Summer Rice Research Articles

Arsenic contamination in cropping systems under varying irrigation sources in the deltaic plain of India

ABSTRACTA field experiment was conducted in an arsenic endemic area of West Bengal, India (22°57ʹN, 89°33ʹE) in 2010–2012 to understand different prevalent cropping systems of the area as to nature of arsenic uptake by the crops and influence of different sources of irrigation water. The experiment was laid out in split plot design consisting two irrigation managements [I1: irrigation with shallow tube well (STW) and I2: irrigation from harvested pond water (PW)] in main plot and four cropping systems in sub plot were C1: pea- summer rice- cowpea, C2: potato- green gram- elephant foot yam (EFY), C3: wheat- jute- winter rice and C4: French bean- sesame- winter rice. Irrigation from PW recorded less arsenic uptake compared to STW. Arsenic uptake was minimum with French bean- sesame- winter rice (C4), followed by potato – green gram – EFY (C2). System equivalent yield was the highest with C2. The highest return was recorded with C2 and the return per dollar (USD) investment was the maximum with C1, followed by C2. Potato- green gram- EFY (C2) proved to be the better option for the farmers in arsenic contaminated area with greater yield potential, highest return per dollar investment and less arsenic uptake.

English

English

Climate resilient technological interventions to ensure food security in flood affected area – An experience from NICRA village, Dhubri, Assam

The study was conducted in villages of Dhubri district in Assam under National Innovation on Climate Resilient Agriculture (NICRA) project implemented by Krishi Vigyan Kendra, Dhubri during 2013 to 2015. The villages are situated under Bilasipara sub-division in the district ‘Dhubri’ of Assam, India on 26° 15. 425´ to 26° 16.570´ N latitude and 90° 14.034´ to 90° 18.040´ E longitude at an elevation of 128 ft from mean sea level. Recurrent floods has been the principal constraints in food production in these villages affecting mainly winter ( Kharif ) rice during the growing season as well as summer rice ( Boro and Ahu ) at the time of maturity. The prevailing weather patterns of the area were observed to have a strong bearing on the occurrence, intensity and magnitude of floods. About 71 per cent of total rainfall occurs during monsoon period (June to September), the winter being virtually dry leaving little scope for growing any Rabi crop. To ensure rice production to climatic variability leading to flood, site specific climate resilient technologies such as staggered planting rice variety ‘Gitesh’, flood escaping, short duration HYV rice ‘Luit’ for post and pre-flood situation, submergence tolerant rice variety ‘Swarna Sub 1’ and mid duration HYV of rice ‘Joymati’ during preflood situation were tested and demonstrated in the project villages. It was necessary to observe the performance of these varieties to the climatic vulnerability as well as farmer’s acceptability. The average yield of the rice variety ‘Gitesh’ (45 days aged seedlings), ‘Luit’ (post flood situation), ‘Luit’ (pre-flood situation), ‘Swarna Sub 1’ and ‘Jomati’ were found to be 40 to 42, 26.3 to 36, 23.35 to 31.39, 33 to 45 and 42.37 to 50.76 q per hectare, respectively. As a result of the study and demonstration to endure recurrent flood and climatic variability, the newly introduced winter rice varieties, Gitesh has spread over the highest area in the project villages (90.00%) followed by ‘Swarna Sub 1’ (75.00 %) and ‘Luit’ (66.67 %) due to flexibility in seedling age facilitating delayed transplanting, submergence tolerance upto 14 days and allowance for transplanting after recession of flood, respectively.

