HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Bargar, B. Articles by Jaynes, D. Search for Related Content PubMed Articles by Bargar, B. Articles by Jaynes, D. Agricola Articles by Bargar, B. Articles by Jaynes, D.

DIVISION S-6-SOIL & WATER MANAGEMENT & CONSERVATION

Soil Water Recharge under Uncropped Ridges and Furrows

^a The Scotts Co., 14310 Scottslawn Rd., Marysville, OH 43041, previously Dep. of Agronomy, Iowa State Univ., Ames, IA 50011 USA
^b Dep. of Agronomy, Iowa State Univ., Ames, IA 50011 USA
^c USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011-3120 USA

jbswan{at}bellsouth.net

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Nitrate leaching to ground and surface water is an increasing concern in agriculture. Ridge tillage and associated residue management offer potential for modifying the pattern of soil water and solute movement to reduce NO₃ leaching from corn (Zea mays L.) production. To test this idea we used time domain reflectometry (TDR) measurements of volumetric soil water content () at 0.5-h intervals following natural rainfall events to determine the pattern of infiltration and soil water recharge for uncropped row and furrow positions in long-term ridge-tillage fields. Soil water content was measured under adjacent rows and three adjoining furrows for 103 d in 1992 on a Clarion loam (fine-loamy, mixed mesic, Typic Hapludoll) near Boone, IA and 96 d on Monona silt loam (fine-silty, mixed mesic, Typic Hapludoll) near Treynor, IA. During rainfall, infiltration occurred primarily in furrows, as indicated by greater and more rapid initial increases in for furrow than for row positions at the same elevation. Following redistribution and evaporation, row and furrow positions at the same elevation had values differing by <0.03 m³ m^-3. Changes in profile average of rows and furrows between rainfall events were closely correlated (R² > 0.94). Storage between rainfall events decreased with increasing initial and time interval between events (R² > 0.68), consequently soil water recharge occurred as a series of stepwise increases of . These results support the conclusion that water infiltrated in furrows and primarily moved laterally to row positions, minimizing downward water movement under the row. These results explain greater solute movement under furrows than under rows, as found in several short-term studies.

Abbreviations: C, center furrow • DOY, Day of the Year • E, east furrow • F, furrow • R, row • SH, shoulder • TDR, time domain reflectometry • W, west furrow • , volumetric soil water content

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
REDUCTION IN OFF-FARM MOVEMENT of agricultural chemicals, in particular leaching of NO₃, requires improved understanding of the effect of soil management practices on soil water and solute movement under a range of soil and weather conditions. Ridge tillage and associated residue management offer potential for modifying the pattern of soil water and solute movement. Ridges affect soil temperature and water content (Shaw and Buchele, 1957; Burrows, 1963; Radke, 1982; Benjamin et al., 1990a, 1990b; Horton et al., 1989), as well as soil water and solute movement (Kemper et al., 1975; Hamlett et al., 1990; Clay et al., 1992, 1994). Kemper et al. (1975) used furrow irrigation in the absence of plants, while the latter three studies measured leaching using rainfall simulation rather than natural rainfall. When plants do not affect distribution during rainfall, more water accumulates in the furrow than in the ridge (Hamlett et al., 1990). Consequently, water contents in the upper soil layers of a furrow are higher during and directly after rainfall than in the row at an equivalent elevation, indicating greater water movement in furrows than under ridges. Timing and amount of rainfall events, along with initial soil water content, may affect the pattern of soil water recharge. Hamlett et al. (1990) found greater water storage under ridges than under tracked furrows 2 d after a 50-mm artificial rainfall, but 4 d after a 72-mm artificial rainfall the results were reversed. Bresler et al. (1969) found that the effect of hysteresis was to decrease the depth of wetting and increase the water content of the wetted zone. They also found that rate, amount, and distribution of wetting affected evaporation. Greater evaporation was associated with higher water content and smaller wetting depth. Under field conditions, soil water recharge for ridge tillage is complicated by the variability in amount, intensity, duration, and frequency of natural rainfall events, and by the effect of surface configuration and residue on infiltration and evaporation. The presence of vegetation causes additional complexity by affecting infiltration and evaporation, and soil water extraction by roots directly affects soil water content. We conducted the study without growing plants to avoid the added complication on soil water movement and storage caused by vegetation. Our objective was to determine the pattern of soil water recharge with time following individual natural rainfall events in an uncropped ridge tillage system. We proposed the testable null hypothesis that surface configuration does not affect soil water content and movement. As part of the research, we also compared the changes in determined by half-hourly TDR measurements, daily averages of these TDR measurements, and weekly neutron thermalization measurements of to assess the effect of sampling frequency and sample volume.

