沙漠研究 22-1, 243 -246 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－

Terrace Development Applied as a Water Harvesting Technologyfor Stable NERICA Production in Uganda
Akio GOTO*1), Ryuzo NISHIMAKI2), Shinji SUZUKI3), Fumio WATANABE3) and Satoru TAKAHASHI3)
Abstract: In Uganda, the greatest cause of crop damage is the shortage of rainfall due to meteorological and land structural aspects
of present farming situation. The purpose of this study was to evaluate the effect of terrace development, the relationship between
terrace size and efficiency of rainfall catchment, and the subsequent effects of terrace development on rice yield of the New Rice for
Africa (NERICA) on sloping rainfed fields. Results revealed that terrace developments were efficient in terms of rainfall catchment
which led subsequent effects on the increase of volumetric water contents and rice yield. It is suggested that narrow sized terraces are
more efficient than wide sized terraces in rainfall catchment since the highest average yields of 1,568 and 1,237 Kg/ha were recorded
for 0.9 m and 1.5 m terraces, respectively, while the 2.5 m terrace and non-terraced control had the least yields of 1,038 and 777 Kg/harespectively. In addition, the average increasing rate in volumetric water content after rainfall was four times higher for banked
terraces than in non-terrace plots. It was also revealed that terrace development decrease the number of missing rice plants byreducing the influence of soil erosion at inclined fields. The above study highlights that terracing is an effective water harvest
technology for stable NERICA production under certain levels of unexpected and inexplicable changes in the rainfall pattern.
However, because the use of terraces can prove futile in cases of severe drought, they must be applied alongside other technologies likeirrigation.
Key Words: NERICA, Republic of Uganda, Technology, Terrace Development, Water Harvesting

1. Introduction
The Republic of Uganda has very favorable climaticconditions for Agriculture, notably because of bimodal rainfall
pattern characterized by average annual precipitation above
1,200 mm, and average annual temperature ranging from 20.5
to 30.0 Degrees Celsius. In spite of the country’s location onthe equator, a majority of farmlands are at altitudes of over
1,000 meters above sea level. However there are various
constraints in micro aspects such as 96.2% farmlands
categorized as rainfed field and 53.1% are located on slopesthat have inefficient rainfall utilization and proneness to soil
erosion. In recent years, NERICA (New Rice for Africa)
cultivation area has expanded in Uganda because of its
liquidity and easy innovation by poor rural farmers in spite its
high depletion of moisture content for growth compared withthat of other upland crops. NERICA is a new group ofupland rice varieties that is the product of interspecifichybridization between high yield-potential Asian species andAfrican species that are resistant to diseases. There are 3NERICA varieties are released in Uganda. The Governmentof Uganda has ranked rice as one of the important crops in its
Development Strategy and Investment Plan (DSIP) from 2009

- 2014 being implemented by the Ministry of Agriculture,
Animal Industries and Fisheries (MAAIF).
However,
productivity has not been as high as expected due to the factthat most parts of Uganda are experiencing high erratic rainfallpatterns, long-dry spells and difficulty at inclined fields thathave culminated in varying degrees of crop losses.
In view of the above meteorological and land structural
aspects, there is a necessity of developing water harvesting
technologies that can be adopted by farmers to ensure stable
NERICA production on undulating inclined fields.
Therefore, this study evaluated the relationship between
terrace size and efficiency of rainfall catchment, and thesubsequent effects of terrace development on NERICA rice
yield when cultivated on inclined rainfed fields in Uganda.

2. Materials and Methods
2.1 Field location
Field studies were conducted at the rice researchexperiment fields of the National Crops Resources ResearchInstitute (N: 00º30’46.4, E: 32º38’03.6, 1120 m alt.) underNational Agricultural Research Organisation in Uganda (Fig. 1)
during 2007B - 2010A (A and B after years stands for the 1st
rainy season and 2nd rainy season respectively).

*Corresponding Author: nacrri-jica@live.jp
1-1-1, Sakuragaoka, Setagaya-ku, Tokyo, 156-8502, Japan
1) Graduate School of Agriculture, Tokyo University of Agriculture, Japan2) Japan International Cooperation Agency, Japan3) Faculty of Regional Environment Science, Tokyo university of Agriculture, Japan

in Uganda. Yield survey was conducted at physiologicalmaturity using yield components to determine rice yield perhectare.

