Thermogravimetric analysis and the optimisation of bio-oil yield from fixed-bed pyrolysis of rice husk using response surface methodology (RSM)

The effects of pyrolysis temperature, heating rate, particle size, holding time, and gas flow rate were investigated to optimize bio-oil yield from rice husk pyrolysis. Thermogravimetric analysis showed thermal degradation of hemicellulose, cellulose and lignin, indicating faster decomposition of cellulose compared to lignin. The optimisation process was analysed by employing central composite design (CCD) in response surface methodology (RSM) using Design Expert Version 7.5.1 (StatEase, USA). A two-level fractional factorial was initially carried out and followed by RSM. The statistical analysis showed that pyrolysis temperature, heating rate, particle size and holding time significantly affected the bio-oil yield. By utilising response surface method, these four factors were investigated, analysed and optimal conditions were obtained at pyrolysis temperature of 473.37 °C, heating rate of 100 °C/min, particle size of 0.6 mm and holding time of 1 min. Confirmation runs gave 48.30% and 47.80% of bio-oil yield compared to 48.10% of predicted value. Furthermore, the pyrolytic bio-oils obtained from fixed-bed pyrolysis were examined using gas chromatographic/mass spectroscopy (GC/MS), Fourier transform infrared (FTIR) methods, elemental analyzer, pH probe and bomb calorimeter.     

Effect of surface cover on the reduction of runoff and agricultural NPS pollution from upland fields

In this study, two types of simulations were performed. First, indoor rainfall simulation revealed that runoff ratio (0–63.3 %) decreased dramatically with surface cover, compared with no surface cover condition (55–85.3 %), and sediment load and concentration also decreased. With additions of PAM, sawdust, and rice hull to rice straw mat, the runoff ratio decreased to 52.8, 36.6, and 53.2 %, compared with only rice straw mat condition (runoff ratio of 63.3 %). When gypsum was added, no runoff was observed in case of rainfall intensity of 30 mm/h. Under 60 mm/h rainfall condition, 50 % or more runoff reduction was observed. These could be explained in that surface cover reduces detachment of soil particles and keeps infiltration rate by reducing surface sealing with detached soil particle which could happen under non-surface cover condition. Second, when rice straw mat was applied to soybean field, no runoff was observed until rainfall intensity of 5.8 mm/h or greater, while runoff was observed with rainfall intensity of 1.5 mm/h at no surface covered soybean field. In addition, 89.7–99.4 % of pollutant reductions were observed with rice straw mat at the soybean field. When rice straw mat with additions of wood shaves was applied to Chinese cabbage and radish fields, 4.3–75.8 % of runoff reductions and 28–80.8 % of pollutant reductions were observed. In case of Chinese cabbage, 122.1 % yield increase was observed and 153.4 % yield increase in case of radish.     

Climate risk and agricultural technology adaption: evidence from rice farmers in the Ayeyarwady River delta of Myanmar

Paddy and Water Environment - Crop income can be raised in two ways: one way is to increase crop productivity and the other is to grow high-value crops that could be sold at high prices in the...     

Evaluation of HYDRUS-2D model to simulate the loss of nitrate in subsurface controlled drainage in a physical model scale of paddy fields

Agriculture is a major source of nitrogen usage and release to environment. Due to the effect of water movement on solute transport, investigating the effect of different management scenarios of irrigation and drainage could be useful for reducing nitrate loss and environmental pollution. This study is a scientific attempt to assess the ability of HYDRUS-2D model to simulate the effect of subsurface controlled drainage on nitrate loss of paddy fields. So, two physical models with difference in depth of subsurface controlled drainage (40 and 60 cm) were constructed. The tanks were filled with loam silty soil texture and then transplanted rice. 90 kg/ha potassium nitrate fertilizer was added in two stages of rice growth. Mid-season drainage was applied 26 days after transplantation. After 17 days, drains were closed again and applied flooded irrigation with 5-cm water stagnant layer above soil surface. During experiment, nitrate concentration of drain water was measured. HYDRUS-2D was calibrated with measured data in 60 cm drain depth and validated with 40 cm drain depth. HYDRUS-2D could simulate nitrate concentration with the coefficient of determination 0.95 and 0.89 in calibration and validation stages, respectively. The comparison between the volume of drain water and nitrate concentration from the drains in the depths of 40 and 60 cm indicated lower nitrate load in depth of 40 cm. The results obtained proved that the presence of hardpan layer in depth of 25 cm rather than the absence of it causes increase in 3 % of average nitrate concentration and reduce in 17 % of water discharge.     

APEX-Paddy model simulation of hydrology,total nitrogen,and rice yield for different agricultural activities in paddy fields

Paddy and Water Environment - Existing agro-hydrological models to explore the effects of paddy management practices on hydrology and water quality suffer from multiple shortcomings because they...     