	Materials and methods

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Measurement sites were at the USDA Deep Loess Research Station, Treynor, IA on loess-derived Monona silt loam, and a farm near Boone, IA on Clarion loam derived from glacial till parent material. Both sites were nearly level with slopes of 1% or less and had been in ridge tillage for >10 yr. Both soils are well drained and represent distinct agriculturally important soil regions in Iowa. Soil texture of the two soils differs, reflecting different parent materials (Tables 1 and 2) . Sand content and bulk density increased with depth at the Clarion silt loam site. Both soils have high water-holding capacities as indicated by water retention measurements. The depth to the water table at the Treynor site was >10 m, but ranged between 1.2 and 2.5 m during the study period at the Boone site. Previous crops were corn at Treynor and soybean [Glycine max (L.) Merr.] at Boone. Row direction was north–south. The study sites were a 16 by 16 m area at Treynor and 9.1 m wide by 16 m long area at Boone. Crop residue cover was confined to furrows by the ridge-tillage planting operation and plants were removed by hand from the study area. Percentage of surface residue cover was determined from photographs using the method of Laflen et al. (1981). Residue cover remained relatively constant at the Boone site, but during the study, sediment movement from ridges covered part of the residue at Treynor. The Boone site was monitored from 16 May to 29 Aug. 1992 and the Treynor site from 4 June to 8 Sept. 1992. Row spacing was 76 cm and ridge height was 8 cm at Boone. At Treynor, row spacing was 97 cm and ridge height was 11 cm. At both sites, the center furrow (C) received no wheel traffic, while adjoining east (E) and west (W) furrows received wheel traffic. At Treynor bulk density measurements (n = 7) at three separate times for the 5-cm furrow depth were consistently greater for tracked furrows (1.44 ± 0.02 Mg m^-3) than untracked furrows (1.22 ± 0.03 Mg m^-3). For the same depth, bulk density of ridge and shoulder positions averaged 1.36 ± 0.07 Mg m^-3 with n = 6. At probe removal differences between positions were small between tracked and untracked furrows (Table 3) . Wheel traffic increased bulk density to the 30-cm depth at Boone (Table 4) .

View this table: [in this window] [in a new window]   Table 1 Soil properties and volumetric soil water contents () at indicated matric potentials for undisturbed 7.5-cm cores of Monona silt loam at Treynor

View this table: [in this window] [in a new window]   Table 2 Soil properties and volumetric soil water contents () at indicated matric potentials for undisturbed 7.5-cm cores of Clarion loam at Boone

View this table: [in this window] [in a new window]   Table 3 Bulk density (Db) measured at probe removal and season average soil water content () by location and Depth for Monona silt loam at Treynor

View this table: [in this window] [in a new window]   Table 4 Bulk density (Db) measured at probe removal and season average soil water content () by location and depth for Clarion loam at Boone

View larger version (17K): [in this window] [in a new window]   Fig. 1 Sensor placement at Boone and Treynor sites. Ridge elevations are negative and soil depths are positive relative to furrow surface. F = furrow, R = row, SH = ridge shoulder, E = east, W = west, C = center, x = no measurement

To assess agreement among TDR measurements of for similar positions and depths, closeness of daily average between individual rows was determined for each position and depth using three comparisons:

1. The average difference (D) between the individual daily for east (_E) and west (_W) rows averaged across n values for the measurement period, given by:
   

   (1, 2)

   The standard deviation (S_D) of the difference:
   

   (2, 3)

   The root mean square error (RMSE):
   

   (3)

   
   

Similar calculations were made for the three furrows. The terms D and S_D (Gupta et al., 1984) and RMSE (Potter and Williams, 1994) are related. Since at large n, D² + S²_D is approximately equal to RMSE², RMSE can be partitioned into average difference and random error components.

