Intensification and diversification leading to increased productivity and profitability of rice-based lowland cropping systems in Lao PDR and Cambodia

This paper describes factors determining crop intensification and diversification in lowland rice-based cropping systems in Cambodia and Lao PDR, and discusses how mechanisation may assist increased productivity and profitability in the region. The work is based on two recently completed Australian Centre for International Agricultural Research projects on crop intensification and diversification in these systems in Cambodia and Lao PDR, and a newly commenced project in the same context on mechanisation and value-adding for diversification. Both water and labour availability are identified as key resource limitations for intensification and diversification of rice-based cropping systems. The policy implications of these and other factors leading to increased productivity and profitability are discussed

Floral morphology in rice grown under cold temperatures at booting and flowering and its effect on spikelet sterility

Booting and flowering in rice (Oryza sativa L.) are considered to be the two most sensitive stages to cold temperature stress. The controlled temperature glasshouse experiment compared a population of 120 genotypes from F6 Kyeema//Kyeema/NorinPL8 (KKN) when exposed to cold air temperature at the booting and flowering stages. The study aimed to examine the relationship between percentage of spikelet sterility (SS) and floral characteristics, namely the number of dehisced anthers (NoDA), anther dehiscence length (ADL), the number of pollen grains on stigma (PoS) and the anther length (AL) when subjected to cold temperature at the two development stages. Two sets of genotypes were sown 18 days apart and grown at 28/21°C day/night controlled temperature glasshouse, and were moved to the cold room (21/15oC day/night) at heading (set-1) and at early booting stage (set-2). A highly significant genotypic difference existed in percentage SS in both flowering (ranged from 49-100%) and early booting (4-99%) with flowering stage having higher average SS (88 vs 57%). A significant positive association existed between SS of flowering and booting (r=0.39**) with five genotypes performing consistently well. Highly significant negative correlations existed in both flowering and booting stage between SS and all the floral traits measured. Furthermore, multiple regression analysis indicated that 37% of the variation in SS was explained by the number of dehisced anther, anther dehiscence length and anther length when exposed to cold at flowering stage, while at booting stage the number of dehisced anther and anther length alone explained 58% of the variation in SS. The importance of the number of dehisced anther in explaining variation in SS has been highlighted and plays a significant role in cold tolerance

Semi-automated, non-weighing, pot-in-bucket (PIB), water management in pot plant culture

Constant water tables (CWT) in pots have been used in the determination of plant water-use. While the CWT systems eliminate the labour required in watering-to-weight systems, they may be overly wet with the constant water table within the pot itself. A valve in our Pot-In-Bucket (PIB) system maintains the water table at a nominated constant height above, within or below the contents of each test pot. In the latter configuration, the CWT supplies water to an upper ANOVApot® through a capillary tape draped over an upturned pot within the bucket which encloses the valve and supports the upper ANOVApot®. This valve is connected to a remotely located 5L container of water via a medical infusion set. Water-use by a plant/s growing in the ANOVApot® is monitored as changes in water level in the calibrated 5L container. Real time (2-20 minute delay) variation in rate of water-use from plants can be observed (as drips (0.066mL) per second) in the sight glass of the infusion set. Having groups of containers located remotely from the pots they supply, greatly facilitates the ease and speed of the refilling operation and drip rate measurements. Changes in pot weight provide a measure of whole plant biomass and when coupled with water-use enables the non-destructive measurement of water-use efficiency during the crop’s lifecycle. This system has worked well in water-use experiments in wheat and rice

Factors Determining Genotypic Variation in the Speed of Rice Germination

Rapid germination is important for both direct seeded rice in the field and for the production of germinated brown rice for healthy food. This study aims to evaluate genotypic differences in germination speed and identify characteristics that determine germination speed. Seven experiments were conducted to determine (i) the impact of dehulling on water absorption and germination, (ii) variety consistency in germination speed across crops grown in three years, and (iii) the effect of grain size. Germination speed in both paddy rice and dehulled brown rice was significantly correlated with grain moisture content at early stages of soaking, however significant interaction of genotype and grain type (paddy and brown rice) existed and varieties differed in their response to dehulling. Germination speed of grain from crops exposed to water deficit in the field was slightly slower than those with higher water supply. Sherpa/IRAT109 genotypes with smaller grain size tended to germinate faster than larger grain, however no significant effect of grain size existed among diversity set varieties. It was concluded that genotype ranking in germination speed was consistent across years and water availability conditions, and that barriers to water absorption in hull and pericarp were important determinants of germination speed. The existence of genotypic variation in germination speed has management implications for both field crop establishment and paddy germination in food processing