Analysis of runoff in the Han River basin by SSARR model considering agricultural water

This study begins to address the need for a runoff model that is able to simulate runoffs at control points in a dam’s upper and lower stream during the seasons of high and low water levels. We need to establish a synthetic management plan on water resources considering the runoff at the upper and lower streams to effectively manage the limited water resources in Korea. For this reason, we classified the Han River Basin into 24 sub-basins and arranged a great amount of rainfall data using 151 rainfall observation stations so as to prepare for the spatial distribution of precipitation. We chose several dams as subjects for this study, which includes the Chungju Regulating Reservoir, Soyang, Chungju, Hoengseong, Hwacheon, Chuncheon, Euiam, Cheongpyeong, and Paldang Dams as main controlling points. Also, we made up input data of this model, selecting the Streamflow Synthesis and Reservoir Regulation (SSARR) model as a runoff model in the Han River Basin. We performed a sensitivity analysis of parameters using hydrological data from the year 2002. And as a result, the findings of this study showed that, among many parameters related to the basin runoff, the following have revealed greater sensitivity than any other parameters: soil moisture index-runoff percent, baseflow infiltration index-baseflow percent, and surface-subsurface separation. On the basis of the above sensitivity analysis, we have used hydrological data between 2001 and 2002 when drafts and floods broke out in Korea to verify and calibrate the parameters of the SSARR model. Furthermore, we verified and calibrated the 2000 data using corrected parameters and performed an analysis of annual water balance in the Han River Basin from 1996 to 2005 considering agricultural water.     

Future potential impacts of climate change on agricultural watershed hydrology and the adaptation strategy of paddy rice irrigation reservoir by release control

This study is to assess the climate change impact on the temporal variation of paddy rice irrigation reservoir water level from the future evaluated watershed inflow, and to suggest an adaptation method of the future reservoir water level management for stable water supply of paddy irrigation demands. A 366.5 km² watershed including two irrigation reservoirs located in the upper middle part of South Korea was adopted. For the future evaluation, the SLURP model was set up using 9 years daily reservoir water level and streamflow records at the watershed outlet. The average Nash-Sutcliffe model efficiencies for calibration and validation were 0.69 and 0.65, respectively. For the future climate condition, the NIES MIROC3.2 hires data by SRES A1B and B1 scenarios of the IPCC was adopted. The future data were downscaled by applying Change Factor statistical method through bias-correction using 30 years past weather data. The results of future impact showed that the future reservoir storages of autumn and winter season after completion of irrigation period decreased for 2080s A1B scenario. Considering the future decrease of summer and autumn reservoir inflows, the reservoir operation has to be more conservative for preparing the water supply of paddy irrigation, and there should be a more prudent decision making for the reservoir release by storm events. Therefore, as the future adaptation strategy, the control of reservoir release by decreasing in August and September could secure the reservoir water level in autumn and winter season by reaching the water level to almost 100% like the present reservoir water level management.     

Long-term evaluation of the BMPs scenarios in reducing nutrient surface loads from paddy rice cultivation in Korea using the CREAMS-PADDY model

Curbing nutrient loads from rice cultivation has been an issue for the water quality management of surface water bodies in the Asian monsoon region. The objectives of this study were to develop paddy BMP scenarios and to evaluate their effectiveness on nutrient loads reduction using long-term model simulation. Totally five BMP scenarios were developed based on the three paddy farming factors of drainage outlet height, fertilizer type, and application amount and were compared with conventional practices. CREAMS-PADDY model was chosen for the paddy nutrient simulation, and two-year field experimental data were used for the model calibration and validation. The validated model was used to evaluate the developed BMP scenarios for the 46 years of simulation period. The observed nutrient loads were 15.2 and 1.45 kg/ha for nitrogen and phosphorus, respectively, and mainly occurred by early season drainage and rainfall runoff in summer. The long-term simulation showed that the soil test-based fertilization and drainage outlet raising practice were the two most effective methods in nutrient loads reduction. The combination of these two resulted in the greatest loads reduction by 29 and 37 % for T-N and T-P, respectively (p value < 0.001). Overall the effectiveness of the BMP scenarios was decreased in the wet season. As the conclusion, outlet height control and soil nutrient-based fertilization were suggested as the effective practices in paddy loads reduction and their combination can be a practicable BMP scenario for the paddy nutrient management.     

