Triple Rice Research Articles

Questioning triple rice intensification on the Vietnamese mekong delta floodplains: An environmental and economic analysis of current land-use trends and alternatives

Large areas of the Vietnamese Mekong Delta floodplains (VMDF) are protected by high dikes to facilitate three rice crops per year. While this has increased rice production, there is evidence that triple rice systems have negative long-term effects, both environmental and economic. Double rice cropping, or other alternatives, may be more advantageous. We analyzed the costs and benefits of intensive rice systems over time and compared these with alternatives farming systems, based on data collected via field surveys and interviews with farmers in two provinces in the VMDF. Results show that farmers in areas with dikes high enough for triple rice production incurred rising production costs over time. Production costs were 58%–91% higher in high-dike, triple crop areas, than in low-dike double rice crop areas. Higher production costs are mainly the result of increased fertilizer and pesticide use. Profitability of triple rice farming systems was initially 57% more compared to double crop systems. After about 15 years, however, triple rice farmers earned only 6% more than double crop counterparts. Our results indicate that alternative farming systems, such as rice combined with vegetables, fisheries or other flood-based livelihood, could offer greater benefits than intensive rice monocultures. Importantly, these higher benefits can be obtained without the environmental costs and impact currently endured across the delta with triple rice cultivation in high dikes.

Đánh giá tính tổn thương đối với đất nông nghiệp trong điều kiện biến đổi khí hậu cho các tỉnh ven biển Đông Đồng bằng sông Cửu Long

The study aimed to evaluate the factors and agricultural zones suffered by climate change in 8 land use type including triple rice cropping, double rice cropping, intensive shrimp, rice-shrimp rotation, rice-cash crop rotation, fruit orchard, sugar cane, and intensive cash crop. The data was collected via 192 farmer and expert interviews. The data was analyzed and assessed by multi-critical evaluation and geographic information system. The results showed that saline and flood were the most influencial factors to triple rice cropping, double rice cropping, intensive shrimp, rice-shrimp rotation, rice-cash crop rotation, fruit orchard, sugar cane, and intensive cash crop. The flooding factor was the most influencial factor to the sugar cane and fruit orchard. This study determined 5 vulnerability levels to agricultural production systems including very low, low, medium, high, and very high. The vulnerability areas at medium, high and very high levels tended to increase while the vulnerability areas at very low and low levels showed a decreasing trend in 2016, 2030, and 2050.

Improving Resource Use Efficiency of Cereal Based Cropping Systems with Integration of Best Management with Conservation Agriculture Under Changing Agricultural Scenarios in Cauvery Delta of Tamil Nadu

Cropping systems in Cauvery Delta Zone of Tamil Nadu is intensive rice based with double or triple rice crops in a year. The rice system in the region is threatened by yield stagnation, scarcity of water and labour, increased costs of cultivation, and resource degradation. During 2009-2012, we evaluated four scenarios involving a range of best management practices (BMPs) with and without conservation agriculture (CA) components for improving the system productivity and economic returns of rice-based system. Four scenarios were (i) current farmers’ practice (S1), (ii) BMPs with conventional tillage (S2), (iii) BMPs with conservation agricultural technologies (S3), and (iv) BMPs with conservation agricultural technologies along with crop diversification (S4). The key parameters tested were crop yields, system productivity, labour and energy use efficiency, and economics. Results indicated that compared to S1, the BMPs in S2 improved system crop productivity (22–57%), and net economic returns (67–166%) with reduced cultivation cost (10-16%), and total system energy use (4.4-8%), and higher labour productivity (18-59%). Compared to farmers practices (S1), BMPs with CA practices such as zero/reduced tillage, direct seeding of rice in dry season and mechanical transplanting of rice in wet season (S3) had lower labor (14-25%) and energy (20-37%) usages with higher economic returns (25-73%). Crop diversification with maize in place of dry season rice in S4 though saved in labor input, crop productivity and economic returns were also lower. This study concluded that there is potential of improving productivity and economic returns of rice based cropping systems with BMPs and CA in Cauvery Delta Zone of Tamil Nadu. However, more medium to long-term adaptive system research is needed to identify compatible alternative crops/management practices in rice based systems to diversify the food production and increase the system productivity while conserving the natural resources.

