Browsing by Subject "Rice"

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Development of multifunctional unmanned aerial vehicles versus ground seeding and outplanting: What is more effective for improving the growth and quality of rice culture?
(2022) Qi, Peng; Wang, Zhichong; Wang, Changling; Xu, Lin; Jia, Xiaoming; Zhang, Yang; Wang, Shubo; Han, Leng; Li, Tian; Chen, Bo; Li, Chunyu; Mei, Changjun; Pan, Yayun; Zhang, Wei; Müller, Joachim; Liu, Yajia; He, Xiongkui
The agronomic processes are complex in rice production. The mechanization efficiency is low in seeding, fertilization, and pesticide application, which is labor-intensive and time-consuming. Currently, many kinds of research focus on the single operation of UAVs on rice, but there is a paucity of comprehensive applications for the whole process of seeding, fertilization, and pesticide application. Based on the previous research synthetically, a multifunctional unmanned aerial vehicle (mUAV) was designed for rice planting management based on the intelligent operation platform, which realized three functions of seeding, fertilizer spreading, and pesticide application on the same flight platform. Computational fluid dynamics (CFD) simulations were used for machine design. Field trials were used to measure operating parameters. Finally, a comparative experimental analysis of the whole process was conducted by comparing the cultivation patterns of mUAV seeding (T1) with mechanical rice direct seeder (T2), and mechanical rice transplanter (T3). The comprehensive benefit of different rice management processes was evaluated. The results showed that the downwash wind field of the mUAV fluctuated widely from 0 to 1.5 m, with the spreading height of 2.5 m, and the pesticide application height of 3 m, which meet the operational requirements. There was no significant difference in yield between T1, T2, and T3 test areas, while the differences in operational efficiency and input labor costs were large. In the sowing stage, T1 had obvious advantages since the working efficiency was 2.2 times higher than T2, and the labor cost was reduced by 68.5%. The advantages were more obvious compared to T3, the working efficiency was 4 times higher than in T3, and the labor cost was reduced by 82.5%. During the pesticide application, T1 still had an advantage, but it was not a significant increase in advantage relative to the seeding stage, in which operating efficiency increased by 1.3 times and labor costs were reduced by 25%. However, the fertilization of T1 was not advantageous due to load and other limitations. Compared to T2 and T3, operational efficiency was reduced by 80% and labor costs increased by 14.3%. It is hoped that this research will provide new equipment for rice cultivation patterns in different environments, while improving rice mechanization, reducing labor inputs, and lowering costs.
Genotypic responses of upland rice to an altitudinal gradient
(2012) Shrestha, Suchit Prasad; Asch, Folkard
Adaptation strategies are required for crops to cope with changing climate. The impact of climate change on crop production is not straight forward to predict as extreme events comprise multiple combination of abiotic stresses and their impact differs in crop physiological growth stages. The mechanism on how new abiotic stress combinations translate into phenology and yield, and which cultivars are better adapted is yet unclear. Crop growth models are available that have been parameterized and validated for some aspects of possible climate change scenarios but in view of complex interactions crop responses to climate change are difficult to predict. On the other hand, prediction of the complex ideotype trait combinations may be interesting for breeders but physiological models are required that are well validated for the target environments. In upland rice grown under rainfed conditions without surface water accumulation methane emission is negligible and therefore greenhouse gas emission much lower compared to irrigated paddy rice systems. In addition, growing demand for rice and the increasing pressure on irrigated land leads to development of upland rice areas to supplement irrigated rice. Therefore, this study investigates genetically diverse upland rice genotypes from a wide range of origins across altitudinal gradient locations. The main objective of this study is to investigate genotypic responses of upland rice to different environments in order to calibrate crop growth models, which allow the evaluation of effects of climate change on upland rice systems. Multi-locational field (three locations: 1625, 965 and 25 m asl) trials comprising non-replicated phenological plots with five sowing dates (monthly staggered) in two consecutive years creating thirty different environments, and replicated physiological yield trials with two sowing dates (monthly staggered; early and late sowing) in two consecutive years creating twelve different environments were established in Madagascar. Ten contrasting upland rice genotypes were included in both field trials. Meteorological data were recorded on a daily basis during trial periods. Developmental stages were observed in the phenological plots; in the physiological plots yield and yield components were recorded. In addition, greenhouse trials were conducted with one upland rice genotype subjected to seven N-supply levels in a hydroponic system at the University of Hohenheim in order to understand the relationship between chlorophyll index, photochemical reflectance index and chlorophyll fluorescence parameters. Various statistical tools were applied to analyse field and greenhouse data sets. The phenological trial showed that duration to flowering was 117, 81 and 67 d in high (HA), mid (MA) and low (LA) altitudinal locations respectively. 