COMPARATIVE EFFICACY OF HERBICIDES IN WEED CONTROL AND ENHANCEMENT OF PRODUCTIVITY AND PROFITABILITY OF RICE

SUMMARYWeed management is the major challenge to the success of boro rice (rice grown during Dec–Jan to May–Jun, also known as summer rice) in Southern Asia. Herbicide seems to be a cost effective and strategic tool from an agronomic view point to control weeds; however, herbicide application can potentially interfere with soil enzyme activity and microbial biomass carbon (MBC). A field study was conducted in 2012/13 and 2013/14 to evaluate the performance of sole and combined application of different pre-emergence herbicides in comparison to manual weeding in boro rice. Lowest weed density, biomass and highest weed control efficiency (~83%) were recorded with the pyrazosulfuron ethyl, causing higher grain yield (6.7 Mg ha−1 in 2012/13 and 4.5 Mg ha−1 in 2013/14) than treatments with chlorimuron + metsulfuron-methyl, bensulfuron methyl + pretilachlor, butachlor fb 2,4D, butachlor and cono-weeder. Among, the herbicidal treatments butachlor caused lower grain yield and higher weed density and biomass when compared to the others. Although grain yield was highest in weed-free treatments but net returns and (B:C) benefit cost ratio was highest for pyrazosulfuron ethyl due to high cost of hand weeding. After 15 days of herbicide application, lowest microbial biomass carbon was recorded with bensulfuron methyl + pretilachlor, whereas lower values of dehydrogenase and fluorescein diacetate activities were observed with the application of chlorimuron + metsulfuron-methyl at 15 days after herbicide application. Our results suggest that pyrazosulfuron ethyl is one broad-spectrum and economically effective herbicide for controlling weeds as an alternative to labour consuming hand weeding in boro rice cultivation.

Comparative studies on different methods of summer rice crop establishment under drip irrigation in relation to water use, growth and yield

Comparative studies on different methods of summer rice crop establishment under drip irrigation in relation to water use, growth and yield

Sustaining the productivity of sesame (Sesamum indicum L.) grown in Onattukara sandy soil through the application of sulphur and boron

Sulphur and boron have been found to act in a synergistic manner for enhancing the yield and quality of sesame (Sesamum indicum L.). As it is the choice crop of farmers in the summer rice fallows of Onattukara, field experiments were laid out in factorial RBD with four levels each of sulphur and boron with the variety Thilarani. The levels of sulphur tried were 0 kg S ha-1, 7.5 kg S ha-1, 15.0 kg S ha-1 and 30.0 kg S ha-1 and 0 kg B ha-1, 2.5 kg B ha-1, 5.0 kg B ha-1 and 0, 2.5, 5.0 and 7.5 kg B ha-1 for boron which were applied as gypsum and borax, respectively. The incubation study, designed to understand the release pattern of nutrients reveled that highest quantity of sulphur and boron were available during the 30th day of incubation and there after showed a decreasing trend. Application of sulphur @ 30 kg ha-1 and boron @ 7.5 kg ha-1improved the available nutrient status of Onattukara soil. The nutrient use efficiency of sulphur was highest at 30 kg ha-1 and that for boron it was 2.5 kg ha-1. It also registered a significant positive impact on enhancing the yield and yield attributes of sesame in such a way that the highest rates of both the nutrients registered maximum yield from the crop in both the years.

Water Scarcity and Irrigation Efficiency in Egypt

This study provides quantitative assessments of the impacts of efficiency enhancement for different types of irrigation water under water scarcity conditions. It employs a single country CGE (STAGE 2) model calibrated to an extended version of a recently constructed SAM for Egypt 2008/09. The SAM segments the agricultural accounts by season and by irrigation scheme, including Nile- and groundwater-dependent as well as rain-fed agricultural activities. The simulations show that Egypt should manage potential reductions in the supply of Nile water with more efficient irrigation practices which increase the productivity of Nile water, groundwater and irrigated land. The results suggest a more ambitious plan to boost irrigation efficiency for summer rice would be desirable in order to outweigh any potential shrinkage in output and exports. Furthermore, even doubling all non-conventional water resources is not sufficient to compensate the potential adverse impacts of Nile water losses. This highlights the importance of irrigation efficiency for the Egyptian economy.