Floodwater ammonium, nitrogen use efficiency and rice yields with fertilizer deep placement and alternate wetting and drying under triple rice cropping systems

Fertilizer management should consider optimum time, rates and methods of application to increase use efficiency and crop yield. We conducted field experiments at Bangladesh Agricultural University, Bangladesh, to investigate the effects of deep placement of urea briquettes (UB) and NPK briquettes (NPK) compared to broadcast prilled urea (PU) at different N rates on dynamics of floodwater NH4 +-N, ammonia (NH3) volatilization, rice yield and nitrogen use efficiency (NUE) during four consecutive rice-growing seasons in 2012–2013. The floodwater NH4 +-N and NH3 volatilization in broadcast PU increased with N rates, while in deep-placed treatments irrespective of N rates it was similar to the control. Across seasons and water regime, UB or NPK significantly (P < 0.05) increased grain yield and nitrogen recovery compared to broadcast PU. During the Boro season (across water regime), UB78 and NPK78 increased grain yield by 40 and 29 %, respectively, compared to broadcast PU78, while N recovery increased from 35 % of PU to 63–67 % in deep placement. Deep placement of UB52 or NPK52 during Aus–Aman and UB78 or NPK78 during Boro can be one of the best N management options for increasing NUE and crop yield. Alternate wetting and drying irrigation, though, had no significant effect on grain yield or on NUE. Its adoption could save irrigation water without any yield reduction during the Boro season. However, more studies across different soils, climate and management practices are needed for further understanding the interactive effects of fertilizer and water management on yield, NUE and soil fertility.

Tác động của mặn và ngập theo kịch bản biến đổi khí hậu đến tiềm năng thích nghi đất đai vùng ven biển Đồng bằng sông Cửu Long

Agriculture is an important sector in the Vietnamese Mekong Delta (VMD), a major agricultural zone in Vietnam. Besides, the VMD has been identified as being particularly susceptible to the impacts of climatic variability. Land use systems in the coastal zones of the VMD have changed to improve local farmers’ income and to adapt to changes of socio-economic settings and natural conditions, especially in the climate change context. The data on natural conditions, current land use types, land use planning and scenarios of climate change (sea level rise and salinization) in VMD were collected. In this study, physical land suitability evaluation was implemented for 10 major land use types in the coastal provinces of the VMD (including: triple rice cropping, double rice cropping, single rice cropping, rice - cash crop rotation, rice – shrimp rotation, intensive shrimp, shrimp/mangrove, intensive sugarcane, intensive cash crop and fruit orchard) by using the land evaluation approach (FAO, 1976) in different scenarios. The results showed that there were 09 land suitability units of 10 major land use types in both the present and future climate change scenarios (2030 and 2050), and identified the dispute areas between of freshwater and salinity water affected to land use change in Kien Giang, Ca Mau, Bac Lieu, Soc Trang, Tra Vinh and Ben Tre. This study provided a good reference in orientation of agricultural land use planning and support adaptation and mitigation strategies for climate change in the future.

Increasing profitability and water use efficiency of triple rice crop production in the Mekong Delta, Vietnam

SUMMARYRice production in the Mekong Delta, Vietnam is threatened by future water scarcity caused by changing rainfall patterns and increasing irrigation costs. To improve resilience of the triple rice farming system to future climate-related stresses, profitability needs to be increased through water use efficiency, fertilizer management and planting methods.During four cropping seasons in 2011–13, alternate wetting and drying (AWD) irrigation was applied in the triple rice production area within An Giang Province, Vietnam. An issue with the application of AWD is the prevalence of acid sulphate soils in the Mekong Delta. Three types of irrigation management were tested; continuously flooded (CF) where the water in the paddy was maintained at 5 cm; AWD where the water level was allowed to fall to 15 cm below the ground surface, at which point the field was irrigated until the water level was at 1 cm above the ground surface (designated −15 cm); AWD where the water level was allowed to fall to 30 cm below the ground surface before irrigation until the water level was at 1 cm above the ground surface (designated −30 cm). Two further experiments were also undertaken which examined the planting method (transplant v. direct sowing) and phosphorus rate on rice yield. There was no effect on yield caused by P fertilizer rate and irrigation management in any year, and there was no significant effect on soil pH or salinity caused by irrigation management. Overall net profitability was greatest for the AWD treatments because of the reduction in pumping and labour costs in the dry season. Transplanted rice improved yields, but the labour cost reduced overall profitability. The study shows that AWD (−15 cm) can be safely applied in acid sulphate soil areas within the triple rice areas of An Giang Mekong Delta and saved at least 0·27 of total irrigated water quantity used during three of the six cropping seasons. The increased profitability of the AWD rice production system will help to improve the resilience of triple rice cropping systems to future water scarcity.

