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Weed Management in Rainfed Upland Rice Fields under Varied Agro-Ecologies in Nigeria

Rice science 2022年第4期29卷 328-339页

作者： Oyebanji O.ALAGBO Oluyemisi A.AKINYEMIJU bhagirath s.chauhan Department of Crop Production and Protection Faculty of AgricultureObafemi Awolowo UniversityIle-Ife 220005Nigeria Department of Crop Soil and Pest ManagementOndo State University of Science and TechnologyOkitipupa 353Ondo-StateNigeria Queensland Alliance for Agriculture and Food Innovation/school of Agriculture and Food sciences The University of QueenslandGatton 4343QueenslandAustralia

The demand for rice to meet the dietary need in low-income countries is expected to witness an exponential rise as the population *** the rice demand domestically has remained challenging due to significant yield loss caused by several biotic and abiotic *** these factors,one of the most important is the high weed pressure that ravages the upland rice *** Nigeria,several independent weed control techniques,such as physical,chemical and cultural methods,have been recommended and adopted for weed control across varying rice upland ***,outcomes of these approaches when used independently have not consistently led to an increase in *** remains an outstanding deficit between the actual yield and the potential rice *** review aimed to identify potential research gaps,and quest effective and sustainable weed management strategies in smallholder upland rice farming systems in Nigeria.A critical analysis of studies suggests the potential of sustainable weed management practices if adopted and adapted smartly in different upland ecologies in *** of upland rice against weeds can be enhanced through strategic integration of weed competitive cultivars,optimum nitrogen application timings(within weed-free periods),uniform plant spacing,and high seeding rates,with conventional herbicide/manual weed control ***,such management practices can only be engaged where inputs are supplied on time and the technical know-how is extended to *** review equally highlights potential research gaps for further studies.

关键词： herbicide integrated weed management weed flora tillage practice rainfed upland rice

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Rice Husk Biochar Influences seedling Emergence of Junglerice(Echinochloa colona)and Herbicide Efficacy

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American Journal of Plant sciences 2013年第7期4卷 1345-1350页

作者： bhagirath s.chauhan Crop and Environmental sciences Division International Rice Research InstituteLos BanosPhilippines

The use of carbonized rice husk biochar improves the fertility and productivity of poor soils in rice-based cropping systems. However, biochar may also influence weed seedling emergence and the efficacy of soil-applied herbicides. Experiments were conducted in a screenhouse to evaluate the effect of biochar rates (0, 20, 40, and 80 t·ha?1) and seed burial depth (0, 1, and 2 cm) on seedling emergence of junglerice (Echinochloa colona) and the effect of biochar rates and pendimethalin (0, 500, 1000, and 1500 g·a.i.·ha?1) and pretilachlor doses (0, 300, 600, and 900 g·a.i.·ha?1) on seedling emergence and seedling biomass of junglerice. Data were analyzed using nonlinear regression. The burial depth to inhibit 50% of maximum seedling emergence was 0.76 cm when biochar was not added to soil and the depth increased with an increase in biochar rates for soil. similarly, compared with the soil with no biochar, the use of bichoar increased the pretilachlor dose to inhibit 50% of maximum emergence or biomass. The pretilachlor dose to inhibit 50% of maximum biomass of junglerice was 100, 130, 240, and 240 g·ha?1 when biochar was added at 0, 20, 40, and 80 t·ha?1. However, the efficacy of pendimethalin was not influenced by biochar rate. The results of this study suggest that rice husk biochar may increase weed seedling emergence from deeper burial depths and may decrease the efficacy of some soil-applied herbicides.

