Vol.4, No.10, 521-528 (2013) Agricultural Sciences
http://dx.doi.org/10.4236/as.2013.410070
Root zone soil moisture redistribution in maize (Zea
mays L.) under different water application regimes
John Mthandi1*, Fedrick C. Kahimba1, Andrew K. P. R. Tarimo1, Baandah A. Salim1,
Maxon W. Lowole2
1Department of Agricultural Engineering and Land Planning, Sokoine University of Agriculture, Morogoro, Tanzania;
*Corresponding Author:
2Department of Crop Science, Bunda College of Agriculture, Lilongwe, Malawi
Received 26 June 2013; revised 26 July 2013; accepted 1 August 2013
Copyright © 2013 John Mthandi et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Soil moisture availability to plant roots is very
important for crop growth. When soil moisture
is not available in the root zone, plants wilt and
yield is reduced. Adequate knowledge of the
distribution of soil moisture within crop’s root
zone and its linkage to the amount of water ap-
plied is very important as it assist s in optimising
the efficient use of water and reducing yield loss-
es. The study aimed at evaluating the spatial
re dis tribution of soil moisture within maize roots
zone under different irrigation water application
regimes. The study was conducted during two
irrigat ation season s of 20 12 at Nkango Irrigation
Scheme, Malawi. The trials consisted of fa ctori al
arrangement in a Randomised Complete Block
Design (RCBD). The factors were water and ni-
troge n and both were at four levels. The Triscan
Sensor was used to measure volumetric soil mo-
isture contents at different vertical and lateral
points. The st udy inferred tha t th e de g ree of soil
moisture loss depends on the amount of water
present in the soil. The rate of soil moisture loss
in 100% of full water requirement regime (100%
FWRR) treatment was higher than that in 40%
FWRR treatment. This was particularly noticed
when maize leaves were dry. In 100% FWRR
treatment, the attraction between water and the
surfaces of soil particles was not tight and as
such “free” water was lost through evaporation
and deep percolation, while in 40% FWRR, water
was strongly attracted to and held on the soil
particles surfaces and as such its potential of
losing water was reduced.
Keywords: Soil Moisture Content; Full Crop Water
Requirement Regime; Maize Root Zon e
1. INTRODUCTION
Water use efficiency and water productivity are im-
portant agricultural performance indicators that are used
in assessing the impact of water management practices
that are used to produce more crops with less water [1].
It is vital to specify the water use components when de-
riving water use efficiency and productivity to avoid the
confusion over the two, since these terms are related, but
are not essentially the same [2].
In irrigation engineering terms water use efficiency is
defined as the ratio between amount of water required to
grow a crop (i.e. evapotranspiration, percolation and see-
page, leaching for salinity control, and land preparation),
and the total amount of water applied in irrigation sink
or within a spatial domain of interest [2]. Water use effi-
ciency (WUE) as an agronomic term means the ratio be-
tween marketable crop yield and amount of water stored
in the root zone that is only up-taken and transpired by
the crop [3]. Under agronomic definition of water use
efficiency, amount of water stored within the crop root
zone but lost through evaporation is not accounted for
[4]. Irrigation engineering and agronomic water use ef-
ficiencies may be related to each other but under nor-
mal circumstances increase in irrigation engineering wa-
ter use efficiency does not result in an increase in agrono-
mic water use efficiency. For example, in Irrigation engi-
neering water use efficiency is directly correlated with de-
crease in applied water. But this does not mean that re-
duced amount of water will result in an increase in crop
yield. This is because less amount of applied water may
not have the ability to flush out salts or may not be enough
to meet the demand of the crops hence low yield may oc-
cur meaning that agronomic water use efficiency is low.
The ambiguity in the definitions and interpretation of wa-

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528
522
ter use efficiency has resulted in the introduction of water
productivity replacing agronomic water use efficiency [5].
Water Productivity (WP) is defined as a ratio of unit
of yield produced to unit volume of water used to pro-
duce the yield [6]. When water is in short supply, the WP
is substantially increased through deficit irrigation. [7,8]
reported that in several situations, the 50% depletion level
of available soil moisture is the critical point of many
soils beyond which yields were reduced. On the other
hand, the 50% - 60% replacement of total crop water re-
quirements was found as the critical range in which WP
realises acceptable yields under deficit irrigation [9,10].