Research strategies for mechanised production of rice in transition from subsistence to commercial agriculture: a case study from Khammouan in Lao PDR

Mechanised rice production has started to take place in response to rural labour shortage and increased labour cost in Khammouan province in central Laos where subsistence rice production is being replaced with commercial agriculture. This paper summarizes the results of recent findings of four mechanised items, combine harvester, seed drill, transplanter, and artificial grain dryer, and discusses research strategies for advancement of the mechanised rice production system. Combine and seed drill were considered to have good potential for reduction in production cost and hence the likelihood of farmer adoption. Synergistic effects of these four and other items are noted; for example, the adoption of combine harvesting service is associated with farmer’s accessibility to drying facilities. Artificially dried grain has been shown to decrease broken rice component during the milling process, resulting in higher grain quality, and hence increased marketability. The proposed research strategies focus on the production of rice with reduced cost and increased grain quality for increased farmer adoption of contracting services available for mechanised rice production. The strategies include promotion of large size paddy fields to allow efficient use of machinery and reduced service fees. Other strategies which are discussed include identification of suitable rice varieties and other technologies that maximize in field machinery efficiency. The requirements of actors in the rice value chain working together for mechanised rice production are emphasised

Low canopy temperature and high stomatal conductance contribute to high grain yield of contrasting japonica rice under aerobic conditions

Water limitation is a major concern in rice production. It has been suggested that with adapted genotypes, aerobic rice production offers the maintenance of grain yield while saving water. However, there has been limited exploration of japonica germplasm adapted for high-yield aerobic environments. Therefore, three aerobic field experiments with different levels of relatively high-water availability were conducted across two seasons to explore genetic variation in grain yield and physiological traits that contributed to high yield. In the first season, a japonica rice diversity set was explored under well-watered (WW20) conditions. While in the second season, a well-watered (WW21) experiment and an intermittent water deficit (IWD21) experiment were conducted to examine the performance of a subset of 38 genotypes selected for low (mean of −6.01°C) and high (mean of −8.22°C) canopy temperature depression (CTD). In WW20, CTD explained 19% of the variation in grain yield which was similar to the variation explained by plant height, lodging, and leaf death response to heat. In WW21, a relatively high average grain yield (9.09 t ha−1) was achieved, while a 31% reduction was achieved in IWD21. Compared with the low CTD group, the high CTD group had 21% and 28% higher stomatal conductance, 32% and 66% higher photosynthetic rate, and 17% and 29% higher grain yield in the WW21 and IWD21, respectively. This work demonstrated the advantage of higher stomatal conductance and cooler canopy temperature which resulted in higher photosynthetic rate and higher grain yield. Two promising genotypes with high grain yield, cooler canopy temperature, and high stomatal conductance were identified as donor genotypes for use by the rice breeding program when aerobic rice production is a target. Field screening for cooler canopies within a breeding program with high-throughput phenotyping tools would be of value for genotype selection for aerobic adaption

Traits of importance for aerobic rice

Irrigation water is limited and costly and for the Australian Rice Industry based in the Riverina, this has become a major limitation to production. Aerobic production (well-watered, non-flooded) has been proposed to improve water productivity. However, historically in Australia, varieties have been developed for continuously flooded growing conditions and as such the appropriateness of the germplasm to aerobic adaptation needs to be explored. Deeper rooting is one trait that is believed to be associated with improved aerobic performance by ensuring plants are less susceptible to fluctuations in water availability in the top 20 cm of the soil profile. Two field experiments evaluating 20 genotypes were conducted to examine genetic variation and relationships between root traits and grain yield. Two methods for root trait observations were conducted. A basket method was utilised for 15 genotypes in one experiment, while soil cores at maturity were collected from all plots in both experiments. Highly significant (p0.90). Grain yield had a highly significant genetic correlation (rg= 0.56**) with the percentage of roots below 20 cm at maturity which demonstrated the advantage of a deeper root system in aerobic conditions. Several lines, most notably Australian variety Sherpa, demonstrated high yields in aerobic conditions but only moderate expression of deep roots. These results suggest the incorporation of deep rooting characteristics into high yield potential backgrounds (e.g. Sherpa) has the potential to close the yield gap between aerobic and traditional flooded production