关键词： Biochar Emergence Efficacy Biomass Rice Asia

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Effect of Water stress on the Growth and Development of Amaranthus spinosus,Leptochloa chinensis,and Rice

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American Journal of Plant sciences 2013年第5期4卷 989-998页

作者： bhagirath s.chauhan seth B.Abugho Crop and Environmental sciences Division International Rice Research InstituteLos BanosPhilippines

Drought is the most important abiotic constraint in rainfed rice systems. In these systems, Amaranthus spinosus and Leptochloa chinensis are the dominant weed species, which may reduce the available water to rice by competition and cause water stress in the crop. Two studies were conducted in a greenhouse to evaluate the growth response of A. spinosus and rice and L. chinensis and rice to water stress. The water stress treatments were 12.5%, 25%, 50%, 75%, and 100% of field capacity and the plants were grown until weed maturity (i.e., 63 days from seeding). Rice plants did not survive at 12.5% and 25% of field capacity, but both weed species survived in all the treatments. Both weed species produced a significant number of tillers/branches and leaves even at the lowest soil water content. The maximum amount of total shoot biomass produced by weed plants was 2.5 to 3 times more than that of rice plants. The soil water content to achieve 50% of the maximum aboveground biomass was 47%-50% of field capacity for rice, whereas it was 39% and 31% of field capacity for A. spinosus and L. chinensis, respectively. A. spinosus plants responded to increasing water stress with increased leaf weight ratio, whereas the leaf weight ratio of L. chinensis decreased with increases in water stress. The ability of A. spinosus and L. chinensis to produce shoot biomass under water-stressed conditions suggests that weed management strategies are needed that can minimize weed survival in water-limited environments. These strategies may include the use of weed-competitive and drought-tolerant cultivars, high seeding rates, and optimum timing of fertilizers.

关键词： Biomass soil Moisture Weed Rainfed Drought

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Management of Volunteer Corn seedlings in Dry-seeded Rice

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American Journal of Plant sciences 2013年第12期4卷 2381-2385页

作者： bhagirath s.chauhan Jhoana L.Opena Weed science Crop and Environmental Sciences DivisionInternational Rice Research InstituteLos BanosPhilippines

The demand for corn is increasing in Asia for feed and biofuel. It is grown in the rice-corn cropping system. During harvest of corn, however, seeds drop on the soil surface and become problems as volunteer corn seedlings in the subsequent dry-seeded rice crop, in which the suppressive effect of standing water is absent. A study was conducted in screenhouse and field conditions to evaluate the effect of rice herbicides on the management of volunteer corn seedlings. In the screenhouse experiment, bispyribac-sodium at 0.030 and 0.045 kg·ai·ha-1 provided complete control of corn seedlings. Fenoxaprop + ethoxysulfuron and penoxsulam + cyhalofop did not provide effective control of corn seedlings. In the field, the sole application of bispyribac and sequential application of oxadiazon and bispyribac suppressed corn biomass by 60%-82% and 89%-91%, respectively, as compared with the nontreated control. The results of this study demonstrate that, in the absence of other management strategies, volunteer corn seedlings in dry-seeded rice systems can be managed by using bispyribac-sodium.

关键词： Management of Volunteer Corn seedlings in Dry-seeded Rice

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Effect of Plant Geometry on Growth and Yield of Corn in the Rice-Corn Cropping system

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American Journal of Plant sciences 2013年第10期4卷 1928-1931页

作者： bhagirath s.chauhan Jhoana L.Opena Weed science Crop and Environmental Sciences DivisionInternational Rice Research InstituteLos BanosPhilippines

The rice-corn cropping system is increasing in Asia in response to increased demand of corn for feed. A field study was conducted to evaluate the effect of plant geometry (row and plant to plant spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on growth and yield of corn. Plant height and leaf production per plant were not influenced by the plant geometry. spacing, however, influenced leaf area, aboveground shoot biomass, and yield of corn per unit area. Highest leaf area, shoot biomass, and yield (8.2 t·ha-1) were produced by plants grown at 50 × 20 cm spacing. The results of this study suggest that narrow rows and plant to plant spacing may increase grain yield by increasing crop growth rates. Plant geometry could be modified to improve yield of corn in the rice-corn cropping system, and thereby increase productivity of the system.