Agronomically the 50% - 60% depletion of readily avai-
lable water corresponds to the threshold for leaf expan-
sion [11]. Soil moisture availability to plant roots is very
important for crop growth. When soil moisture is not
available in the root zone, plants wilt and yield is re-
duced. [12] reported that status, availability and distri-
bution of soil moisture within a root zone of crop affect
the growth and yield of crops. When crop roots are using
less energy to extract water from the soil, the saved ener-
gy is converted into yield and this increases water pro-
ductivity [13]. When crop roots are having difficulties in
extracting water from the soil, the plant is stressed and
this is manifested through decrease in leaf area growth
which limits the ability of leaves to absorb sunlight and
transpire water resulting in less crop yield.
Adequate knowledge of the distribution of soil mois-
ture within crop’s root zone and its linkage to the amount
of water applied is very important as it will optimise the
efficient use of water and reduce yield losses. The aim of
this study was to evaluate the spatial redistribution of
soil moisture within maize roots zone under different ir-
rigation water application regimes.
2. MATERIALS AND METHODS
2.1. Site Description
The research study was done at Nkango Irrigation
Scheme in Kasungu district. Data were taken in two
irrigation growing seasons from 1st June to 8th September,
2012 during the first season,and from 10th September to
5th December, 2012 during the second season. Nkango
Irrigation Scheme is an informal scheme which is owned
and managed by the local communities and is situated at
Latitude 12˚35’ South and Longitudes 33˚31’ East and is
at 1186 m above mean sea level. The study area has a
unimodal type of rainfall with rains between December
and April. The mean annual rainfall is about 800 mm.
The site lies within maize production zone of Malawi
and has dominant soil type of coarse sandy loam. Small-
holder farmers in the area practise irrigation and are
conversant with water application regimes.
The soil of the plots is sandy loam with a low soil
organic matter and nutrient concentration as described in
Table 1. Characteristics of the top soil (0 - 20 cm) of at the
research site in Nkango, Malawi.
Soil properties Values
Clay (%) 13
Silt (%) 17
Sand (%) 70
Carbon (%) 0.599
C/N ratio 13.011
OM (%) 1.0773
Total nitrogen (%) 0.046
Total phosphorus (ppm) 33.206
Total potassium (µeq·K·g−1) 1.2153
Exchangeable calcium (µeq·K·g−1) 19.254
Exchangeable magnesium (µeq·K·g−1) 28.964
Moisture content (%) 4.163
Field capacity (%) 20
Wilting capacity (%) 10
Bulk density (g/cm3) 1.59
pH 5.2
Ta ble 1. The Cation Exchange Capacity is low (50.00 -
80.00 µeq·g−1), and the pH decreased from acidic (5.2)
to strongly acidic (4.7). The salinity of the soil was very
low (1.7 mmhos/cm).
2.2. Experimental Design
The plot size was 5 m by 5 m and ridges were spaced
at 75 cm. The plots were separated from one another by
a 2-metre boundary to avoid “sharing” of responses, wa-
ter and nitrogen (edge effects). Three maize seeds of hy-
brid maize (SC 407) were planted per hole at plantspac-
ing of 25 cm and row spacing of 75 cm. They were later on
thinned to one seed per station 7 days after germination.
The trials consisted of factorial arrangement in a Ran-
domised Complete Block Design (RCBD). The factors
were water and nitrogen, and both were at four levels.
Water had four application regimes and these were as
follows: farmers’ practice regime (contol); full (100%)
water requirement regime (FWRR) of maize plant; 60%
of FWRR; and 40% of FWRR. A full maize water re-
quirement was determined by using the procudure des-
cribed in [14]. Nitrogen had four application regimes
and these were as follows: The Typical Nitrogen Appli-
cation Rate in the area (TNPRA) of 92 kg N/ha was used
as a basis (control) to determine other dosage levels in
the study [15]. The nitrogen dosage levels were as fol-
lows: TNPRA, 92 kg N/ha; 125% of TNPRA, 115 kg
N/ha; 75% of TNPRA, 69 kg N/ha; and 50% of TNPRA,
46 kg N/ha.