Comparative Effectiveness of Organic Substitution in Fertilizer Schedule: Impacts on Nitrous Oxide Emission, Photosynthesis, and Crop Productivity in a Tropical Summer Rice Paddy

Studies on replacement of inorganic fertilizer with organic residues to improve crop productivity and their impact on greenhouse gas emission from agricultural soil merit more attention. Two-year field experiments were conducted to study the impact of different organic residues with varied carbon (C)/nitrogen (N) ratios as substitutes of chemical fertilizer on emission reduction of nitrous oxide (N2O) and crop yield from a tropical summer rice paddy of India. Five treatments comprising of conventional N fertilizer (NPK), cow manure (CD), rice straw (RS), poultry manure (PM), and sugarcane bagasse (SCB) were applied in a rice field to estimate N2O emission. Application of CD (at 10 t ha−1) resulted in maximum reduction of seasonal N2O emissions (15 %) over NPK, RS, PM, and SCB. Application of CD and RS enhanced leaf photosynthetic rate and caused maximum utilization of photosynthates towards developing grains as evident from grain filling ability and higher grain yield. Substitution of NPK with organic residues enhanced soil nutrient availability in terms of C and N resulting in improved soil fertility and to some extent influenced soil nitrogen processes which in turn reduced N2O emissions. We conclude that suitable management of soil in agricultural ecosystem can reduce the emission of N2O and protect and preserve the soil health without compromising the agronomic productivity reducing the use of chemical fertilizer and maintaining the sustainability of rice ecosystem as evident from lower carbon equivalent emissions (CEE) and higher carbon efficiency ratio (CER) at CD in rice paddies in the present study.

Drainage, no-tillage and crop rotation decreases annual cumulative emissions of methane and nitrous oxide from a rice field in Southwest China

Permanently flooded rice fields, a special kind of all year-round flooded rice fields in China, where the crop system is summer rice (Oryza sativa ‘Q You 6′) with winter fallow, contribute to both CH4 and N2O emissions. To investigate their CH4 and N2O emissions over a whole year (November 2009 to October 2010) and responses to long-term tillage-cropping systems, four treatments after the conversion of such rice fields were examined: conventional tillage with a single summer rice and floodwater winter fallow (CTRF) or drained winter rapeseed (Brassica napus ‘W You 25′) (CTRR), no-tillage narrow- or wide-ridge with a rice and rapeseed rotation (NTNRR or NTWRR). Results showed that CTRF emitted the highest CH4 owing to permanently flooding water layer and higher soil organic carbon concentrations. Compared to CTRF, CH4 emissions under other three tillage-cropping systems were decreased not only in the winter season but also in the rice-growing season. In contrast, N2O emissions over a whole one-year rice-rapeseed rotation cycle were almost equivalent to each other under these four tillage-cropping systems. Also compared to CTRR, the two no-tillage-cropping systems tended to enhance CH4 while decrease N2O emissions, though with insignificant effects. The annual cumulative emissions of CH4 and N2O were highest under CTRF (1.07±0.20 kg CO2-eqha−1kg−1 yield) and significantly decreased under CTRR, NTNRR and NTWRR (0.59±0.10, 0.67±0.05 and 0.58±0.09 kg CO2-eqha−1kg−1 yield, respectively), indicating that the summer rice-winter rapeseed rotation system, irrespective of tillage management, rather than the summer rice-winter fallow system, had achieved the objective of higher yields with less greenhouse gas emissions. These results demonstrate that the no-tillage wide-ridge with a rice and rapeseed rotation (NTWRR) is the most efficient management in terms of decreasing CH4 and N2O emissions in Southwest China.

Salinity intrusion and rice production in Red River Delta under changing climate conditions

This study was carried out to identify the vulnerability of rice production to salinity intrusion arising from climate change in Giao Thuy, a coastal district of Nam Dinh Province, located in Red River Delta in Vietnam. From the analysis of historical climate data at Nam Dinh city, both mean maximum and minimum temperatures increased by about 0.3 and 0.1 °C per decade, respectively, during the period of 1961–2010. Salt concentration of the river water was higher at the irrigation gate closer to river mouth (Con Nhat) than at the upstream gate (Ha Mieu), which generally increased from 2003 to 2012, with the average maximum concentration up to 2.13 % at Con Nhat gate in 2010. The salt water concentration in the riverside field outside the dyke reached 3.6 %, while among the fields within dyke the salinity was only 0.7 % at maximum in January 2013, and the values were higher in paddy fields close to the dyke than far from the dyke. Average yield among the selected 27 fields from 2011 summer to 2013 spring rice was higher in spring rice (748 g m−2) but lower in summer rice (417 g m−2) mainly due to unfavorable weather such as cold spell at flowering and flood at harvesting time. Rice yield was lowest in general in the most downstream commune Giao Thien, and was significantly lower in field located close to the dyke than those far from the dyke. This spatial variability of rice yield may not be directly attributable to salinity, but to the other factors such as shift of irrigation intake gate to further upstream and/or different management such as less input of N fertilizer and use of traditional local variety.

