IJERD – International Journal of Environmental and Rural Development (2013) 4-1

Research article
erd

Alternative Cropping Systems for North-West Cambodia
I7de
STEPHANIE C. BELFIELD*nUniversity of New England, Armidale, Australiat
Email: smontgom@myune.edu.au
4.
Agricultural Systems Research Cambodia
7 Co. Ltd, Battambang, Cambodia
2

ROBERT J. MARTIN
J. FIONA SCOTTw
New South Wales Trade & Investment, Tamworth,Australia
Received 15 December 2012

orAccepted 27 March 2013
ds(*Corresponding Author)

Abstract A field research program commenced in north-west (NW) Cambodia in 2012 totest the feasibility of including a dry season crop for this upland area, increasing thecropping intensity from 2 to 3 crops per year. Dual purpose crop options that can be
harvested for fresh forage or silage in the event of crop failure due to drought will also beevaluated. Forest clearing after 1998 has been followed by the expansion of uplandcropping in NW Cambodia. Major threats to sustainable agricultural production in theregion are: (a) rapid soil degradation, soil fertility decline, loss of crop diversity; and (b)poverty and lack of income diversity for small-holder farmers. Access to improved
agricultural technologies could provide solutions to these problems. Current farmer
practice involves growing two crops per year, with an early wet season crop (March-June)and followed by a main wet season crop (July-October). Land is ploughed after the main
wet season crop or left fallow from November to February. Due to high rainfall in NW
Cambodia in September and October, there is significant residual water remaining in thesoil after the wet season that could be exploited by crops rather than weeds as it currently
is. The risk of growing dry season crops would be reduced if tillage was eliminated andsurface crop residues were retained to conserve soil water. Small-holder farmers in NW
Cambodia struggle to cover household expenses with crop income. Annual gross margins
from growing two crops of maize (USD 874/ha) are declining and farmers are turning tocassava (USD 1,066/ha) to increase income and reduce labour costs. Replacing early wet
season maize with peanut is more profitable (USD 1,447/ha); moreover adding dry seasonsunflower into the peanut-maize rotation to grow three crops per year could return a grossmargin of USD 1,888/ha.
Keywords upland cropping systems, land use efficiency, maize, sunflower, Cambodia

INTRODUCTION
North-West Cambodia has seen rapid expansion of rainfed upland cropping as a result of largescale land clearing since the end of the Khmer Rouge civil war in 1998. Unfortunately thisdevelopment has been associated with excessive cultivation and burning of crop residue which has
led to rapid soil fertility decline and soil erosion. The Australian Centre for InternationalAgricultural Research (ACIAR) has funded research since 2003 to address these problems and todevelop more sustainable upland cropping systems for NW Cambodia.
CROPPING SYSTEMS TRENDS
The rapid expansion of maize and cassava area, which began in 2006, has led to a loss of crop
diversity in the region (Fig. 1, Fig. 2). Maize yields are declining as soil fertility declines and thismay be one of the reasons why farmers have begun to increase the area of cassava at the expense ofⒸ ISERD209

IJERD – International Journal of Environmental and Rural Development (2013) 4-1maize (Fig. 2). The expansion of cassava could also be due to the need for less labour andopportunity for household members to earn off-farm income.

2005

2011

Fig. 1 Cropping trends in Battambang Province based on area of production(Data source: pers comm. Battambang Provincial Department of Agriculture)

Fig. 2 Trends in the area of red corn and cassava in Battambang Province
Data source: Battambang Provincial Department of Agriculture

CLIMATE AND SOIL
NW Cambodia has a monsoonal climate with a rainy season between May and October and a
distinct dry season between November and March (Fig. 3). The average annual rainfall atBattambang is 1,247 mm with 101mm, 391mm and 755 mm falling in the dry season (DS), early
wet season (EWS) and main wet season (MWS) respectively.

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Dry Season

Early Wet Season

Main Wet Season

Fig. 3 Average seasonal rainfall distribution at Battambang Town
(Data source: Battambang Office, Ministry of Water Resources and Meteorology)
The average temperature at Battambang is 28.0 oC. April is the warmest month with anaverage maximum temperature of 36.1 oC and December the coolest with an average minimum
temperature of 19.7 oC. Average relative humidity at Battambang is 80% rising to 86% in
September-October and falling to 72% in March.
The main soils where upland crops are grown in NW Cambodia are known locally as
Kampong Siem (Vertosol) and Labanseak (Ferrosol) (White et al., 1997). The Kampong Siem soils
are black self-mulching clays and the Labanseak are red friable clay-loams. Martin et al. (2005)
reported analyses for 25 ferrosols and 25 vertosols in crop fields in Ratanak Mondul District,Battambang Province. On average, the vertosols are higher in organic carbon and total nitrogen andhave higher pH than the ferrosols (Table 1). These clay and clay-loam soils have the capacity toretain significant quantities of plant-available water in dry periods between rainfall events.
Table 1 Organic carbon, total nitrogen and pH (0-15cm) of ferrosols and vertosols in Ratanak
Mondul District, Battambang
Soil
Organic carbon (%)
Ferosol
2.07 (1.36-3.81)
Vertosol
2.46 (1.45-4.50)
Data source: Martin et al. 2005