2.3. Data Collection
The Triscan Sensor (EnviroScan, Sentek Pty Ltd.,

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528 523
Stepney, Australia), which has ability to sensor volu-
metric soil moisture at the instant time of inserting the
monitoring probe in the soil, was used to measure soil
moisture content at different points (defined by lateral
and vertical distances) within maize root zone depth.
The lateral distances were at interval of 5 cm as shown
in Figure 1. The measured points were: at point of ferti-
lizer application (represented by 0 cm, which is 10 cm
from the plant), at 5 cm away from the plant (represent-
ed by −5 cm), at 5 cm towards the plant, 10 cm towards
the plant (this point was maize planting station), and 15
cm (this point was 5 cm after planting station) as shown
in Figure 1. The lateral distances were taken based on
spreading and elongation pattern of lateral roots of maize
plants. The lateral readings of nitrogen were respectively
taken at five soil depths of 20, 40, 60, 80, and 100 cm
from the soil surface,and were selected based on maize
roots growth habits, which extend down to 100 cm [16].
2.4. Data Analysis
The data presented in this paper were from treatment
combinations of 100% of FWRR and 92 N Kg/Ha and
40% of FWRR and 92 N Kg/Ha. This is because statis-
tically treatment combination of 100% of FWRR and 92
N Kg/Ha gave the highest nitrogen use efficiency and
40% of FWRR and 92 N Kg/Hagave the highest water
Figure 1. Showing measurement points.
productivities. The data are presented in graphical form
to indicate comparative redistribution of soil moisture
content in both treatment combinations.
3. RESULTS AND DISCUSSIONS
Figures 2 and 3 indicate the spatial distribution of soil
moisture on 10th July in maize plots of 100% FWRR and
40% FWRR respectively. The figures indicate that at
point where maize was planted, the soil moisture was
high at 20 cm in 40% than in 100%, while at 40 cm deep
Figure 2. Soil moisture content distribution in 100% FWRR on
10 July.
Figure 3. Soil moisture content distribution in 40% FWRR on
10 July.

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528
524
soil moisture content was high in 100% FWRR than in
40% FWRR treatments. At 60 cm, the soil moisture was
very high in 100% FWRR and was about 27% while in
40% FWRR, the soil moisture was about 18%. At 100
cm below, the soil moisture contents were relatively the
same in both plots of 100% FWRR and 40% FWRR.
The general observations indicate that at 20 cm below,
there was negligible difference of soil moisture contents
in both treatments.Higher soil moisture contents were
observed from 40 cm, 60 cm to 80 cm. At 100 cm neg-
ligible differences were again observed in both treat-
ments. The reason to this observation is that at shallow
soil depths soil water loss through evaporation is propor-
tional to the degree of soil wetness, i.e. moist surface
loose high amount of water than less moist surfaces due
latent heat which is absorbed by soil water and hence
subjecting the surface to more water loss. Over the period,
the surface will relatively have the same moisture con-
tents. On 10th July, maize plants were almost 40 days
after planting and the leaves were not fully developed to
completely shade the land surface, as such during this
period water loss through evaporation was high.
Between 20 and 80 cm deep the differences in soil
moisture content may be due to uptake by maize roots.
In 40% FWRR, the plants roots are stressed and have
less ability to attract water from the surrounding areas.
In 100% FWRR, the surrounding soil has high moisture
contents due to applied water but also due to ability of
plant roots to attract water from the surrounding areas.
At the depth of 100 cm, the soil moisture contents may
entirely be due to not being uptaken by maize roots.
Several studies have shown that soil moisture increases
with depth. It is unlikely that on 20th July, water through
deep percolation may have greatly attributed to the
changes of soil moisture at 100 cm in both treatments.
