Plant and Soil 237: 25–35, 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Soil water dynamics in row and interrow positions in soybean (Glycine
, Yakov Pachepsky
& Vangimalla R. Reddy
USDA/ARS Alternate Crops and Systems Laboratory, Bldg 007, Rm 116, BARC-W, Beltsville, MD 20705, USA.
USDA/ARS Hydrology and Remote Sensing Laboratory, Bldg 007, Rm 104, 10300 Baltimore Ave., Beltsville, MD
Received 28 November 2000. Accepted in revised form 19 July 2001
Key words: plant canopy, stemﬂow, throughfall, time domain reﬂectometry
Quantitative knowledge of inﬁltration processes and the mechanisms that control water movement in soil is
necessary to properly manage water and chemical use in agricultural ﬁelds. The objective of this study was to
compare the soil water content dynamics in row and interrow positions in a soybean crop (Glycine max L.) under
conventional (plow) tillage. Two ﬁeld plots (Beltsville silt loam soil, Fine-loamy mixed mesic Typic Fragiudult)
were instrumented with Time Domain Reﬂectometry (TDR) probes at 0–10 cm, 0–25 cm and 0–40 cm depths.
TDR probes were installed in the row and interrow positions. Soil water content was continuously monitored at
1 hour intervals. The distribution of inﬁltrated water and evapotranspiration showed strong row-interrow patterns.
The row positions received signiﬁcantly more water during precipitation than the interrow positions. Water loss,
due to evapotranspiration, was also signiﬁcantly greater in the row position than in the interrow position. Both
plant and soil characteristics appeared to be important factors for inﬁltration and redistribution. The results of this
study suggested that the presence of the crop canopy altered the surface boundary conditions of the soil and, hence,
the volume of inﬁltrating water. Results of this study suggest that in order to model water movement in row crops,
the ability to simulate canopy architecture and ﬂow processes in two dimensions is necessary.
The practice of planting agricultural crops in rows res-
ults in the potential for large variations in water and
solute transport, and distributions with respect to dis-
tance from the plant stem. The crop canopy intercepts
rainfall and changes the intensity, amount and distribu-
tion of water that reaches the ground (Haynes, 1940).
McGregor and Mutchler (1982) reported that the num-
ber of raindrops per unit area under a corn plant (Zea
mays L.) decreased with increase in canopy, but me-
dian drop sizes were larger under the canopy than in
the open midrow area. Water droplets cascading from
leaf to leaf at the outer boundary of the canopy grow in
size due to aggregation of smaller raindrops although
the velocity is decreased (Kitanosono, 1972; Morgan,
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1985). Haynes (1940) reported that the amount of rain
(throughfall) passing through the canopy (other than
water ﬂowing down the stem) and reaching the ground
in row crops was greatest in the mid-row position. The
amount of throughfall decreased toward the stem.
Armstrong and Mitchell (1987) found a linear re-
lationship to ground rainfall as a function of distance
from stem for both corn and soybean (Glycine max
L.). Intercepted rain may also be directed toward
the plant and reach the ground as stemﬂow in most
crops (Bui and Box, 1992; Haynes, 1940; Quinn and
Laﬂen, 1983). Up to 47% of rainfall arriving at the
soil as stemﬂow has been reported for corn (Quinn and
Laﬂen, 1983) and 30% for soybean (Haynes, 1940).
The magnitude of stemﬂow and canopy throughﬂow
depends on the stage of growth and rainfall rate.
Throughﬂow remains fairly constant until about 50%
crop cover is reached in corn and 35% in soybean