Fig. 1. Location of experimental site at National Crops Resources
Research Institute (NaCRRI) in Uganda

2.4 Terrace development and Rice yield
In 2007B and 2008A, the efficiency of rainfall catchment
and subsequent effect of terracing on the yield of NERICA-4
was assessed using different terrace sizes, 0.9, 1.5, and 2.5 m
respectively. The terrace treatments were replicated 3 timesin 2007B and 4 times in 2008A.
In 2009A and 2009B, the shapes of the terraces weremodified by banking with soil alone (Fig. 3) and withsoil-filled sacks (Fig. 4) since terraces developed in 2008A
were not able to restrain run-off water of rainfall. The
experiment was replicated 7 times.
In 2010A, 2 sized terraces namely 2.5 m and 5 m bothbanked with soil only experimented in comparison to control
to further confirm the effect of rainfall catchment on yield.
The experiment was replicated 4 times.

Fig. 2. Experimental design and treatment allocation.
Theexperimental field was divided lengthways and treatments wereset within each plot without randomization.

2.2 Experimental design and Treatment allocation
Terraces were developed on a field inclined at 10 degrees.
During terrace development, top soil was initially removed
aside and put back after terraces were developed to ensure theeven distribution of nutrient-rich topsoil on each terrace.
The experimental plots were arranged across the slope
gradient without randomization, otherwise treatments could
influence each other with regards to the amount of run-offwater.
The control (non-terraced) plots were locatedalongside treatment plots, so that run-off water from the control
would not affect results of treatments in the lower parts of theslope. Since the experiment was aimed at assessing theefficiency of rainfall catchment by different sized terraces, thefield was initially divided lengthways and treatments wereassigned within each plot (Fig. 2).
2.3 Cultivar and Yield survey method
The cultivar used for the experiments was NERICA-4
which is the most widely adopted and stable upland rice variety

Fig. 3. 2.5m-Terrace banked with soil (left) and control (right)
during a downpour. Terraces retain rainfall but water escapes
down the control field.

Fig.4. Terraces banked with soil-filled sacks.

Fig. 5. Movement of volumetric water contents at terraces andno-terrace.
Table 1. Total rainfall (mm) in each season. Season A and B standfor March to July and September to January, respectively.

YearSeason A
Season B

2007
439.9
552.3

2008
543.1
591.3

2009
289.7
511.4

2010
566.1

The analyses were performed using F-test followed byT-test in Microsoft Excel to know statistical reliability.
2.5. Measurements of Volumetric Water Contents andRice yield
In 2009A and 2009B, the variations of Volumetric Water
Contents (hereinafter VWC) in the 15 cm soil-depth weremonitored using soil moisture sensors (EC-5, Decagon
Devices Inc., Pullman, WA, USA) and data loggers (Em50,Decagon Devices Inc., Pullman, WA, USA). The equipment
was set to automatically collect VWC data on an hourlyinterval at 2 types of terraces in comparison to control (Fig. 5).
In addition, VWC data immediately after receiving rainfall
were surveyed and evaluated (Table 1).
2.6. Terracing size and Number of existing rice plants
In 2010A, the number of existing rice plants in 3 m length
in row was counted with 2 replications to ascertain the degreeof soil erosion in each treatment. The data is analyzed using
mean difference t-test probability to know statistical reliability.

3. Results and Discussions
3.1. Effect of terrace development and its size on rice yield
The total rainfall was adequate in both seasons as 552 mmand 543 mm for 2007B and 2008A, respectively (Table 1).
Results of terrace experiments conducted in 2007B and 2008A
revealed a significant effect of terrace development on the yieldFig. 6. Yield of NERICA-4 at treatments in 2007B and 2008A.