Figures 4 and 5 show that spatial distribution of soil
moisture contents at 20 cm deep in both treatments had
similar pattern and they all spread with 15% to 25% soil
moisture contents. Big differences of spreading patterns
were observed in at 40 cm below. At 60 cm below the
distribution had similar pattern with the lowest figures at
lateral distance of 10 cm and highest at 0 cm. At 100 cm
below, soil moisture though similar distribution pattern
in both treatments, but the figures in 100% FWRR treat-
ment were much higher than those in 40% treatment.
The high differences at 60 cm may be due to absorption
of water by maize roots and this can be substantiated by
a low figure at lateral distance of 10 cm which was at the
point of maize seeds plantation. Many studies on maize
roots behaviour suggests that maize roots tend to grow to
100 cm, but during flowering stages, maize roots are
more active at depth between 50 to 70 cm below and this
study suggest that rate of water absorption was very high
within this soil depths. At 100 cm below soil moisture
increase in 100% FWRR treatment may be due to deep
percolation of water from the applied water. On 20th July
the maize plant had reached 50 days after planting. The
plant leaves had fully developed with leaf area index at
its highest, and during this period land surface is wholly
covered by leaves resulting in less evaporation and high
downward movement of water as there is less competing
force.
Figures 6 and 7 indicate the spatial distribution of soil
moisture on 30th July when the maize was 60 days after
planting old. The behaviour of soil moisture contents at
Figure 4. Soil moisture content distribution in 100% FWRR on
20 July.
Figure 5. Soil moisture content distribution in 40% FWRR on
20 July.

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528 525
Figure 6. Soil moisture content distribution in 100% FWRR on
30 July.
Figure 7. Soil moisture content distribution in 40% FWRR on
30 July.
20 cm in both treatments suggests increase in all plants
as compared to previous points i.e. the measured points
at 20 cm have more soil moisture contents than those
measured before. At 40 cm, huge differences are noted in
40% FWRR treatment where at lateral distance of −5 cm,
the content of soil moisture was lowest followed by at 10
cm. This period due to development of leaves there are
less evaporation losses but transpiration losses have in-
creased meaning that the ability of maize roots to absorb
soil water has increased, hence the negative gradient of
water has been created around maize roots.
The stressed roots tend to grow towards the regions
where there is water. This situation has made water to
move from surrounding areas to the areas next to plant
roots. The decrease in losses through evaporation has
made the surface soil to have high moisture content than
before.
On 9th August, when the maize plant was 70 days old,
Figures 8 and 9 indicate the high variations in the spatial
distribution of soil moisture. At 20 cm below, the dis-
tribution of moisture is in both treatments spread out
within 20 to 25%, at 40 cm below there is high variation
Figure 8. Soil moisture content distribution in 100% FWRR on
9 August.
Figure 9. Soil moisture content distribution in 40% FWRR on
9 August.

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528
526
of moisture distribution i.e. spread out from 22 at 15 cm
to 32% at −5 cm in 100% FWRR treatment while in
40% FWRR treatment the distribution is spread within
25 at −5 cm to 27% at 0 cm, the small difference at 40
cm in 40% FWRR shows that there was less water ab-
sorption activity which would have resulted in some
points having less moisture content due to absorption
than other points. In 100% FWRR treatment, the high
variations of soil moisture contents indicates that some
points were being absorbed than other points for example
at the lateral distances of 15 cm, 5 cm, and 0 cm more
water was being absorbed than at 5 cm away from the
plants (−5 cm) which had high value of 32%. At 60 cm
below, in 40% FWRR treatment we are now start to see-
ing an increase in variations of soil moisture distribu-
tions which ranged from 24% at 0 cm to 28% at 10 cm,
and the increase in variations of soil moisture has con-
tinued to increase at 80 cm from 26% at 10 cm to 31% at
15 cm, and at 100 cm the variations has further increased
from 24% at 10 cm to 31% at 0 cm. The general trend of
spatial soil moisture distribution in 40% FWRR treat-
ment is that is declining while in 100% treatment the
trend of spatial moisture distribution is increasing but the
variations of moisture distribution from 60 cm in de-
creasing. The differences may be attributed to the fact
that maize roots in 40% FWRR treatment have grown
longer and are able to tap soil water at lower depth of 60
cm to 100 cm while the maize roots in 100% FWRR have
not developed progressively to actively tap water at low-
er depths. The roots develop in respond to degree of wa-
ter availability, when soil water is scarce the plant roots
develop surviving strategy of long roots so that it can tap
water at lower depths but when soil moisture is available
plant roots will convert the energy saved into yield and
roots do not grow longer.