90% of the total variance was explained by location when pooled over genotype, location, sowing dates and year. In HA, factors such as genotype, sowing date and year equally contributed to the observed variability whereas in MA year was the most determining factor and genotype had no significant contribution. Similarly, in LA sowing date was the main influencing factor and year had no significant effect. Aggregated data over locations, sowing dates and years indicated that each degree Celsius rise in mean air temperature decreased crop duration by 5 to 9 days depending upon genotype. Basic genotypic thermal constants Tbase ranged from 9.8 to 13.9 °C and Tsum from 816 to 1220 °C d within the selected genotypes. Cold tolerant genotypes were less affected by lower Tmin (14 °C) at booting to heading stage regarding spikelet sterility in HA, whereas others were highly affected at 15 °C (cold stress). Similarly, both cold sensitive and tolerant genotypes were affected by Tmax (above 30 °C) at flowering in MA and LA locations (heat stress). Grain yield and yield components were highly affected by location, year, sowing date, and genotypes and the interactions between these yield-determining factors were obvious. In HA, early sown cold tolerant genotypes had more than 5 t ha-1 grain yield and one month delay in sowing led to highly reduced yield whereas other genotypes had very poor yield on both sowing dates due to cold stress. In MA, yield difference between sowing date and genotypes was small (4.3 - 4.9 t ha-1). Grain yield in LA was vulnerable due to frequent tropical storms. Yield stability analysis showed that cold tolerant genotypes had above average stability. AMMI model for grain yield showed that environment and genotype by environment interactions were highly significant. Yield components determined during specific development stages of the genotype such as tillers per hill and percentage of filled spikelets were mainly influenced by environment, spikelets per panicle and thousand grain weight were influenced by genotype, and percentage of productive tillers was equally influenced by both genotype and environment. PCA biplots showed that all HA environments were equally influenced by all weather parameters with minimum air temperature having the strongest positive influence on genotypic performance. In all MA environments genotypic performance in all phenophases was strongly and positively influenced by rainfall, and strongly and negatively influenced by vapour pressure deficit, solar radiation and potential evapotranspiration. In the LA environments, main weather parameters influencing genotypic performance were maximum temperature and high rainfall accompanied by strong winds. The field measured SPAD values of the upper canopy leaves reflected the location specific N-remobilization and leaf senescence levels after flowering. Similarly, PRI values showed the abiotic stress responses among development stages and locations along the altitudinal gradient. These readings showed that genotypes were efficient in radiation use and N-remobilization after flowering in MA. The unsynchronized relationship between source (leaf) and sink (grain) explained the yield penalty. Emphasis on identification of morpho-physiological traits contributing to cold tolerance should be placed for further breeding. We conclude that genotypic responses of upland rice cultivars differed across altitudinal gradients. Genotypes that are well adapted in HA can easily be adapted in MA without yield decrease. But genotypes well adapted in MA may show a huge yield penalty in HA due to lower temperature during reproductive phase and consequently reduced sink formation. Frequent tropical storms and high temperature reduced yield potential in LA. Therefore, HA has a large potential for the future food security considering climate change scenarios. At present, MA is favorable for upland rice production systems, whereas LA is highly vulnerable and is expected to be even more vulnerable in future. Those results on genotype-specific responses to environmental conditions allow further improvement of crop models such as RIDEV and SAMARA (synthesis of SARRAH and EcoMeristem), which can be used to test a number of phenotypic traits x environments combinations to define ideotypes of upland rice varieties adapted to changing climate and cropping calendars. Genotypic responses of phyllochron, biomass production and crop growth rate, and radiation use efficiency across altitudinal gradients will be included to parameterize these models. In this regard, collaborations with AfricaRice, CIRAD and IRRI are ongoing.