Total nitrogen (%)
0.176 (0.115-0.258)
0.181 (0.105-0.342)

pH (water)
5.5 (5.0-6.0)
6.5 (5.0-8.0)

ALTERNATIVE CROP OPTIONS
The main crops grown in the early wet season (March-June) include sesame, maize, mungbean andpeanut, while the principal crops grown in the main wet season (July-October) are maize andsoybean. Cassava is grown over a 12 month period.
There is potential for drought tolerant crops such as sunflower and sorghum to be grown
during the dry season (November - February) on residual soil moisture after harvest of the main
wet season maize crop, especially if the dry season crop could be sown at the end of October (Fig.
3). The success of the dry season crop is likely to be enhanced by no-till seeding into chopped
maize residue to better retain residual soil water from the main wet season rains.
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Inclusion of a dry season crop allows the potential for three crops to be grown during the year
compared to the current practice of growing one (cassava) or two crops per year: early wet season(March - June) and main wet season (July - October) (Fig. 4). The three crop option is only
possible if tillage is eliminated between crops to conserve soil moisture and enable timeliness ofoperations.

Fig. 4 Current upland crop calendar for NW Cambodia incorporating proposed dry season
sunflower (Data source: pers comm. B. Martin)
Technically both mungbean and soybean can be grown in the early and main wet seasons.
However, soybean is not drought tolerant and can fail in the early wet season. Mungbean crops
often fail in the main wet season because of fungal infection of the pods in the humid conditions.
Therefore it is recommended mungbean be planted only in the early wet season and soybean in themain wet season. Sesame is best grown in the early wet season to avoid attack from the sesame
webworm (Antigastra spp.)
Apart from the problems of soil degradation and lack of crop diversity, maize and cassava
fields in NW Cambodia are being invaded by tall grass weeds such as Sorghum halepense (Johnsongrass), Sorghum bicolor (wild sorghum) and Pennisetum polystachyon (mission grass). If left
uncontrolled after maize harvest, these grasses continue to grow throughout the dry season andconsume the residual soil moisture from the main wet season rains. This gives a strong indicationthat there is sufficient residual soil moisture to grow a dry season crop. Farmers in this region havealready experimented successfully with growing sunflower and sorghum in the dry season.
A challenge for introducing the dry season crop option is to successfully manage the maizecrop residues and weeds at harvest without losing valuable soil water. A maize stalk chopper and ano-till planter have been imported from the USA to enable small plot replicated on farm trials of
direct seeding of the dry season crop into the maize/weed residue. This will require chopping of themaize stalks and killing the weeds with a broad-spectrum herbicide (glyphosate) before direct
seeding the dry season crop. As part of research for a PhD and the afore mentioned ACIAR project,
trials with this system focusing on crop sequencing, cropping intensity and effects of maize residue
as a mulch under a no till farming system will commence in 2013 in collaboration with farmers.
Until the machinery is ready to use, trials will be hand planted following no till farming principles.
The important elements that a resilient crop sequence in NW Cambodia could include are:
1. A   ‘grass’   crop   such   as   maize   which   can   provide   sufficient residues to maintain groundcover mulch through the annual crop cycle;
2. A legume crop such as mungbean, peanut or soybean that can increase soil nitrogen
fertility through fixation of atmospheric nitrogen; and3. Other crop species such as sunflower or sesame to help to break disease, insect and weed
cycles.
ECONOMIC ANALYSISIn Battambang Province in 2011, maize and cassava were the dominant crops grown. Grossmargins have been calculated for cassava, maize, peanut and soybean based on interviews withfarmers in Samlout/Pailin in 2010/11 as part of the ACIAR project ASEM/2010/049 (Table 2). In
this case, crop gross margins are calculated (on a per hectare basis) as the gross income from thecrop less the variable costs incurred in achieving it, such as seed, fertilizer, in-crop weed controland harvesting costs. The potential gross margin for sunflower was calculated based on yield
estimates and prices from Thailand and the prices being aligned with those for soybean.
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Table 2 Gross margin sensitivity for cassava, maize, peanut, soybean and sunflower
Cassava fresh tuber.
USD32
USD77
USD115
USD154