	Results and discussion

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Individual Infiltration and Redistribution Events
Rows and furrows had different patterns of with time during and immediately after rainfall events as shown by sequential half-hourly measurements (Fig. 2 and 3) and by the change in expressed as the difference in relative to the fixed antecedent condition at each measurement location just before the start of a specified rainfall event (Fig. 4 and 5) . These changes and patterns of with time indicate that the main infiltration and downward water movement occurred in furrows, with delayed lateral movement to row positions. Observations during probe installation, limited disk permeameter measurements (data not shown), and the rapid vertical movement of the wetting front to the 60-cm depth at Boone and 90-cm depth at Treynor under untracked C furrows indicate that downward water movement may have been enhanced by macropore flow at both sites (Fig. 2, 4A, 4B, and 6) .

View larger version (51K): [in this window] [in a new window]   Fig. 2 Soil water content measured at half-hour intervals for east, center, and west furrows at Treynor for DOY 184 through 185. Rainfall amount (PPT) is shown on lower axis. Depth is relative to furrow surface

View larger version (48K): [in this window] [in a new window]   Fig. 3 Soil water content measured at half-hour intervals for east and west rows at Treynor for DOY 184 through 185. Rainfall amount (PPT) is shown on lower axis. Depth is relative to furrow surface

View larger version (58K): [in this window] [in a new window]   Fig. 4 Increase in volumetric soil water content (), compared with antecedent measured 1 h before start of rainfall, under ridges and furrows at indicated elapsed time in hours following start of rainfall events of 34 mm at Boone (0250–0950 h) and 21 mm at Treynor (0035–0845) on DOY 184

View larger version (69K): [in this window] [in a new window]   Fig. 5 Increase in volumetric soil water content (), compared with antecedent measured 1 h before start of rainfall, under ridges and furrows at time indicated following 22 mm rainfall ending 0555 h DOY 220 at Treynor

View larger version (40K): [in this window] [in a new window]   Fig. 6 Soil water content measured at half-hour intervals for east, west, and center furrows at Boone for DOY 184 to 185. Rainfall amount (PPT) is shown on lower axis. Depth is relative to the furrow surface

Treynor
On DOY 184, within 1.5 h of two rainfall events (5 mm in 30 min starting at 0035 h followed by 16.5 mm in 1 h starting 0745 h), _max > 0.07 m³ m^-3 to 60 cm in the C furrow, while the W furrow _max > 0.03 m³ m^-3 to the 60-cm depth and E furrow _max > 0.05 m³ m^-3 to the 45-cm depth within 2.5 h (Fig. 2). By 1240 h, or 5 h after the start of the second rain event, was decreasing in the C furrow at all depths <90 cm (Fig. 2B) but was slowly increasing across the 15- to 60-cm depth in E and W rows (Fig. 3). At this time, was 2% or less in the row from the 5- to 90-cm depths (Fig. 3 and 4B). In the row position, the wetting front moved <10 cm vertically below the soil surface during DOY 184 and 185. At the -6-cm row depth (5 cm below row surface), increased 0.04 m³ m^-3 by 1100 h, but no increase in was measured at the -1-cm row depth (10 cm below row surface) and was <0.01 m³ m^-3 at the 5-cm row depth (same elevation as 5-cm furrow depth) until DOY 185 (Fig. 3).

Both Sites
Comparisons
During rainfall events, ridge shoulders had large , presumably due to low bulk density, greater evaporation, and concentration of runoff from ridge surfaces (Fig. 4A and 4B). At the same elevation, for row positions lagged furrow positions at both sites. There was a distinct lag in for row positions compared with furrow positions following rainfall on DOY 184 at Treynor (Fig. 2 and 3). This was in part due to additional distance of travel for water infiltrating in the ridge, runoff from the ridge, and the large increases in in ridge and shoulder positions.