Greenhouse gas emissions from rice production in the Vietnamese Mekong River Delta as affected by varietal selection and water management
(2023) Vo, Thi Bach Thuong; Asch, Folkard
The topic of this dissertation deals with rice production, the predominant source of daily nourishment for more than half of the worlds population. Rice production is directly affected by global climate change through aggravating climatic conditions, but is also one of the major sources of greenhouse gases (GHG) in the agricultural sector. The latter aspect is investigated in 4 publications by assessing the factors contributing to emissions, the quantification of GHG emissions across different scales, and possible mitigation of GHG emissions. In totality, these studies aim at bridging the gap between field measurements to national extrapolations in view of both GHG inventories and future mitigation programs. In terms of methodologies, the publications compiled in the following chapters represent a broad spectrum ranging from field measurements to meta-analysis, but they all deal with the emission of methane (CH4) which is generated in rice fields due to the unique feature of ‘semi-aquatic’ soils. The publications based on newly conducted field measurements also a nitrous oxide (N2O) which is a potent GHG emitted typically emitted from rice fields in low quantities. Chapter 2 (Vo et al. 2018) compiles field measurements from the Vietnamese Mekong River Delta (MRD) which accounts for more than 50% of the country’s rice production. Emission factors (EFs) are used to estimate total emissions associated with the area of rice production. The Intergovernmental Panel on Climate Change (IPCC) has given the default EFs that are based on global averages as Tier 1 approach. However, the IPCC guidelines encourage national reporting institutions to conduct field measurements of GHG emissions and to determine country-specific EFs as the basis of the Tier 2 approach. Tier 2 further accounts for the fact that emissions may also be highly variable within a given country by requesting for disaggregation of EF at a sub-national scale. Therefore, the most recent GHG inventories for Vietnam are based on region-specific EFs under the IPCC Tier 2 approach, which is implemented using national activity data (i.e., national average cultivation period of rice and harvested area). In Chapter 2, we developed the specific EFs for different hydrological sub-zones and growing seasons in the MRD to achieve disaggregated EFs that could be used for the National Communications submitted to the United Nations Framework Convention on Climate Change (UNFCCC). Due to the distinct bio-physical condition and cropping cycle, the results show the lowest emissions in the saline sub-zone. While alluvial, acid sulfate soils had intermediate levels, the highest emissions were found in the deep flood sub-zone. In Chapter 3 (Vo e al. 2018), we expanded the geographical scope of the GHG assessment to the entire country. This meta-analysis of CH4 data covers 73 cropping seasons at 36 field sites across the rice-growing areas of Vietnam under the IPCC’s baseline conditions (i.e., continuously flooded, no organic amendments) in the three main cropping seasons. As an output of this study, a structured database contained the location and season of each measurement as well as site-specific bio-physical factors and crop management at the site scale. In the next step, we developed disaggregated EFs for different zones and cropping seasons across the country that can be used for future reporting commitments of Vietnam as part of a more accurate Tier 2 assessment. The calculated EFs were generally higher than the IPCC defaults and the values used for Vietnam’s 3rd National Communications for the North, Central, and South Vietnam. Chapter 4 (Vo et al. 2023) has to be seen in the context of Vietnam’s climate change policy that aims at reducing GHG emissions from rice production. Mitigation in rice production will be crucial for Vietnam because CH4 from rice accounts for about 15 % of the national GHG which is more than the entire transport sector even without considering CO2 and N2O emissions along the rice value chain. Previous studies have assessed the potential practices by changes in farming practices, namely water, nutrient, and straw management, and almost uniformly concluded that Alternate Wetting and Drying (AWD) is the most promising strategy for achieving a sizable mitigation of GHG emissions. Given the intense rainy season in southeast Asia, however, the precipitation is often too high to implement this water regime and will not provide any economic benefit from water saving. In turn, it is important to consider other mitigation strategies such as the selection of low-emitting cultivars. We conducted a field screening of 20 rice varieties that was expanded by assessing the interactive effect of variety selection and AWD. An experimental layout with 120 plots (based on 3 replicates) was required to assess this interaction of