Rice Straw Management by Farmers in a Triple Rice Production System in the Mekong Delta, Viet Nam

Rice Straw Management by Farmers in a Triple Rice Production System in the Mekong Delta, Viet Nam

Greenhouse gas emissions from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta

The Mekong Delta produces 21 Mt of rough rice (Oryza sativa L.) and an estimated 24 Mt of straw (dry weight) annually. Approximately one fourth of the straw is burned on the field, which is a common practice in intensive rice cultivation systems in this region because there is limited time to prepare the field for the next crop. The spread of intensive rice production in the Delta may increase the total biomass of burning crop residues, significantly impacting greenhouse gas (GHG) emissions in Vietnam. In this study, GHG emissions from the major uses of straw (burning and mushroom beds) were monitored in a triple rice cropping system located in the central Mekong Delta. Between September 2011 and November 2012, both wind tunnel and closed chamber methods were used to measure the emissions of major GHGs from straw-burning and straw-mushroom cultivation systems, respectively. The global warming potential (GWP) was then determined. Methane (CH4) and non-methane volatile organic carbon emissions (NMVOC) increased with lower modified combustion efficiency [MCE: emissions ratio of Carbon composing carbon dioxide (CO2-C) and carbon monooxide (CO-C) (CO2-C/(CO-C + CO2-C))]. Furthermore, higher moisture straw stacks generated lower nitrous oxide (N2O) emissions. Small straw stacks (5 or 10 kg dry straw) with higher moisture content emitted more carbon monoxide (CO), CH4 and NMVOC. These results suggest that factors that increase the straw moisture content, such as rainfall, can cause smoldering combustion in small straw stacks or when straw is scattered on the ground, thereby inhibiting N2O emissions but enhancing CO, CH4 and NMVOC. The measured N2O emissions contributed negligible amounts to the GWP compared with measured CO and CH4, which are relatively intense GHG emissions; this was likely a result of the slow and inefficient burning that was observed from the smaller straw stacks with higher moisture content. In this study, rice straw burning threatened to generate more GHGs than straw-mushroom (Volvariella volvacea (Bul. ex Fr.) Singer) cultivation under the studied agroecosystems.

Mapping the irrigated rice cropping patterns of the Mekong delta, Vietnam, through hyper-temporal SPOT NDVI image analysis

Successful identification and mapping of different cropping patterns under cloudy conditions of a specific crop through remote sensing provides important baseline information for planning and monitoring. In Vietnam, this information is either missing or unavailable; several ongoing projects studying options with radar to avoid earth observation problems caused by the prevailing cloudy conditions have to date produced only partial successes. In this research, optical hyper-temporal Satellite Pour l'Observation de la Terre (SPOT) VEGETATION (SPOT VGT) data (1998–2008) were used to describe and map variability in irrigated rice cropping patterns of the Mekong delta. Divergence statistics were used to evaluate signature separabilities of normalized difference vegetation index (NDVI) classes generated from the iterative self-organizing data analysis technique algorithm (ISODATA) classification of 10-day SPOT NDVI image series. Based on this evaluation, a map with 77 classes was selected. Out of these 77 mapped classes, 26 classes with prior knowledge that they represent rice were selected to design the sampling scheme for fieldwork and for crop calendar characterization. Using the collected information of 112 farmers’ fields belonging to the 26 selected classes, the map produced provides highly accurate information on rice cropping patterns (94% overall accuracy, 0.93 Kappa coefficient). We found that the spatial distributions of the triple and the double rice cropping systems are highly related to the flooding regime from the Hau and Tien rivers. Areas that are highly vulnerable to flooding in the upper part and those that are saline in the north-western part of the delta mostly have a double rice cropping system, whilst areas in the central and the south-eastern parts mostly have a triple rice cropping system. In turn, the duration of flooding is highly correlated with the decision by farmers to cultivate shorter or longer duration rice varieties. The overall spatial variability mostly coincides with administrative units, indicating that crop pattern choices and water control measures are locally synchronized. Water supply risks, soil acidity and salinity constraints and the anticipated highly fluctuating rice market prices all strongly influence specific farmers’ choices of rice varieties. These choices vary considerably annually, and therefore grown rice varieties are difficult to map. Our study demonstrates the high potential of optical hyper-temporal images, taken on a daily basis, to differentiate and map a high variety of irrigated rice cropping patterns and crop calendars at a high level of accuracy in spite of cloudy conditions.