Figures 10 and 11 show that the general trend of mo-
isture contents at all points in both treatments is de-
creasing when compared with the trend of Figures 8 and
9 on 9 August. Specific observations indicate that the
variations of moisture contents in 40% FWRR treat-
ment started at 60 cm than in 100% FWRR treatment.
On 19 August, the maize plant was 80 days old and dur-
ing this late stage most of the lower leaves of maize
plants have dried exposing ground surface to evapora-
tion which has increased due to high temperature. The
evaporation made the soils to loss more water. However,
the maize is still absorbing water because plant is still lo-
sing water through transpiration stream and this is crea-
ting demand of more water in the plants.
Figures 12 and 13, on 29th August, the maize plant
was 90 days old and all the leaves in both treatments
have dried and are no longer losing water through trans-
piration. The dying of leaves though has exposed the soil
surface and water is being lost through evaporation.
Figure 10. Soil moisture content distribution in 100% FWRR
on 19 August.
However, of interest is the rate of soil water loss, if
compared with figures of 10 and 11 it shows that Figure
12 of 100% FWRR treatment has lost more water within
the same period than that of 40% FWRR treatment. For
example, at 100 cm below of Figure 11 (100% FWRR),
at point 15 cm has lost moisture from 37% on 19 August
to 28% on 29 August, yet during the same period of 10
days and the same depth 100 cm in 40% FWRR treat-
ment, the similar point (15 cm) has moisture from 24%
on 19th August to 21%. This shows that the soil that has
high moisture content loses more water than soil that has
less moisture content. One of the reason is that there is
loose water that is freely moving within soil pores and
therefore less energy from the sun is required to eva-
porate them but in soil that have less water, water is held
tightly together and more energy is required to evaporate
them.
On 8th September, the maize plant was 100 days old
and the maize including the cobs have completely dried.
The maize was harvested on this day. The spatial mois-
ture content distribution in Figures 14 and 15 indicated
shows that there is huge decline of soil moisture content
at the shallow depth of 20 cm in both treatments as com-
pared to lower depths.
4. CONCLUSION
In this study, we infer that the degree of soil moisture
loss depends on the amount of water present in the soil.
The rate of soil moisture loss in 100% FWRR treatment
was higher than that in 40% FWRR treatment. This was
particularly noticed when maize leaves were dry. In
100% FWRR treatment, the attraction between water

J. Mthandi et al. / Agricultural Sciences 4 (2013) 52 1-528 527
Figure 11. Soil moisture content distribution in 40% FWRR on
19 August.
Figure 12. Soil moisture content distribution in 100% FWRR
on 29 August.
and the surfaces of soil particles was not tight and as
such “free” water was lost through evaporation and deep
percolation, while in 40% FWRR, water was strongly
attracted to and held on the soil particles surfaces and as
such its potential of losing water was reduced.
The soil moisture redistribution in the root zone is di-
rectly related to the amount of applied irrigation water
and spatial distribution of soil moisture content was pri-
marily influenced by roots water uptake and evaporation.
Evaporation was critical especially before leaves were
fully developed and after the leaves have dried.
Figure 13. Soil moisture content distribution in 40% FWRR on
29 August.
Figure 14. Soil moisture content distribution in 100% FWRR
on 8 September.
Soil loss through deep percolation was high in 100%
FWRR. When the soil moisture content is optimal for plant
growth, the water in the large- and intermediate-sized
pores can easily move about in the soil which can result
in a deep percolation.
The redistribution patterns of soil moisture in both
treatments were similar. However in 100% FWRR, the
measured points had higher soil moisture contents than
that in 40% FWRR treatment and soil water has fluxed
to deeper layers, while in 40% FWRR, soil moisture was
only concentrated in the top layers of the soil and this re-
stricted water uptake by plants roots in deeper layers.

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OPEN A CCESS