Biochar use for climate-change mitigation in rice cropping systems

This study estimated the climate change effects of alternative rice production systems in North Vietnam with different residue management options, using Life Cycle Assessment (LCA). The traditional practice of open burning of residues (System A) was compared with the alternative of converting residues to biochar, which was returned to the same land area from which the residues were obtained (System B). Pyrolytic cook-stoves and drum ovens were assumed to be used by households to produce biochar, and the cook-stoves produced heat energy for cooking. The annual rate of biochar applied was determined by the amount of biochar produced from the straw and husk available. We assumed that agronomic effects of biochar increased with each annual biochar application until reaching maximum benefits at 18 Mg ha−1, which takes eight years to be produced in pyrolytic cook-stoves and drum ovens. The largest contributor to the carbon footprint of rice at the mill gate, was CH4 emissions from soil, in both systems. Biochar addition reduced the carbon footprint of spring rice and summer rice by 26% and 14% respectively, compared with System A, in the first year of application. These values substantially increased to 49% and 38% after eight years of biochar addition. The climate effect of System B was most sensitive to the assumed suppression of soil CH4 emissions due to biochar application.

Manure, biogas digestate and crop residue management affects methane gas emissions from rice paddy fields on Vietnamese smallholder livestock farms

Greenhouse gas (CH4 and N2O) emissions from rice paddy fields amended by differently treated manure and crop residue inputs [fresh manure (FM), composted manure (CM), liquid biogas digestate from manure (D), D mixed with biochar (D + B) or D mixed with rice straw and composted before application (CD + RS)], were compared in a field experiment, also including two mineral nitrogen fertiliser controls (N1, N2). The trial was performed on a degraded soil in Bac Giang Province in northern Vietnam with a three-crop per year rotation (summer rice–maize–spring rice). CH4 and N2O fluxes from the two rice crops were measured using static chambers. Fluxes of N2O were below or close to the detection limit at nearly all sampling times in both seasons and therefore considered negligible. However, the CH4 emissions were significant and their temporal pattern differed markedly between the rice seasons. In the summer rice season, the D + B + N1 and D + N1 treatments had significantly lower cumulative CH4 emissions (156 and 162 kg CH4 ha−1 crop−1) than CM + N1, CD + RS + N1 and FM + N1 treatments (217, 283 and 288 kg CH4 ha−1 crop−1, respectively). In the spring rice season, CH4 emissions were generally much lower, and the D + B + N1 and D + N1 treatments emitted significantly less CH4 (44 and 72 kg CH4 ha−1 crop−1) in comparison with treatments amended with FM + N1, CD + RS + N1 and CM + N1 (89, 124 and 137 kg CH4 ha−1 crop−1, respectively). Treatments amended with D + B + N1 or D + N1 therefore had the lowest emissions of methane per unit of rice grain yield.

Nitrogen management in a rice–wheat system in the Taihu Region: Recommendations based on field experiments and surveys

