fig. 3. Evapotranspiration for: (A) MP and SS treatments and (B) DR and CDS treatments in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
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subirrigation treatments (CDS) significantly increased (P < 0:001) cropping season evapotranspiration in 1993 and 1994 (Table 2 and Fig. 3B). The maize grown on the CDS treatments consumed an average of 87 mm more water than the drainage treatments during the dry years of 1993 and 1994. The CDS treatment had no significant effect on cropping season evapotranspiration during the wet year of 1992 (Table 2 and Fig. 3B). 3.4. Surface runoff The SS tillage increased total annual SR relative to the MP tillage in all 3 years, but this increase was significant (P < 0:01) only in 1994 (Table 2 and Fig. 4A). During the cropping period, SR was not affected by tillage treatments (Table 2 and Fig. 4B), but the SS tillage increased SR in all 3 years during the non-cropping period, although this increased was not significant in 1992 (Table 2 and Fig. 4C).
Fig. 4. Surface runoff for MP and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
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Fig. 5. Surface runoff for DR and CDS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
The CDS treatment had significantly higher SR than the DR treatments for all 3 years regardless of cropping periods (Table 2 and Fig. 5). Although about 66% of the total annual precipitation occurred in the 7 month cropping period (April±October), it produced only 31% of the total annual surface runoff. The remaining 69% of the SR occurred in the 5 month non-cropping period (November±March). 3.5. Tile drainage Tillage had very little effect on TD (Table 2 and Fig. 6) except during the 1993 cropping period where the SS tillage significantly increased (P < 0:01) TD relative to the MP tillage (Table 2 and Fig. 6B). The CDS treatment produced consistently lower TD than the DR treatment in all 3 years, except for the 1994 non-cropping period (Table 2 and Fig. 7). Averaged over the 3-year study period, 64% of TD occurred during the noncropping period.
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Fig. 6. Tile drainage for MP and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
3.6. Net change in soil profile water content Tillage had no effect on annual net change in soil profile water content in the 0±80 cm root-zone in all 3 years (Table 2 and Fig. 8A). In 1992, however, the SS tillage had greater soil profile water content change during the cropping period (Fig. 8B), but less soil profile water content change during the non-cropping period (Fig. 8C) relative to MP. There were no significant differences between tillage treatments in soil water content change during 1993 and 1994 regardless cropping periods (Table 2 and Fig. 8). The negative cumulative soil profile water content change (net decrease in soil profile water content) for both tillage treatments was observed during the cropping period in 1993 and 1994 (Fig. 8B), which was a result of below normal growing season precipitation and low soil profile water content in the 0±80 cm depth (Fig. 1). The CDS treatments significantly increased net change in soil profile water content relative to the DR treatments both annually and during the cropping periods in 1993 and 1994 (Table 2 and Fig. 9A and B), due to the addition of subirrigation water during the growing season. There were no significant
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Fig. 7. Tile drainage for CDS and DR treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
differences between the two water table treatments with respect to soil profile water content change for 1992 (Fig. 9A±C) and for the non-cropping period in all 3 years (Fig. 9C). 4. Discussion Controlled drainage and subirrigation had significant impacts on the overall water balance. Relative to DR treatment, the CDS treatments increased crop evapotranspiration and reduced the soil water deficit during the cropping period, which has been reported to increase crop production (Cooper et al., 1991; Madramootoo et al., 1993; Tan et al., 1993, 1999). The CDS treatments reduced TD volume and increased soil water content in the root zone relative to DR treatments. Reduction in TD volume for controlled drainage and subirrigation systems has been reported by many researchers (Gilliam et al., 1979; Tan et al., 1993, 1998, 1999). The DR treatments produced significantly greater TD than the
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Fig. 8. Net change in soil profile water content in the 0±80 cm depth for moldboard plow (MP) and SS treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
CDS treatments which can in turn cause greater nitrate leaching, as has been documented elsewhere (Gilliam et al., 1979; Drury et al., 1996; Tan et al., 1993, 1998, 1999). Controlled drainage and subirrigation is thus a possible means for reducing the entry of agricultural chemicals into groundwater (Gilliam et al., 1979; Fogiel and Belcher, 1991; Drury et al., 1996; Tan et al., 1993, 1998, 1999). The CDS treatments had higher SR than the DR treatments, most likely because of the generally wetter soil profile. The dynamics of the partitioning between SR and TD discharge through tiles was complex. Surface runoff occurred during periods of heavy precipitation or snowmelt; and varied greatly between these events, depending on rainfall intensities, the amount of frost in the soil and the existing near-surface soil moisture prior to the event (Johnsson and Ludin, 1991). It may be possible to reduce the amount of SR from CDS treatments by careful adjustment of near-surface soil moisture and/or by installing the tile at a deeper depth. Deeper tile may also increase the water storage capacity of the soil profile.