Evaluation of the water-quality dynamics in a eutrophic agricultural pond by using a one-box ecosystem model considering several algal groups

The Okubo pond is an agricultural pond located in the Itoshima area of Fukuoka Prefecture, Japan. It was constructed for irrigating a nearby cultivated area. A monitoring program from August 11 to November 26, 2008, suggested the risk of eutrophication in the water body. The high total nitrogen concentration (1.34 mg/l), high total phosphorus concentration (0.06 mg/l) and extreme oxygen depletion (2 mg/l on 5 November 2008) exceeded the Japanese standards for paddy irrigation water. Furthermore, luxuriant algal blooming in October indicated a hypereutrophic status according to the OECD (1982) criteria. In this study, a one-box ecosystem model was developed to obtain an insight into the seasonal variations in the algal concentrations and chemical components of the Okubo pond with the aims of protecting its aquatic ecosystem and maintaining its water quality. The model was based on a completely mixed system and included 12 water-quality indices: green algae, blue-green algae, diatoms and dinoflagellates, cryptophytes, zooplankton, particulate organic matter, dissolved organic matter, phosphate–phosphorus, ammonia–nitrogen, nitrite–nitrogen, nitrate–nitrogen, and dissolved oxygen. The monitoring data were used to verify the model simulation. Model evaluation suggested good agreement between the predicted and the observed data for the seasonal variations in the algal, nutrient, and dissolved oxygen concentrations. To determine the sensitivity of the model parameters, a sensitivity analysis was conducted leading to the conclusion that the optimal temperature, growth rate, and respiratory rate of the four algal groups, especially the ideal temperature for blue-green and green algae are the most influential factors determining the variability affecting the model inference. From the model simulation, the water temperature and nutrient concentration were considered to be the key limiting factors controlling alternative algal blooms in this period.     

Economic returns from fungicide application to control husk spot of macadamia in Australia is influenced by spray efficiency,rates and costs of application

Fungicides are commonly applied as prophylactic sprays, with the expectation of increased yield and kernel quality, to control husk spot of macadamia in Australia. However, economic benefits from fungicide applications to control husk spot have rarely been quantified. We investigated the effectiveness, efficiency and economic returns of fungicide spray applications for husk spot control using three different spray application volumes and two dose rates of tank mixtures of carbendazim and cupric hydroxide under commercial macadamia orchard conditions. Husk spot incidence and severity were significantly (P < 0.001) different among the treatments and between the two years. In both years, the rate of fruit abscission was highest in the untreated control followed by low spray application volumes, but reduced with increasing spray volume. The quality and value of nut-in-shell increased when nut abscission was delayed. Poor quality and low nut-in-shell value of $2.85 kg⁻¹ in 2010 and $2.12 kg⁻¹ in 2011 were obtained in the untreated control trees that abscised early in the harvest period compared with the average nut-in-shell value of $2.95 kg⁻¹ in 2010 and $2.46 kg⁻¹ in 2011 in the fungicide treated trees. Gross margins for each fungicide treatment schedule compared to the untreated control averaged over both years showed positive contributions of 20%, 10% and 6% for the high, moderate and low dilute rate volume applications, respectively. Our data further indicates that dilute rate applications at higher volume may be more beneficial and cost-effective than concentrate rate applications in husk spot control programs. Overall, harvest yield increased by 11%–33% when husk spot was controlled using fungicide sprays compared to no fungicide spray applications. The benefit-cost ratios revealed highly significant benefits for the implementation of husk spot management programs.     

A model driven by crop water use and nitrogen supply for simulating changes in the regional yield of rain-fed lowland rice in Northeast Thailand

Climate change will have significant impacts on the rain-fed rice production ecosystem, and particularly on the ecosystem’s hydrology and water resources. Under rain-fed lowland conditions, substantial variations among fields in grain yield are commonly observed, but a method that can account for field-scale yield variability to produce regional-scale yield estimates is lacking, thereby limiting our ability to predict future rice production under changing climate and variable water resources. In this study, we developed a model for estimating regional yields of rain-fed lowland rice in Northeast Thailand, by combining a simple crop model with a crop calendar model. The crop model incorporates the effects of two important resources (water and nitrogen) on crop growth. The biomass accumulation is driven by water use, whereas the nitrogen supply determines canopy development and thereby constrains crop water use. Accounting for the wide range of planting dates and the strong photoperiod-sensitive characteristics of rice varieties through the calendar model is an essential component in determining regional yield estimates. The present model does not account for the effects of mid-season drought or flooding, but was nonetheless able to explain the spatial and temporal yield variations at the province level for the past 25 years. Thus, it can be used as a prototype for simulating regional yields of rain-fed lowland rice.     