_max Comparisons
On DOY 184 at Treynor, _max was smaller for row positions than for furrow positions (Fig. 2 and 3). The lag and smaller amplitude of _max for the 5- and 15-cm row depths relative to 5- and 15-cm furrow depths occurred with most rainfall events. The _max for 5- and 15- cm furrow depths at Treynor was closely related to initial (_initial):

(4)

but _max and _initial were not significantly correlated for the same row depths even though the average _initial of the two rows and three furrows were similar for individual depths (Fig. 7) . At Boone, _max for 5- and 15-cm furrow depths was also related to _initial:

(5)

View larger version (31K): [in this window] [in a new window]   Fig. 7 Average of time domain reflectometry–measured soil water content for three furrows and two rows at maximum time for redistribution immediately before next rainfall event at Treynor in 1992. Error bars = ±1 SE

View this table: [in this window] [in a new window]   Table 5 Relationship of maximum soil water content increases (max) in rows to (max) in furrows

Wheel Traffic Effects
At both sites on DOY 184, differences in the rate and depth of penetration of the wetting front indicates E and W tracked furrows had slower vertical water movement than the C untracked furrow (Fig. 2, 4A, 4B, and 6). The delay was especially obvious at the 90-cm depth at Treynor, where C furrow was >0.02 m³ m^-3 by 2.5 h after the start of the second rain event, but the W furrow required >24 h to reach similar (Fig. 2A and 2B). On DOY 184 at Boone, half-hourly measurements of show rapid response to initial (0300 h) rainfall to a depth of 30 cm in tracked E and W furrows and to 60 cm in the untracked C furrow (Fig. 6). Tracked furrows at Boone had greater _max at the 5-cm depth for both rainfall events than the untracked C furrow, apparently due to reduction in the rate of water movement resulting from reduced pore volume in large pores associated with greater bulk density of tracked furrows (Table 4). For 5- and 15-cm depths at Boone, the maximum for tracked furrows was at or greater than core measurements of at -1 kPa for similar bulk densities, while of the untracked C furrow was at or less than core measurements of at -10 kPa, indicating higher degree of saturation in tracked E and W furrows.

Treynor Day of the Year 220 to 245
On DOY 220 in 1992 at Treynor (Fig. 5A), averaged 0.04 m³ m^-3 greater across the 1-m profile than on DOY 184 (Fig. 4B), and the response time for row and lower furrow positions was more rapid than on DOY 184, possibly due to greater hydraulic conductivity and smaller possible _max for DOY 220 than DOY 184. At 0700 h, within 3 h of the start of rainfall on DOY 220, increased at all depths for both row and furrow positions except for the 90-cm W row position (Fig. 5A). Greatest increases in were measured 5 cm below the surface of ridge (-6-cm soil depth) and shoulder (-5-cm soil depth) positions. The initial increase in was generally greater in the furrow than at the same elevation in the row for depths below 5 cm, but following redistribution, the average increase was similar for row and both tracked and untracked furrow positions for these depths (Fig. 5B). Measured average change in (weighted by depth increment) from DOY 220 to 245 was nearly equal for row (-0.016 m³ m^-3) and furrow (-0.015 m³ m^-3) positions. On DOY 212, cumulative rainfall during the study was 185 mm, and sealing of the furrow surface by sediment from rows may have affected infiltration into furrows. The pattern of infiltration with relatively rapid response times for both row and lower furrow positions on DOY 220 was representative of infiltration events occurring on and after DOY 212 at Treynor. This pattern contrasts with slower relative response under rows following earlier rainfall events (Fig. 2, 3, and 4B) when ridges were freshly prepared and row and furrow positions had lower values.