Excessive use of mineral nitrogen (N) fertilizer has been a common practice in the high-yielding rice–wheat double-cropping system in the Taihu Region of southeastern China. As a consequence of high N balance surpluses and low N use efficiencies (NUEs), nitrogen losses to water bodies and to the atmosphere are high. Field experiments on five replicate farmers’ field sites were conducted in southern Jiangsu Province over three consecutive rice–wheat double-crop rotations with three different N fertilization treatments (‘conventional’ (farmers’ practice), ‘reduced’ (by 23% for rice and 32% for wheat) and zero N application). A parallel survey was carried out involving 43 farmers’ households, in order to calculate standard gross margins (SGM) and to conduct an environmental assessment of the rice–wheat farming system in the Taihu Region. The results of the field experiment showed that a distinct reduction in fertilizer N application rates to summer rice and winter wheat crops is possible without significant decrease in mean grain yields. Mean grain yields for the entire double-crop rotation were 14.7Mgha−1yr−1 under the conventional N fertilization practice and 14.1Mgha−1yr−1 under reduced N fertilization. A significant increase in NUEs could be achieved in most years and crops under reduced N fertilization compared to farmers’ practice, and N balance surpluses were significantly decreased from 142kgNha−1 to less than 60kgNha−1yr−1 under the reduced N fertilization regime. The residual mineral N contents in the soil profiles after winter wheat harvest showed a decreasing tendency over time with a reduction of N fertilization. Mineral N contents in fertilized fields were significantly higher than on the zero N plots. Concentrations of NH4+-N in soil extracts from the puddled layer during the summer rice in 2010 showed significant differences between the two N fertilization treatments and the zero N plots. Results of the agro-economic survey showed that production of rice was 50% more profitable than that of wheat, and that fertilizer costs made up less than 20% in the rice season, but almost 50% of the total production costs during the wheat season. It can be concluded that N losses to the environment can be efficiently decreased by reducing the overall N fertilization rates without any risk of decline in grain yield and related income for farmers. Based on the field experiments and investigations, a reduction in N fertilizer application rates by 15–25% for summer rice and by 20–25% for winter wheat, compared to present levels is recommended.

Economic assessment of technology adoption in summer rice production in the Konkan region (M.S.) – methodology for excess adoption

An attempt has been made in this article to study the economic assessment of technology adoption in case of summer rice, and to suggest the methodology for measurement of technology adoption in case of excess adoption. Study is based on primary data collected from 120 summer paddy growers from Raigad district of Maharashtra. An attempt is also made to suggest a methodology for excess use of inputs up to any level which is more than the recommended level of input use. The adoption index in case of excess adoption gives conceptually appropriate results. As the per cent use of inputs more than the recommended level increases, the technology adoption index also decreases in same proportion. The adoption index value ranges from zero to 100. It attains maximum value at recommended level. It increases up to recommended level and decreases thereafter as per the proportionate excess use of inputs in a given data set. The study revealed that seed was utilized in excess quantity in all groups and use of fertilizers was more in higher adoption group. Input gap was ranging from 33 per cent to 48 per cent which was higher in low adoption group. The total yield gap was 10.42 quintals (22.53 %). However, yield gap I and yield gap II were low, such as 2.75 and 7.67 quintals, respectively. The increase in yield was 17.25 per cent more in high adoption group than the check (low adoption). The per quintal cost in high adoption group was lesser by 24 per cent (i.e. Rs. 888/-) than low adopters group (Rs. 1170/-). It is concluded that in addition to increase in adoption of technology by more number of farmers, the extent of adoption also need to be increased for increasing productivity of rice, reducing yield gap and per quintal cost of rice production.

Farmers’ Adaptation to Rainfall Variability and Salinity through Agronomic Practices in Lower Ayeyarwady Delta, Myanmar

The paper analyses factors influencing the agricultural adaptation practices in embankment and non-embankment areas of lower Ayeyarwady delta based on the information collected through a survey of 240 sampled households mostly practicing rice farming. Farmers in both areas have adopted several agronomic practices to adapt with rainfall variability and soil and water salinization due to sea level rise. A multivariate probit model employed to estimate the simultaneous interdependent decisions by farm households explained the factors influencing the adaptation of rice farmers to respond to the rainfall variability and salinity. Irrespective of correlation signs, the most significant determinants in adaptations of non-embankment area are farm size, farm income, non-farm income, training and lowland followed by educational level, family agricultural labor, land ownership, farming experience and the institutional credit. In the embankment area, five variables out of 12; namely, farm size, farm income, training frequency, credit and lowland are most influential on the adoption of agricultural adaptation practices. The poor linkage of extension and training programs reflected the poor lowland soil condition and cultural practices. Although double cropping of rice in monsoon and summer has provided higher cropping intensity and farm income, it has promoted the soil salinity and environmental unsustainability. Policy instruments are therefore suggested for an effective implementation of soil conservation and integrated farming system in lowland rainfed rice-based cropping system.