A simple method for squeezing juice from rice stems and its use in the high-throughput analysis of sugar content in rice stems

Sugar content in rice (Oryza sativa L.) stem is an agronomically important trait for rice used in straw silage or whole-crop silage. However, the mechanisms underlying sugar accumulation in rice stems remain unclear, mainly due to the time-consuming method for measuring sugar content. Here, we established a simple method for squeezing stem juice from rice plants, similar to that used during breeding selection in sugarcane or sorghum. The Brix value of the stem juice, which can easily be measured using a portable refractometer, significantly correlated with the soluble sugar contents in the stem juice and tended to correlate with those in stem tissues. This indicates that the Brix value of the stem juice can be used for estimating the sugar content in rice stems. This simple estimation method will be a useful tool for high-throughput analysis of sugar content in rice stems during mutant screening, QTL analysis, and breeding selection.     

Digestion of rice straw and oil palm fronds by microflora from rumen and termite bacteria, in vitro

The digestion and Volatile Fatty Acid (VFA) production from rice straw and oil palm fronds by cellulolytic bacteria isolated from the termite Coptotermes curvignathus were investigated. The bacteria were Acinetobacter strain Raminalimon, Enterobacter aerogenes strain Razmin C, Enterobacter cloacae strain Razmin B, Bacillus cereus strain Razmin A and Chryseobacterium kwangyangense strain Cb. Acinetobacter strain Raminalimon is an aerobic bacterium, while the other species are facultative anaerobes. There were significant differences (p<0.05) among the bacteria for Dry Matter (DM) lost and acetic acid production from rice straw and Acinetobacter strain Raminalimon showed the highest activity. The facultative bacteria C. kwangyangense strain Cb (cfu mL(-1) 231 x 10(-6), OD: 0.5), E. cloacae (cfu mL(-1) 68 x 10(-7), OD: 0.5) and E. aerogenes (cfu mL(-1) 33 x 10(-7), OD: 0.5) were used for digestion study with the rumen fluid microflora. The in vitro gas production technique was applied for the comparative study and the parameters measured were pH, gas (volume), dry matter lost, acetic acid, propionic acid and butyric acid concentrations. pH was not significantly (p<0.05) different among the five treatments. The bacterium C. kwangyangense strain Cb showed the highest activity (p<0.05) for DM lost, acetic acid, propionic acid and butyric acid production from rice straw when compared to the other bacterial activities. There was no significance (p<0.05) difference between the three bacteria for the dry matter lost of oil palm fronds but the production of Volatile Fatty Acids (VFA) was significantly (p<0.05) high in the treatment which was inoculated with C. kwangyangense strain Cb. The Gen Bank NCBI/EMBL accession numbers for the bacterial strains are EU332791, EU305608, EU305609, EU294508 and EU169201.     

Characterization of some biological control agents from rice seeds in China and in the Philippines

It is well known that rice seed contains large amount of seedborne bacterial pathogens. However, little is known about antagonistic bacteria of the rice seed.     

Characterization of some biological control agents from rice seeds in China and in the Philippines

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Characterization of Pseudomonas spp.and related bacteria from rice seeds in the subtropics and the tropics

To explore the bacterial diversity for sustain-able management of the major rice diseases,asurvey of bacterial diversity of rice seed wasconducted in Luzon Island of the Philippines(the tropics)and in Zhejiang Province of China(the subtropics),during 1993-1998.One hun-dred sixteen(0.5kg/sample)and 129(1kg/sample)seed samples were collected from the subtropics and the tropics,respectively.Morethan 3000 bacterial isolates were picked and examined under the UV light for their fluores-cence.After colony morphological,pathogeni-cal,and some bacteriological tests,816 non-pathogenic bacteria isolates were selected forfurther identification using a numeric taxono-     

Water supply from pearl millet by hydraulic lift can mitigate drought stress and improve productivity of rice by the close mixed planting

The authors have proposed the close mixed planting technique using mixed seedlings of two different crop species that results in close tangling of their root systems. Especially, the combination of drought-adaptive upland crops (e.g. pearl millet or sorghum) and flood-adaptive lowland crop of rice would be beneficial to overcome the drought and flood conditions and to reduce the risks of crop failure. In our previous studies, we found that upland crop yield losses by flood stress was mitigated by mix-cropped rice, owing to the oxygen gas released from the rice roots into the aqueous rhizosphere. In the present study, we conducted two experiments to assess whether mixed cropping a drought-resistant cereal, pearl millet, would improve the performance of co-growing drought-susceptible crop, rice under drought conditions. In the field experiment, some grains were obtained from the rice plants mix-cropped with pearl millet under drought condition. However, no rice matured in the single cropping system. In the model experiment using deuterium analysis, it was confirmed that water absorbed by pearl millet roots from deep soil layer was utilized by rice, suggesting that mix-cropped rice could withstand drought stress and complete grain filling using water released into the upper soil layer by hydraulic lift.