Daily Average Soil Water Content
Time Domain Reflectometry
Average daily values of measured were also used to characterize the patterns of infiltration and recharge by depth and position. The effect of individual rainfall events, followed by redistribution and evaporation, on daily average is shown for individual furrow and row depths at Treynor (Fig. 8 and 9) . Changes in daily average due to rainfall events and differences between positions were both smaller than those observed with half-hourly measurements. For comparable times, the magnitude of changes in were generally larger in furrows (Fig. 8) than in rows (Fig. 9) at 5- and 15-cm depths, but the pattern of changes in with time (time dependencies) for furrows and rows became similar with increasing depth. The response to precipitation and redistribution was similar for the same position and depth so that nearly constant offsets were maintained over time among furrows at the same depth and between rows at the same depth. Similar results were observed at the Boone site. The similarity in response among furrows and between rows at both sites indicates that the observed effects of ridges on infiltration dominated effects due to soil variability among positions and depths.

View larger version (52K): [in this window] [in a new window]   Fig. 8 Average daily soil water content by time domain reflectometry and neutron probe measurement for furrow depth indicated and rainfall (PPT) for measurement period at Treynor. Error bars on neutron measurements = ±1 SE

View larger version (44K): [in this window] [in a new window]   Fig. 9 Average daily soil water content by time domain reflectometry and neutron probe measurement for row depth indicated and rainfall (PPT) for measurement period at Treynor. Error bars on neutron measurements = ±1 SE

(6)

View this table: [in this window] [in a new window]   Table 7 Average daily difference (D), standard deviation of the average daily difference (SD), and root mean square error (RMSE). (n = 102), for indicated row and furrow comparisons of time domain reflectometry–measured soil water content for the Boone site

Treynor Row Comparisons

Treynor Furrow Comparisons
Average daily of tracked E and W furrows were also offset up to 0.04 m³ m^-3, but followed similar trends with time, as indicated by S_D of 0.010 m³ m^-3 or less (Table 6 and Fig. 8). Untracked C and tracked W furrows comparisons had greater random error than tracked furrow comparisons at three out of four depths, reflecting the above-cited large differences in surface bulk density between tracked and untracked furrows. Agreement was poor at the 45-cm depth for the untracked center furrow vs. the average of the tracked furrow comparisons, again possibly reflecting differences in water flow due to differences in surface conditions of tracked and untracked furrows.

Profile Averages
Wheel traffic–induced differences in measurement can be inferred by comparison of profile averages of S_D, D, and RMSE (Tables 6 and 7). Both E and W rows and E and W furrows showed good agreement, as S_D for E vs. W rows averaged across 5- to 90-cm depths and S_D for E vs. W furrows averaged across 5- to 45-cm depths at Treynor was <0.007 m³ m^-3, average D was <0.018 m³ m^-3, and average RMSE was <0.02 m³ m^-3. In contrast, for comparable depths (5–45 cm), profile average S_D was greater for tracked vs. untracked furrows than for E vs. W furrows and E vs. W rows. At Treynor, the average S_D value for C vs. the average of E and W furrows (0.014 m³ m^-3) was more than two times the average S_D for E vs. W furrows, possibly due to differences in water flow properties induced by wheel traffic. Similarly, at Boone, wheel traffic affected the closeness of response of furrows (Table 7). The RMSE at Boone was generally largest for the comparison of C vs. the average of E and W furrows due to large D terms, reflecting differences in bulk density (Table 7). This comparison also had the greatest average S_D term (0.15 m³ m^-3), reflecting differences in response between tracked and untracked furrows.

Maximum Redistribution
The nine DOY shown in Fig. 7 represent profiles averaged for two rows and three furrows at the maximum time of 1 to 24 d for evaporation and redistribution (just before the next rainfall event) at Treynor. For individual depths from 15- to 90-cm, the difference between for rows and furrows remained relatively constant between DOY, even though the average increased or decreased. This indicates that between rainfall events, changes in for rows were similar in magnitude to the changes in for furrows at each depth (Fig. 7). Greatest differences in between row and furrow positions occurred at 90 cm. At the 60-cm depth, row was consistently less than furrow , presumably due to differences in bulk density between row and furrow positions.