variety and water management in the field using the closed chamber method to collect air samples followed by lab analysis (using a gas chromatograph) to quantify the CH4 and N2O concentrations. The results of this study confirmed that GHG emissions from rice fields are dominated by CH4 emissions whereas N2O emissions were negligible. Compared with IPCC default values, the data set from two dry seasons yielded higher emissions under a baseline of continuous flooding (EF = 2.96 kg CH4 ha-1 d-1) and lower Scaling Factors (SF) of AWD (SF = 0.4). Chapter 5 (Asch et al. 2023) deals with the agronomic aspects of both AWD and variety selection and their implications on the economic viability of future mitigation efforts. While AWD is more efficient in reducing CH4 emissions than variety selection, this water management practice resulted in a slight yield decrease in our field study. Given the limited applicability of AWD, the selection of varieties is a much more adaptable approach and is also beneficial in terms of farmers’ adoption because it does not require any crop management changes. However, this strategy could also impact profits since the lowest-emitting variety may not have the highest rice yields. In the context of future mitigation programs in the MRD, the dry season allows good control of the water table, so AWD should be the core of any mitigation effort. Variety selection on the other hand should be targeted in those seasons and locations that do not allow draining the fields. In turn, low-emitting varieties should become an integral part of future mitigation programs to supplement AWD within a systematic out scaling. In terms of economic trade-offs for the farmers, we assumed a scenario with compensation derived from the still premature carbon markets. The potential profit increments are very low and not attractive if distributed to farmers directly, but may collectively be used for investments in rural development by government agencies for benefitting farmers indirectly, e.g. by improving the irrigation infrastructure.
Influences on the performance of the stripper rotor in rice
(2002) Tado, Caesar Joventino M.; Kutzbach, Heinz Dieter
Rice is the most important food crop in many countries of Asia. In the Philippines, it is the staple food for more than 80% of the people while 70% of our population depend on rice farming and marketing for livelihood. However, despite the importance of rice in the lives of the Filipinos, production has not been able to consistently meet their needs. The ever-growing population continues to exert tremendous pressure on the rice farmers to produce more. The principle of stripping, that is, collecting the grains without harvesting the straw, presents a bright prospect in mechanical harvesting technology. A kinematic analysis of the stripper rotor during operation was made with a newly designed stripper test rig.
Photosynthesis, quantum requirements, and energy demand for crop production in controlled environments
(2020) Schmierer, Marc; Asch, Folkard
In this work, energy costs for LED (light emitting diodes) lighting of a virtual plant stand exhibiting C3photosynthesis have been calculated via a model considering the quantum demand to build-up dry matter and energy efficiency of state-of-the art LEDs. Optimistic and pessimistic scenarios have been calculated by taking into account uncertainties regarding the H+/ATP stoichiometry of photosynthesis and different management strategies for indoor plant production. Energy costs were between 265 and 606 kWh for a production cycle ranging over 100 days and resulting in 2500 g dry matter per square meter for the optimistic and the pessimistic scenario respectively. The conversion efficiencies from electrical energy to energy bound in phytomass at the end of the production cycle were 2.07 % and 4.72 % (pessimistic and optimistic scenario, respectively). This was lower than the theoretical maximum values calculated for C3 plants that are given as 9.5 % in the literature. However, when the losses that occur during the conversion from electrical energy to light energy were excluded and only the efficiency of the conversion from incident light energy to phyto-energy was calculated, values increased to 4.0 and 9.1 %. The differences between the optimistic and the pessimistic scenario was caused by decreased photorespiration via carbon dioxide fertilization, which increased the conversion efficiencies by 38 %, followed by different assumptions about the H+ requirement for ATP production (34 %) and an increased rate of active absorption of light energy (24 %). Considering cumulative as well as feedback effects of all of the mentioned parameters, the conversion efficiency in the optimistic scenario was 2.3 times higher than in the pessimistic scenario. A system for measuring gas-exchange of whole plants or plant stands was developed in order to be able to investigate and improve the above mentioned management strategies in the future. CO2 sensors and temperature and humidity sensors