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Fig. 9. Net change in soil profile water content in the 0±80 cm depth for DR and controlled drainage/ subirrigation (CDS) treatments during (A) annual, (B) cropping and (C) non-cropping periods in 1992, 1993 and 1994. Bars within years labeled with the same letter are not significantly different at P < 0:05.
In this study, tillage had little effect on water balance, a small and inconsistent effect on TD, SR and soil profile water content and no significant effect on crop evapotranspiration. The SS increased SR during non-cropping periods in 1993 and 1994, most likely because of greater bulk density at 0±10 cm soil depth relative to MP (Vyn and Raimbault, 1993). Van Vliet et al. (1993) reported that conventional tillage had significantly higher rainfall runoff and soil loss from snowmelt than zone tillage and ridge tillage. Their study was conducted on plots with 7.3±8% surface slope in contrast to our study located on plots with 0.05±0.10% surface slope. In our study, the SS tillage had been in place for only 3 years. In other long-term (>7 years) no-tillage studies, increased TD volume was reported by Tan et al. (1998) and various other researchers (Masse et al., 1996; Edwards et al., 1993). Long-term no-tillage resulted in greater preferential flow as a result of increased earthworm populations (Tan et al., 1998; Edwards et al., 1993). Much greater volumes of SR and TD occurred during the non-cropping period than during the cropping period. Over 65% of SR and TD occurred in the 5 month
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non-cropping period, even though precipitation during this period accounted for only 34% of the annual total. In order to reduce SR and TD, the cover crops, such as legumes or grasses could be grown during the non-cropping period. Bryant et al. (1987) reported lower TD and nitrate concentrations when forages were grown. 5. Conclusions A water balance approach has made it possible to identify the importance of different soil and water management systems on the partitioning of water amongst evapotranspiration, SR, TD and soil profile water content. Controlled drainage and subirrigation has been shown to strongly increase crop evapotranspiration and soil profile water content. It also decreased TD volume. Tillage, on the other hand, had little effect. Although use of controlled drainage and subirrigation with shallow tiles may increase SR, runoff accounts for only 8% of total annual water inputs (precipitation and/or subirrigation), whereas about 30% of the annual water input was removed from the field by TD. Crop evapotranspiration made use of 55% of the total annual water input, while change in soil profile water content accounted for about only 7% of the total annual input. Furthermore, over 65% of water loss by SR and TD occurred in the November±March non-cropping period for all treatments. Therefore, use of cover crops during the non-cropping period and/or increased soil organic matter to improve soil water storage capacity should reduce water loss and improve water quality. Acknowledgements This research was supported by grants from the Great Lakes Water Quality Preservation Fund. The expert technical assistance to M. Soultani, V. Bernyk, T. Oloya, D. MacTavish, G. Stasko, K Rinas, J. St. Denis and J. Stowe is gratefully acknowledged. References Baker, J.L., 1987. Hydrologic effects of conservation tillage and their importance relative to water quality. In: Logan, J.L., Davidson, J.M., Baker, J.L., Overcash, M.R. (Eds.), Effects of Conservation Tillage on Groundwater Quality: Nitrate and Pesticides. Lewis Publishers Inc., Chelsea, MI, pp. 113±124. Bryant, G.J., Irwin, R.W., Stone, J.A., 1987. Tile drain drainage under different crops. Can. Agric. Eng. 29, 117± 122. Cooper, R.L., Fausey, N.R., Streetes, J.G., 1991. Yield potential of soybean grown under a subirrigation/drainage water management system. Agron. J. 83 (6), 884±887. Drury, C.F., Tan, C.S., 1995. Long-term (35 years) effects of fertilization, rotation and weather on corn yields. Can. J. Plant Sci. 75, 355±362. Drury, C.F., Tan, C.S., Gaynor, J.D., Oloya, T.O., Welacky, T.W., 1996. Influence of controlled drainagesubirrigation on surface and tile drainage nitrate loss. J. Environ. Qual. 25, 317±324. Drury, C.F., Tan, C.S., Welacky, T.W., Oloya, T.O., Hamill, A.S., Weaver, S.E., 1999. Red clover and tillage influence on soil temperature, water content and corn emergence. Agron. J. 91, 101±108. Edwards, W.M., Shipitalo, M.J., Owens, L.B., Dick, W.A., 1993. Factors affecting preferential flow of water and atrazine through earthworm burrows under continuous no-till corn. J. Environ. Qual. 22, 453±457.
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