Price (USD/t)
USD64
USD711
USD1,066
USD1,422

USD95
USD1,345
USD2,017
USD2,690

USD127
USD76
USD280
USD483

Price (USD/t)
USD159
USD171USD437
USD704

USD191
USD265
USD595
USD925

USD604
USD123
USD710USD1,297

Price (USD/t)
USD762
USD273
USD1,010
USD1,747

USD921USD423
USD1,310
USD2,197

Price (USD/t)
USD450
USD178
USD568
USD957

USD500
USD228
USD668
USD1,107

Price (USD/t)
USD450
USD126
USD453
USD780

USD 500
USD164
USD528
USD893

Yield (kg/ha)
20,00030,00040,000
Maize on cob
Yield (kg/ha)
3,000
4,500
7,000
Peanut in shell
Yield (kg/ha)
1,000
2,000
3,000
Soybean kernel
Yield (kg/ha)

USD4001,000USD128
2,000
USD4683,000
USD807
Dry season sunflower (low input, estimated)
Yield (kg/ha)
750
1,500
2,250
Data source: Anon. (2012)

USD400USD89
USD378
USD668

Table 3 Gross margin comparison for cassava, maize, peanut, soybean and sunflower
Crop sequence
Average Annual Gross Margin (USD/ha)
Maize-Maize
USD874
Cassava
USD1,066
Peanut-Maize
USD1,447
Sunflower-Maize-Soybean
USD1,458
Sunflower-Peanut-Maize
USD1,888
Data source: pers comm. K. Kynal 2010, University of Battambang students 2011

Table 3 shows the comparison of potential average annual gross margins (using the averageyields and prices) between the crop sequences under evaluation. At a first glance, farmers seem tobe justified in switching from maize-maize to cassava as the gross margin for cassava is higher
based on average yields and prices (Table 3). However, ACIAR research in Samlout/Pailin between
2008 and 2012 has shown that peanut can be a very profitable crop. A peanut-maize sequence could
give a much higher gross margin than maize-maize or cassava. The peanut-maize sequence is also a
better option to maintain soil fertility.
The addition of dry season sunflower to the peanut-maize cropping sequence would give an
estimated annual gross margin of USD1,888, which is more than double that for maize-maize andalmost double that for cassava. Another rotation option is sunflower-maize-soybean which is agood rotation option agronomically but might be less profitable than sunflower-peanut-maize(Table 3). However, this assumes relative crop prices remain the same. A disadvantage of thesunflower-maize-soybean option is that there is very little crop residue remaining after the soybean
crop and there would be less ground cover for the dry season crop.
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An important marketing consideration for sunflower, as with other crop species, is that thematurity of the NW Cambodian crop does not coincide with the harvest timing of the same crop
species in Thailand. Lopburi Province is the main sunflower production area in Thailand. The peakmonthly rainfall is September for Lopburi and October for Battambang so it is expected that theCambodian crop would be planted one month later than the bulk of the Thai crop. Battambang also
receives marginally more dry season rain (101 mm) than Lopburi (70 mm) meaning that dry season
sunflower production might be safer in NW Cambodia compared to Thailand.
The average yield of sunflower under rainfed conditions in Australia is around 1,700 kg/hawith a realistic range from 700 to 2,400 kg/ha (Serafin et al., 2011). It is expected that dry season
sunflower in Battambang Province could average up to 1,500 kg/ha. If the area of sunflower inBattambang Province expanded to 50,000 ha then the potential production would be at least 50,000
tonnes of sunflower seed per annum assuming a more conservative average yield of 1,000 kg/ha.
CONCLUSION
The current upland cropping system in north west Cambodia is facing many challenges including aloss in crop diversity, declining soil fertility, extensive soil erosion and continued deforestation.
Soil characterisation in this region is not well determined but soils are generally inherently fertile,
friable, well-structured soils, which if managed in a sustainable manner could greatly assist in
alleviating rural poverty. Research is ongoing into sustainable cropping systems for this region.
This research will provide the basic information required to improve soil management and wateruse  efficiency  in  upland  areas  of  NW  Cambodia.  It  will  also  develop  ‘response  cropping’  planting  guidelines to reduce the risk of crop failure due to drought and demonstrate to farmers alternative
cropping options on their land. The research will also identify the most suitable dual purpose cropsthat can be harvested for fresh forage or silage in the event of crop failure due to drought.
ACKNOWLEDGEMENTS
We would like to acknowledge the financial support of the Australian Centre for International
Agricultural Research (ACIAR).
REFERENCESAnon, 2012. Unpublished data from Australian Centre for International Agricultural Research project
ASEM/2010/049.
Martin, R.J., Belfield, S.C. and Holland, J.F. 2005. Farming systems research for crop diversification inCambodia and Australia. Report by on travel to Vietnam and Cambodia in July-August 2005. ACIAR.
(Project ASEM/2000/109)
Serafin, L., Byrne, R. and Jenkins, L. 2011. Summer crop production guide 2011. New South Wales
Department of Primary Industries.
White, P. F., Oberthur, T. and Pheav, S. 1997. Soil used for rice production in Cambodia. A manual for theirrecognition and management. International Rice Research Institute. P.O.Box 993, Manila, Philippines.

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