At maximum redistribution, the average profile of rows and furrows was also closely related at both sites, demonstrating that the incremental changes in profile average between rainfall events were similar for rows and furrows (Fig. 10) . However, the change in average of rows and furrows (slope of regression of average _row with average _furrow) differed significantly (P < 0.01) for the two sites, apparently due to differences in initial conditions and soil properties governing water retention, movement, and evaporation, as suggested by differences in residue cover, bulk density, and water retention relationships between the two sites (Tables 1–4).

View larger version (27K): [in this window] [in a new window]   Fig. 10 Relationship of average soil water content of rows and furrows across profile depth of 1.0 m for Treynor and 0.75 m for Boone at maximum time for redistribution immediately before next rainfall event. Slopes of equations differed from 1:1 line. *,** Significant at the 0.05 and 0.01 levels of probability, respectively

View larger version (32K): [in this window] [in a new window]   Fig. 11 Estimated vs. measured storage calculated for the 1.0-m depth at Treynor and the 0.75-m depth at Boone

	Conclusions

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
The precision and frequency of half-hourly field TDR measurements of allowed a qualitative assessment of the direction of soil water movement between naturally occurring rainfall events and quantitative assessment of under rows and furrows over time. These were used to estimate infiltration direction and redistribution amounts between rainfall events across the measurement depth under rows and furrows. Patterns of infiltration and redistribution were less obvious from daily average measurements and were difficult to determine from weekly TDR or neutron thermalization measurements.

Across the depth of measurement, recharge was stepwise between natural rainfall events, occurring as a series of incremental increases in . Infiltration with ridge tillage did not exhibit uniform vertical frontal movement but occurred primarily in furrows, as indicated by more rapid increase in and greater _max for furrow than for equivalent row positions at soil depths <45 cm. The timing of change of profile for row and furrow positions indicated more rapid downward water movement in furrows followed by lateral soil water movement from furrow to row positions. The null hypothesis that surface configuration does not affect soil water content and movement was therefore rejected. For rainfall events >10 mm, the maximum increase in in the furrow was mainly determined by the initial . Subsequent redistribution from furrow to row positions produced the observed sequence of incremental increases in row and furrow profile between rainfall events at maximum times for redistribution. Following redistribution, rows and furrows had similar values. At both sites, there was a consistent relationship between average of rows and furrows for individual rainfall events. Consistent relationships following redistribution were maintained over time between individual row and furrow depths. Large initial increases in in near-surface ridge and shoulder positions during rainfall events, along with runoff from ridges to furrows, and additional distance of travel for water infiltrating directly into ridges, are probable explanations for reduced depth of penetration of water below the ridge surface.

At both sites, changes in measured values of daily average with time (time dependencies) for individual furrow depths were similar among the three furrows across the measurement period. The same was true for individual row depths. While the offset of up to 0.04 m³ m^-3 in measured values for different locations with the same depth and position complicates estimation of actual values for a specific location, the similarity of change in with time for the same depth and position is favorable for simulation of soil water movement with time. A more serious complication to modeling may be the apparent change with time in the relative rate of infiltration for row and furrow positions, possibly due to progressive consolidation and sealing of the furrow surface, which may require adjustment of infiltration parameters to account for changes in soil surface conditions.

The pattern of water movement associated with infiltration and redistribution for ridge-tillage appears to present the opportunity to reduce NO₃ movement by coordinating the timing of N application with plant uptake and by locating N placement at a depth under the ridge where downward water movement is least. Research results presented here apply to the period between planting and the time at which plant growth significantly affects water infiltration, loss, and movement. Additional research and model simulation is required to investigate the impact of weather, residue management, and surface geometry on water movement under growing vegetation.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Joint contribution of the Iowa Agric. and Home Econ. Exp. Stn. (Journal Paper no. J-18277, Project no. 2463) and USDA-ARS, National Soil Tilth Lab.

¹ Trade names are provided for the benefit of the reader and do not imply endorsement by Iowa State University.