Classification of rice cropping systems by empirical mode decomposition and linear mixture model for time-series MODIS 250 m NDVI data in the Mekong Delta, Vietnam

Estimating the area of rice planting is vital for production prediction. This study utilizes time-series MODIS NDVI data from 2002 to 2007 to discriminate rice cropping systems in the Mekong Delta (MD), Vietnam. Data are processed using Empirical Mode Decomposition (EMD) and the Linear Mixture Model (LMM). Various spatial and non-spatial data are also collected for accuracy validation. The results indicate that EMD acts as a well-fitted filter for noise reduction of the time-series NDVI data. The classification results derived from the LMM for 2002 showed an overall classification accuracy of 71.6% and a Kappa coefficient of 0.6. The provincial level area estimates were strongly correlated with the rice statistics. An examination of the change in cropping patterns between 2002 and 2007 showed that 29.0% of the triple irrigated-rice cropping systems had been changed to double irrigated-rice cropping systems and that 12.0% and 9.0% of the double irrigated and rainfed-rice cropping systems, respectively, had been changed to triple rice cropping systems. These changes were verified by visual comparisons with Landsat images.

Variations in water resources in the Vietnamese Mekong Delta in response to climate change and their impacts on rice production

A numerical hydraulic model was developed and used to investigate the spread of salinity intrusion and the propagation of flooding in the Vietnamese Mekong Delta under two proposed scenarios: “baseline” (2000s) and “future” (2090s). The baseline scenario was based on observed hydrological and salinity intrusion data from 1998 to 2006. The changes in upstream flow discharge in the future scenario (increased for most of the year) were derived from previous research results obtained using the Japan Meteorological Agency atmospheric general circulation model output for the IPCC SRES A1B scenario. The sea level rise in the A1B scenario (a projected 53-cm increase) was also included in the future scenario. The resulting salinity intrusion and flood water levels were then used to roughly estimate possible rice cropping durations. We found that large adverse changes in duration of rice cultivation in the future scenario were caused mainly by floods with greater peaks, larger areal extents, and longer durations. The area potentially suitable for growing triple rice crops decreased from 31% of the total delta area currently to 5%, whereas that potentially suitable for a single rice crop increased from 21% currently to 62%. Using GIS techniques, we divided the delta into three areas with different levels of rice vulnerability levels. Areas of high and medium vulnerability covered approximately 31 and 36% of the total delta area, respectively.

Analysis of rapid expansion of inland aquaculture and triple rice-cropping areas in a coastal area of the Vietnamese Mekong Delta using MODIS time-series imagery

We applied a remote-sensing method using MODIS time-series imagery to detect the expansion of intensive farming systems (shrimp farming and triple rice cropping) in the Soc Trang and Bac Lieu provinces of the Vietnamese Mekong Delta (VMD). Field surveys for interpreting the estimates derived from the remote-sensing analyses were conducted in June and September 2007. From 2000 to 2006, there has been rapid expansion of inland aquaculture, especially shrimp farming, in the western part of the Bac Lieu province and the coastal regions of both the Bac Lieu and Soc Trang provinces. The triple rice-cropped area expanded concentrically from specific small locations in the Bac Lieu province from 2001 to 2006. The triple rice-cropped areas in Soc Trang province also expanded concentrically from 2001 to 2003, but some of these new triple rice-cropped areas returned to double rice cropping after 2004. Interviews with farmers and ancillary hydrological monitoring data suggested that changes in the water environment and transmission of information about new farming systems are closely connected with the annual expansion of triple rice-cropped areas in both provinces. The availability of salt-free irrigation water in the dry season may have led some pioneering farmers to attempt full-scale dry-season cropping. Furthermore, successful dry-season harvests and recent increases in the price of rice might have encouraged neighboring farmers to follow suit. Based on MODIS time-series imagery with field interviews at land-use change hotspots, the spatial structure of coastal farming systems and their recent changes were revealed from a macroscopic view point.

Detection of Yearly Change in Farming Systems in the Vietnamese Mekong Delta from MODIS Time-Series Imagery

This paper briefly introduces an integrated remote-sensing methodology based on MODIS time-series imagery for detecting spatiotemporal changes in Vietnamese Mekong Delta (VMD) farming systems. The integrated methodology consists of six parts, and uses a wavelet-based filter to smooth MODIS-derived time-series indexes (EVI, LSWI, and DVEL) from 2000 to 2008. Through a proposed decision tree using the smoothed indexes, we classified several farming systems, viz., triple rice cropping, two types of double rice cropping, shrimp-rice farming (rotational cropping), and inland aquaculture (monoculture). The MODIS-derived estimate of the total rice-planted area, shrimp-rice farming area, and inland aquaculture area agreed well with statistical data at the province level (R2 ≥ 0.96). However, in some provinces, the estimate has a large margin of error, probably because of the mixed-pixel effect due to the moderate spatial resolution of MODIS (250 m). According to the estimated spatial pattern of the farming systems in the whole VMD, inland aquaculture and shrimp-rice farming areas are distributed mostly in the coastal provinces. The areas of the farming systems steadily expanded until 2007, and double rice cropping systems in both upper and coastal regions were replaced by triple rice cropping because of infrastructure improvements. The proportion of the triple rice cropping area peaked in 2005 and then declined steadily over the next 2 years. We discuss the advantage of the proposed methodology for detecting the spatiotemporal changes of land use patterns, especially of farming systems in a regional area.