A seven-year study on the effects of fall soil tillage on yield-scaled greenhouse gas emission from flood irrigated rice in a humid subtropical climate

In southern Brazil, flood irrigated rice is grown during the summer, while a self-reseeding ryegrass is grown during the winter months without irrigation. Soil tillage operations that incorporate the rice and ryegrass residues into the soil are performed only in the spring season, which may increase methanogenesis due to higher substrate availability in reduced subsurface soil layers. It was hypothesized that anticipating the soil tillage from spring to the fall season reduces yield-scaled greenhouse gas emissions during the summer rice season due to lower availability of C compounds to methanogenic bacteria in subsurface soil layers. A seven-year study was conducted to determine soil methane (CH4) and nitrous oxide (N2O) emissions, partial global warming potential [pGWP=(CH4*25)+(N2O*298)], rice yields, and yield-scaled pGWP emissions (yield-scaled pGWP=pGWP/yield) from flood irrigated rice under spring and fall tillage treatments. No significant effect of tillage treatments on soil N2O emissions and rice yields was detected. When averaged across treatments and growing seasons (GSs), rice yield was 7.9 Mgha−1 GS−1, whereas cumulative N2O emissions were 3.65kg N2Oha−1 GS−1. Soil CH4 emissions were responsible for 91.5% of pGWP. The spring tillage treatment resulted in an earlier and larger first peak of CH4 efflux, likely due to higher labile C availability originated from the rice and ryegrass biomass decomposition in subsurface soil layers. In contrast, in the fall tillage treatment the easily decomposable compounds of the rice residue was utilized during the winter months, which combined with the ryegrass biomass kept on the soil surface resulted in lower labile C availability in subsurface soil layers. The fall tillage treatment significantly reduced cumulative CH4, pGWP and yield-scaled pGWP emissions by 24, 21, and 25%, respectively. Averaged across GSs, CH4, pGWP and yield-scaled pGWP emissions for the fall and spring tillage treatments were 316 and 417kg CH4ha−1 GS−1, 8.6 and 10.9Mg CO2eqha−1 GS−1, and 1.06 and 1.41kg CO2eqkg−1 grain, respectively. Our results indicate that shifting soil tillage operations from spring to fall can successfully mitigate yield-scaled pGWP emissions from regional flooded rice fields.

Effect of seaweed saps on growth and yield improvement of transplanted rice in old alluvial soil of West Bengal

On summer rice, foliar spray was applied thrice at different concentrations (0, 2.5, 5.0, 7.5, 10.0 and 15.0%, v/v) of seaweed extracts (namely, Kappaphycus sp. and Gracilaria sp.) along with the recommended dose of fertilizer (RDF). The highest grain yield was recorded with the applications of 15% Kappaphykus sap + RDF, followed by 15% Gracilaria sap + RDF extract resulting in 41.47 and 34.99% increases, respectively compared to the control. The maximum straw yield was also achieved with 15% seaweed extract application. Improved nutrient uptake (N, P and K) was also observed with seaweed extract applications. DOI: http://dx.doi.org/10.3329/bjb.v43i1.19746 Bangladesh J. Bot. 43(1): 53-58, 2014 (June)

Improving agronomic practices to reduce nitrate leaching from the rice–wheat rotation system