Received for publication August 6, 1997.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 

• Baker J.M., Allmaras R.R. System for automating and multiplexing soil moisture measurement by time domain reflectometry. Soil Sci. Soc. Am. J. 1990;54:1-6.
• Benjamin J.G., Blaylock A.D., Brown H.J., Cruse R.M. Ridge tillage effects on simulated water and heat transport. Soil Tillage Res. 1990;18:167-180 a.
• Benjamin J.G., Ghaffarzadeh M.R., Cruse R.M. Coupled water and heat transport in ridged soils. Soil Sci. Soc. Am. J. 1990;54:963-969 b.[Abstract/Free Full Text]
• Bresler E., Kemper W.D., Hanks R.J. Infiltration, redistribution, and subsequent evaporation of water from soil as affected by wetting rate and hysteresis. Soil Sci. Soc. Am. Proc. 1969;33:832-840.
• Burrows W.C. Characterization of soil temperature distribution from various tillage-induced microreliefs. Soil Sci. Soc. Am. Proc. 1963;26:350-353.
• Clay D.E., Clay S.A., Brix-Davis K., Scholes K.A. Nitrate movement after anhydrous ammonia application in a ridge tillage system. J. Environ. Qual. 1994;23:9-13.
• Clay S.A., Clay D.E., Koskinen W.C., Malzer G.L. Agrichemical placement impacts on alachlor and nitrate movement through soil in a ridge tillage system. J. Environ. Sci. Health. B 1992;27(2):128-138.
• Gardner W.H. Water content. In: Klute A., ed. Methods of soil analysis. Part 1. 2nd ed. Agron. Monogr. 9. Madison, WI: ASA and SSSA, 1986:493-544.
• Gupta S.C., Larson W.E., Allmaras R.R. Predicting soil temperature and soil heat flux under different tillage-surface residue conditions. Soil Soc. Am. J. 1984;48:223-232.[Abstract/Free Full Text]
• Hamlett J.M., Baker J.B., Horton R. Water and anion movement under ridge tillage: A field study. Trans. ASAE. 1990;33:1859-1866.
• Hillel D. Applications of soil physics. New York: Academic Press, 1980.
• Horton R., Allmaras R.R., Cruse R.M. Tillage and compactive effects on soil hydraulic properties and water flow. In: Larson W.E., et al. , ed. Mechanics and related properties in structured agricultural soils. Dordrecht, the Netherlands: Kluwer Academic Publ, 1989:187-203.
• Jaynes D.B., Swan J.B. Solute movement in a fallow ridge tillage system under natural rainfall. Soil Sci. Soc. Am. J. 1999;63:264-269.[Abstract/Free Full Text]
• Kemper W.D., Olsen J., Hodgson A. Fertilizer or salt leaching as affected by surface shaping and placement of fertilizer and irrigation water. Soil Sci. Soc. Am. Proc. 1975;39:115-119.
• Laflen J.M., Amemiya M., Hintz E.A. Measuring crop residue cover. J. Soil Water Conserv. 1981;36:341-343.
• Potter K.N., Williams J.R. Predicting daily mean soil temperatures in the EPIC simulation model. Agron. J. 1994;86:1006-1011.[Abstract/Free Full Text]
• Radke J.K. Managing early season soil temperatures in the Northern Corn Belt using configured soil surfaces and mulches. Soil Sci. Soc. Am. J. 1982;46:1067-1071.[Abstract/Free Full Text]
• Shaw R.H., Buchele W.F. The effect of the shape of the soil surface profile on soil temperature and moisture. Iowa State College J. Sci. 1957;32:95-104.

This article has been cited by other articles:

				J.F. Power, R. Wiese, and D. Flowerday Managing Farming Systems for Nitrate Control: A Research Review from Management Systems Evaluation Areas J. Environ. Qual., November 1, 2001; 30(6): 1866 - 1880. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Bargar, B. Articles by Jaynes, D. Search for Related Content PubMed Articles by Bargar, B. Articles by Jaynes, D. Agricola Articles by Bargar, B. Articles by Jaynes, D.