Sensitivity of Salinity Intrusion to Sea Level Rise and River Flow Change in Vietnamese Mekong Delta-Impacts on Availability of Irrigation Water for Rice Cropping

The combined impact of sea level rise and reduction of the Mekong River flow in the dry season on salinity intrusion and rice cropping in the Vietnamese Mekong Delta was assessed in this study. The MIKE11 model was used to simulate flow and salinity intrusion from December to June for the medium-term (mid-2030s) and long-term (mid-2090s) scenarios using data derived from the SRES B2 climate change projection. The sea level rise values for two scenarios were +20 cm and +45 cm, while the rates of change for the Mekong River flow were -15% and -29%, respectively. The results obtained for the mid-2030s and mid-2090s scenarios show that the 2.5 g/L saline front is likely to shift upstream by 10 km and 20 km in the main river channels, and up to 20 km and 35 km in the paddy field, respectively. The simulated salinity intrusion results were then used to compute durations of available water for irrigating rice cropping. The results indicate that area where triple rice crops are possible, will be reduced by approximately 71,000 and 72,000 ha, while single crop areas will be increased by approximately 38,000 and 179,000 ha for the mid-2030s and mid-2090s scenarios, respectively. Using GIS techniques the delta was divided into three areas reflecting different rice crop vulnerability levels; areas of high and medium vulnerability measured approximately 200,000 ha and 400,000 ha, respectively.

Differences in the Changes of Ferrous Iron Content and pH Values in Soils under Single, Double and Triple Rice Cultivation Systems in Tropical Area

Differences in the Changes of Ferrous Iron Content and pH Values in Soils under Single, Double and Triple Rice Cultivation Systems in Tropical Area

Methane emission from rice cultivation: Geographic and seasonal distribution of cultivated areas and emissions

We present high‐resolution global data bases on the geographic and seasonal distribution of rice cultivation and associated methane emission. The data bases were developed by integrating extensive and eclectic information on the cultivation of rice in all 103 rice‐producing countries of the world. The geographic distribution of rice‐growing locations was developed by combining a 1° resolution land‐use data base identifying rice‐farming regimes, a 1° resolution data base of countries of the world, and country statistics on areas of annual rice harvest available from the U. N. Food and Agriculture Organization. The seasonal distribution of cultivated rice areas was derived via the integration of the data base on rice‐growing locations with information on cultivation activities and rice cropping practices for each rice‐producing country of the world; this information included seasonal rice‐cropping calendars for individual countries and statistics or estimates of the seasonal distribution of annual harvest areas in each crop cycle. Since the causes of the variability in methane fluxes from flooded rice fields have yet to be quantified, we did not attempt a new estimate of the role of rice cultivation in the global emission of methane. We evaluate, instead, the temporal and spatial distribution of emissions from a hypothetical annual source of 100 Tg methane. In 1984, 1475 × 109m2 of rice was harvested in 103 countries. Although rice cultivation extends from about 50°N to 50°S, 48% of the harvest area is confined to a narrow subtropical zone from 30°N to 20°N, while another 35% is harvested in the 10° zones directly to the north and south. Globally, about 60% of the harvested rice area is managed under a triple rice crop system, ∼15% is double cropped, and 25% is harvested from fields planted for rice once a year. In China and India, which together account for 52% of the world's harvest area, rice is harvested predominantly under a triple‐crop system. These patterns suggest that much of the potential for multiple rice cropping is currently exploited. In this analysis, methane emission is proportional to the area and duration of each harvest so that the seasonal, zonal and country patterns of annual methane emission mimic the distribution of rice‐harvest areas. Although rice is grown throughout the year, the close coupling of rice cultivation with climate results in the concentration of about 55% of the annual methane emission into four months from July through October and almost half the total emission in latitudes between 30°N and 20°N.

Relative abundance of five rice stem borer species on each crop of a triple rice pattern in Iloilo, Philippines

Relative abundance of five rice stem borer species on each crop of a triple rice pattern in Iloilo, Philippines