were used to detect water loss and CO2. Readily available off-the-shelf electronic and mechanical materials were used in order to build a low-cost system that can be used in high throughput experiments. The results indicate that around 90 % of the transpirational water was detected by the system. We conclude that parts of the transpirational water condensed on the surfaces thus not leaving the chamber. When checking the accuracy of the H2O and CO2 sensors using an industry quality infrared gas analyser (IRGA), we found significant deviations from the values given by the IRGA and used this data for calibration of the CO2 sensors. The responses of the CO2-sensors were also linearly coupled to the H2O concentrations (about -0.1 % ppm CO2 / ppm H2O). A regression analysis was performed and the coefficients were used to correct the sensor readings. Since LEDs exhibit a higher energy-to-light ratio when operated at lower light levels, we tested a very small growing gibberellin (GA) deficient super dwarf rice genotype in a climate chamber experiment under different illumination levels and different levels of nitrogen supply to assess its suitability for crop production in artificial environments. A 25 % reduction in illumination lead to a 75 % reduction in yield, mainly due to a 60 % reduction in formed tillers and 20 % reduction in kernel weight, and an 80 % reduction in illumination caused total yield loss. Whereas leaf area under reduced illumination was significantly lower, only marginal changes in the dimensions of single leaves were observed. Photosynthesis at growing light conditions was not different between control plants and plants under 75 % illumination. This was explained by a higher photochemical efficiency under lower light conditions and a reduced mesophyll resistance. Therefore, we conclude that this genotype is an interesting candidate for crop production in vertical plant production systems, especially because of its short stature and the absence of shade avoidance mechanisms, such as leaf elongation, that would complicate production in small-height growing racks under low-light conditions. Nitrogen concentrations of 2.8 and 1.4 mmol L-1 in the nutrient solution lead to no differences in plant growth. We conclude that a nitrogen concentration of 1.4 mmol L-1 is sufficient for this genotype under the light intensities that were applied here. A software tool for simulations of photosynthesis in the python programming language was developed. The software implements a classical Farquhar-von CaemmererBerry (FvCB) model of leaf photosynthesis coupled with a model for the estimation of stomatal behaviour dependent on environmental conditions. We want to emphasize that the use of such models is essential to understand the complex interactions between plant growth, leaf photosynthesis and the environment. Knowledge on those relationships is the key to improve the efficiency of plant production in controlled environments.
Sustaining rice productivity through weather‐resilient agricultural practices
(2023) Rahman, Niaz Md. Farhat; Malik, Waqas Ahmed; Baten, Md. Azizul; Kabir, Md. Shahjahan; Rahman, Mohammad Chhiddikur; Ahmed, Rokib; Hossain, ABM Zahid; Hossain, Md. Mofazzel; Halder, Tuhin; Bhuiyan, Md. Khairul Alam; Khan, Mohammad Ashik Iqbal; Khan, Raihanul Haque; Ahasan, Nazmul; Piepho, Hans‐Peter
BACKGROUND: Enhancing productivity and profitability and reducing climatic risk are the major challenges for sustaining rice production. Extreme weather can have significant and varied effects on crops, influencing agricultural productivity, crop yields and food security. RESULTS: In this study, a comparative evaluation of two crop management systems was performed involving farmers adopting a weather forecast-based advisory service (WFBAS) and usual farmers’ practice (FP). WFBAS crop management followed the generated weather forecast-based advice whereas the control farmers (FP) did not receive any weather forecast-based advice, rather following their usual rice cultivation practices. The results of the experiments revealed that WFBAS farmers had a significant yield advantage over FP farmers. With the WFBAS technology, the farmers used inputs judiciously, utilized the benefit of favorable weather and minimized the risk resulting from extreme weather events. As a result, besides the yield enhancement, WFBAS provided a scope to protect the environment with the minimum residual effect of fertilizer and pesticides. It also reduced the pressure on groundwater by ensuring efficient water management. Finally, the farmers benefited from higher income through yield enhancement, reduction of the costs of production and reduction of risk. CONCLUSION: A successful and extensive implementation of WFBAS in the rice production system would assist Bangladesh in achieving Sustainable Development Goal 2.4, which focuses on rice productivity and profitability of farmers as well as long-term food security of the country. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.