Winter wheat–summer rice rotation with unique dry–wet cycle water regime is one of the most general cropping systems in the Yangtze Delta, which might favor NO3−-N leaching into shallow groundwater due to high fertilizer-N input with low N use efficiency. To alleviate the detrimental impacts caused by N leaching, it is necessary to apply improved management practices. Therefore, the objectives of the present study are to investigate characteristics of N leaching under drained upland crop-flooded rice rotation and illustrate the effectiveness of an improved agronomic practice for mitigating NO3−-N leaching. N leaching measured in situ for the control (CK), conventional (CT), and improved (IT) treatments for one rice–wheat rotation. Improved fertilization and crop cultivation managements have been applied to the IT treatment in an integrated manner, including low N fertilization rate, high fertilization frequency, and dense planting. During the rice-growing season, NO3–-N and dissolved organic N (DON) were the predominant forms of N in percolation water, and contributed over 25% and 59% to TN, respectively. NO3–-N and TN concentrations in percolation water and leaching losses did not differ significantly (p>0.05) between treatments. N leaching occurred mainly during the early stage of rice seedling transplanting. During the wheat-growing season, N in percolation water was predominantly in the form of NO3–-N, and accounted for over 64.5–82.9% of TN. N fertilization significantly increased NO3–-N and TN concentrations in percolation water. Nitrate and TN leaching losses from the IT treatment (1.15 and 1.38kg Nha−1, respectively) were smaller than the CT treatment (1.34 and 1.76kg Nha−1, respectively). The majority of N leaching losses for wheat occurred during the period from late February to final harvest. The IT treatment exhibited no significant effect on wheat yield, but significantly (p<0.05) increased rice yield (8.60Mgha−1 compared to 8.06Mgha−1) relative to the CT treatment. Compared with the conventional management practice, the improved management practice appeared to be effective in reducing N leaching and increasing grain yield under the rice–wheat rotation.

Adaptation strategies for rice cultivation under climate change in Central Vietnam

This study investigates the impact of climate change on winter and summer rice (Oryza sativa) yield and evaluates several adaptation measures to overcome the negative impact of climate change on rice production in the Quang Nam province of Vietnam. Future climate change scenarios for time periods in the 2020s, 2050s and 2080s were projected by downscaling the outputs of the General Circulation Model (GCM), Hadley Centre Coupled Model, version 3 (HadCM3) A2 and B2 scenarios. The AquaCrop model was used to simulate the impact of future climates on rice yield. The minimum and maximum temperature of the province is projected to increase by 0.35–1.72 °C and 0.93–3.69 °C respectively in future. Similarly, the annual precipitation is expected to increase by 9.75 % in the 2080s. Results show that climate change will reduce rice yield from 1.29 to 23.05 % during the winter season for both scenarios and all time periods, whereas an increase in yield by 2.07 to 6.66 % is expected in the summer season for the 2020s and 2050s; relative to baseline yield. The overall decrease of rice yield in the winter season can be offset, and rice yield in the summer season can be enhanced to potential levels by altering the transplanting dates and by introducing supplementary irrigation. Late transplanting of rice shows an increase of yield by 20–27 % in future. Whereas supplementary irrigation of rice in the winter season shows an increase in yield of up to 42 % in future. Increasing the fertilizer application rate enhances the yield from 0.3 to 29.8 % under future climates. Similarly, changing the number of doses of fertilizer application increased rice yield by 1.8 to 5.1 %, relative to the current practice of single dose application. Shifting to other heat tolerant varieties also increased the rice production. Based on the findings, changing planting dates, supplementary irrigation, proper nutrient management and adopting to new rice cultivars can be beneficial for the adaptation of rice cultivation under climate change scenarios in central Vietnam.

Abundance and species composition of rice green leafhopper (Hemiptera: Cicadelladae) in different ecosystems

The abundance, incidence pattern and species composition of green leafhopper (GLH) in seedbed, rice field and light trap were studied in three rice growing seasons in Bangladesh during 2004 and 2005. Five species of GLH were recorded. These were Nephotettix virescens, N. nigropictus, N. malayanus, N. parvus and N. cincticeps. The first two species were most important as their presence were higher in number almost all the year round. More GLH was observed in 2005 compared to 2004 in all habitats. The GLH population was higher in seedbed than transplanted rice. Seedbed of both the year prevailed highest number of GLH than transplanted rice. Among 5 species of GLH N. nigropictus was found higher in summer and winter rice seedbed during 2005. Nephotettix virescens was dominant in summer rice seed bed in both the year and transplanted monsoon rice field in the year 2005. The number of other 3 species of GLH was comparatively low in all the season and habitats. Temperature and rainfall influenced the population of GLH. The fluctuation of GLH population in the rice field did not always represent the fluctuation of light trap catches. The abundance of 5 GLH species in the order of N. virescens> N. nigropictus> N. malayanus> N. cincticeps > N. parvus.