of NERICA-4 cultivated in an inclined field. The highest andlowest average rice yield of 1,568 and 777 Kg/ha wererecorded for 0.9 m terraces and the non-terraced controls(P<0.00003), respectively (Fig. 6). The above results imply
that terrace development apparently decreases the erosive
effect of slope gradient and improves rainfall catchment.
Moreover, 0.9 m terraces have significantly high yields thanthose of 1.5 m terraces (P<0.027) and 2.5 m terraces (P<0.0024).
This suggests that narrow sized terraces are more efficient in
rainfall catchment than the wide sized terraces (1.5 m and 2.5 m).
In 2009B, the average yield of NERICA-4 at the terrace
banked with filled sacks was 1713 Kg/ha, approximately 3times higher than that of the control (615 Kg/ha). Similarly,
the average yield of NERICA-4 between 2009B and 2010A atterraces banked with soil alone was 2572 Kg/ha (2.5mterraces), approximately 1.5 times higher than that of thecontrol (1685 Kg/ha). The results support to confirm theeffect of rainfall catchment on yield.
3.2. Effect of terrace development on the movement ofVolumetric Water Contents
In 2009A, moisture sensors failed and no data wascollected because of severe drought and the prolonged dry
spell. The total rainfall in the season was 290 mm which wasmuch lower than that of others (Table 1). Nevertheless, datacollected in 2009B showed that VWC was higher for the twotypes of terraces than in the non-terrace field (Fig. 5), which
proved the positive effect of both terrace types in improving
rainfall catchment. In addition, increases in VWC rates after
rainfall was 1.9, 9.0 and 9.1% for non-terraced fields (control),terrace banked with filled sacks, and terrace banded with only
soil, respectively (Table 2). The Average of increment rate ofVWC between the two terrace types is almost the same, but
four-times higher than that of the non-terraced fields. The
results above indicate that terracing can be an effective waterTable 2. Increasing rates (%) of soil volumetric water contents after
rainfall events.
Date of survey

1st Nov 19th Nov 4th Dec

5th Feb

7th Feb

Control

1.0

0.4

0.20

7.7

1.9

Scale Terrace

6.8

3.8

5.9

18.2

10.1

9.0

M ean

2.5m Terrace

7.5

8.5

8.5

12.9

8.1

9.1

Rainfall

40mm

22mm

25mm

47mm

70mm

N/A

Table 3. Number of existing rice plants in 3 m length in row.
No. ofsample

No. of riceplants existed

Control versus 2.5m Terrace
Control (Non-Terrace)
2.5m Terrace banked w ith soil
Mean difference t-test probability

6629.343.3
0.0003Control versus 5.0m Terrace
Control
2.5m Terrace banked w ith soil
Mean difference t-test probability

6629.340.3
0.00442.5m Terrace versus 5.0m Terrace
2.5m Terrace banked w ith soil
5.0m Terrace banked w ith soil
Mean difference t-test probability

6643.340.3
0.2415harvesting technology against a certain level of unexpected andinexplicable changes in the rainfall pattern. However,
because the use of terraces will prove futile in cases of severe
drought, they must be applied with other accompanied
technologies like irrigation that can bolster crop performance
during periods of severe drought or long dry-spell.
3.3 Terracing size and Number of existing rice plants
Our investigation revealed that the average number ofexisting rice plants in 3 m length in row are highly significant
between control and 2.5 m terrace banked with soil (P<0.0003),
control and 5 m terrace banked with soil (P<0.0044).
However there is no significant difference between the above
terraces (P<0.2415) (Table 3). The result suggests thatterrace development helped in decreasing missing plants whichwas caused by intensive rainfall.

4. Conclusions
Our result revealed that there are significant benefits interrace development in terms of rainfall catchment resulting inhigh soil VWC and high yield of rice. In addition, the resultsof rice yield showed that narrow sized terraces are more
effective than wide sized terraces in terms of rainfall catchment.
This result was considered as there is the movement of water inwide sized terraces when the field received intense deluges andwater cannot be distributed evenly within the terraces.
Narrow sized terraces have advantages of high yields andless labor requirements in comparison to wide sized terraces.

However it has disadvantages such as larger margin area,
where crops cannot be planted, created by banks than widesized terraces. Therefore it is important to conduct further
research to propose the best practice of terrace development interms of the size. In addition, other rice varieties such as earlyrice should be studied to know variety response to the water
harvesting in inclined fields.
In this paper, the authors tried to highlight the benefits ofterrace development on inclined rainfed fields in terms ofrainfall catchment. They would like to further suggest thatterrace development alone is not a perfect measure against
severe droughts as shown in the result of 2009A in which rice
was destroyed completely. To develop comprehensive
technologies to withstand severe drought, terrace development
should be applied with other water harvesting technologies
such as supplemental irrigation technology using consecutive
irrigation reservoir system as proposed by Kitanaka et al.
(2008).

Acknowledgement
We thank Dr. Godfrey Asea of National Crops Resources
Research Institute and Mr. Tsuboi Tatsushi of Japan
International Cooperation Agency in Uganda for their usefulsupport to the research and also thank the support staff who
managed the trials and collected the data with us in the field.
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