SUMMARYExperiments were conducted across 2 years to determine the effect of harvesting methods – combine harvester and hand harvesting – and harvest time during ripening on milling quality of long grain rice grown in the rainfed lowland ecosystem in Cambodia. Head rice yield (HRY) was highest when rice was harvested 25 days after flowering and decreased with delay in harvesting at 35 and 45 days after flowering. This was accompanied by a general decline in grain moisture content at harvest, although it was still high at 24–25% at 35 days after flowering. The decline in HRY was associated with increases in fissured grain percentage observed immediately after harvest. Hand harvesting produced 2–6% higher HRY than combine harvesting. Fissured grain in hand harvested crops was lower in year 1, but was similar to combine harvested crops in year 2. Both hand and combine harvested crops were sun-dried but rough rice harvested by combine was dried on plastic sheet and this may have contributed to reduction in HRY. Maximum HRY percentage was only about 44% and the factors contributing to this low HRY were discussed. Harvesting time and methods had no significant effect on grain yield, but the field grain loss during the harvesting operation was 2–5% higher in combine than hand harvesting.

Combine has been well adopted by smallholders in lowlands of Cambodia and is contributing to the development of mechanized rice production for commercial purposes. Broken rice is a major issue for the commercial rice product, and fissured grain at harvest leads to broken rice and lowers head rice yield (HRY) during milling. Factors that determine grain fissures and broken rice were obtained from three studies: an on-farm study of fissured grain, a research station experiment of fissured grain and broken rice harvested at different ripening stages and a mill study of fissured and broken rice during drying and milling processes in Cambodia. There was significant variation in fissured rice percentage among 20 farms sampled, and the fissured grain was negatively correlated with grain moisture content at harvest. Time of harvesting was crucial, as delay in harvesting after 25 days after flowering (DAF) often resulted in lower grain moisture content and higher fissured grain, which subsequently reduced HRY. However, the optimum time of harvesting varied across four seasons for crops harvested manually or by combine. In some years, crops harvested at 35 DAF had rather low per cent fissured grain with subsequently high HRY, this may have been associated with slightly lower temperatures. The mill study showed that fissured grain developed during the drying, storage and milling processes. It is concluded that while grain moisture content at the time of harvest may be used as an indication of subsequent HRY, the latter was more strongly related to fissured grain at harvest.

In this and the next five chapters the focus is on the commercialisation of rice farming in the Central Plain of Cambodia. Particularly since 2010, rice has come to be seen as more than merely a subsistence crop or a staple for domestic consumption but as “white gold”—a commodity with major commercial, including export potential. This chapter sets the scene for the in-depth studies on the commercialisation of rice farming in Cambodia by describing the rice-growing environment in Cambodia as a whole, outlining the history of rice production in Cambodia, examining the role of the rice sector in the rapid agricultural and economic growth in Cambodia since 1993, highlighting the changes at the farm level that have underpinned this agricultural growth, and providing a profile of Takeo Province within this larger context. Cambodia has a long history and comparative advantage in rice production. With relative political stability and access to improved varieties and other inputs, farmers have been able to increase the area cultivated and especially per-hectare yields so that total production has grown at over 5% since 1990. From being a rice-deficit country in the 1980s, the country has achieved self-sufficiency and, since 2010, become a serious exporter of paddy and milled rice. Rice farmers in Takeo Province have long made an important contribution to Cambodia’s rice production and currently contribute 8% of wet season output and 19% of dry season output, as well as a major share of exports.

This chapter is based on a study to explore the key constraints to ricebased farming systems in the rainfed lowlands of Cambodia and the role of different sources of irrigation in alleviating some of those constraints (Chea 2015). The research was carried out in lowland districts in Takeo and Kampong Speu Provinces in the southern part of the Tonle Sap Basin, representing a major lowland rice-growing region with high population density, small farm sizes, and severe production constraints (Fig. 13.1). Three villages were selected with similar biophysical and socioeconomic environments but different degrees of access to irrigation:

Rainfed lowlands account for nearly 90% of the total rice area in Cambodia. Annual rice production from the rainfed lowlands is over 7 million tonnes accounting for 77% of total rice production.However, the majority of rainfed lowland farm households are resource-poor, owning less than a hectare of paddy land, and, given the monsoonal (wet-dry) climate, grow only a single low-yielding rice crop per year in the wet season (WS), primarily for subsistence. This lowland rice farming system is subject to various pressures from unreliable rainfall, poor soil fertility, insect and weed pests, the use of traditional varieties and cropping practices, restricted access to irrigation, and limited farm resources. Moreover, there are few options for earning cash income, given the reliance on subsistence rice cultivation in the WS and the inability to use land and labour productively in the dry season (DS).The research reported in this thesis aimed to explore the potential for agricultural development and poverty reduction in the rainfed lowlands of Cambodia, with particular emphasis on the role of irrigation. First, the thesis sought to evaluate the situation, constraints, and management of farms in rainfed lowland villages in southern Cambodia. Next, it compared the options available to farm managers and village communities in similar biophysical and socioeconomic environments but with different degrees of access to irrigation. Finally, it identified the potential development pathways and adaptive responses of farm managers in the rainfed lowland environment.The research was carried out in rainfed lowland districts in Takeo and Kampong Speu Provinces, representing a typical lowland rice-growing region that was densely-populated and with low percapita ownership of paddy land. A comparative case-study design was used with multiple units of analysis. Three villages were selected that experienced similar biophysical and socioeconomic environments but had different degrees of access to irrigation, with Trapeang Run depending on small houseyard ponds, Snao using tubewells to extract groundwater, and Ta Daeng Thmei benefiting from gravity-fed irrigation from a medium-size reservoir. Each village was considered as an individual case, with cross-case comparison used to develop generalisations about the research objectives.A range of research methods were employed between 2010 and 2013 for data collection, including reconnaissance visits, household surveys, discussions with village heads, key informant interviews, analysis of market trends, farm walks and direct observation, use of village data manuals and documents, surveys of pond-water and groundwater, analysis of rainfall data, soil surveys, and field crop experiments. Analytical methods applied to the analysis of household survey data and other data comprised conventional descriptive statistics, multivariate statistical techniques, and iii conventional farm management economics, adapted to the perspectives of semi-commercial farm households.Trapeang Run was typical of ra...