关键词： Row spacing Plant to Plant spacing Leaf Area Rice-Corn Cropping system

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Effect of Plant spacing on Growth and Grain Yield of soybean

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American Journal of Plant sciences 2013年第10期4卷 2011-2014页

作者： bhagirath s.chauhan Jhoana L.Opena Weed scientist and Assistant scientist Weed ScienceCrop and Environmental Sciences DivisionInternational Rice Research InstituteLos BanosPhilippines

In the Philippines, rice monoculture systems are common. Compared to these systems, the rice-soybean cropping system may prove more water-efficient and there is a trend of increasing soybean area in the response to water scarcity and need for crop diversification in the Philippines. A field study was conducted to evaluate the effect of row and plant to plant spacing (20 × 10, 20 × 5, 40 × 10, and 40 × 5 cm) on growth and yield of soybean. Plant height was not influenced by the plant geometry. spacing, however, influenced leaf area and shoot biomass of soybean. Plants grown at the widest spacing (i.e., 40 × 10 cm) produced lowest leaf area and shoot biomass at 6 and 12 weeks after planting. Leaf area and shoot biomass at other three spacing were similar. There was a negative and linear relationship between weed biomass and crop shoot biomass at 6 and 12 weeks after planting. Grain yield of soybean was not affected by plant geometry and it ranged from 1.3 to 1.9 t·ha-1 at different spacing.

关键词： Row spacing Plant to Plant spacing Leaf Area Weed Biomass

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Weedy Rice(Oryza sativa L.)Problem in Rice(Oryza sativa L.)Based Cropping systems in the Philippines

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American Journal of Plant sciences 2013年第12期4卷 2359-2366页

作者： Irene R.Tanzo Edwin C.Martin bhagirath s.chauhan Philippines Rice Research Institute(PhilRice) MaligayaMunozNueva EcijaPhilippines International Rice Research Institute(IRRI) Los BañosPhilippines

A study was undertaken in February 2012 to understand the knowledge and practices of rice farmers about weedy rice in two municipalities of Iloilo, Philippines. The specific objectives of the study were to establish what rice farmers know about weedy rice, examine rice farmers’ practices in managing weedy rice, and recommend policies on weedy rice management based on the results of the study. Farmers’ knowledge of weedy rice did not differ much between two villages. Results showed that 41% from the second most affected village and 33% from the most affected village thought that weedy rice cannot reduce the market value of the harvested rice. Majority of the farmers (68%) responded that awns can be absent in some weedy rice and about 40% of the farmers did not know that seeds of weedy rice have dormancy. Cutting the weedy rice panicles at harvest, as the best way of reducing weedy rice, was practiced by majority of the respondents (82%) from the most affected village. Our study suggests that there is a need to increase awareness about weedy rice among Asian farmers.

关键词： Knowledge Awareness Iloilo Weedy Rice

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A comprehensive investigation on nonlinear vibration and bending characteristics of bio-inspired helicoidal laminated composite structures

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 81-100页

作者： s.sAURABH R.KIRAN D.sINGH R.VAIsH V.s.chauhan school of Mechanical and Materials Engineering Indian Institute of Technology Mandi

Bio-inspired helicoidal composite laminates, inspired by the intricate helical structures found in nature, present a promising frontier for enhancing the mechanical properties of structural designs. Hence, this study provides a comprehensive investigation into the nonlinear free vibration and nonlinear bending behavior of bio-inspired composite plates. The inverse hyperbolic shear deformation theory(IHsDT) of plates is employed to characterize the displacement field, with the incorporation of Green-Lagrange nonlinearity. The problem is modeled using the C0finite element method(FEM), and an in-house code is developed in the MATLAB environment to solve it numerically. Various helicoidal layup configurations including helicoidal recursive(HR), helicoidal exponential(HE), helicoidal semi-circular(Hs), linear helicoidal(LH), and Fibonacci helicoidal(FH)with different layup sequences and quasi-isotropic configurations are studied. The model is validated, and parametric studies are conducted. These studies investigate the effects of layup configurations, side-to-thickness ratio, modulus ratios, boundary conditions, and loading conditions at different load amplitudes on the nonlinear vibration and nonlinear bending behaviors of bio-inspired composite plates. The results show that the laminate sequence exerts a substantial impact on both nonlinear natural frequencies and nonlinear bending behaviors. Moreover, this influence varies across different side-to-thickness ratios and boundary conditions of the bio-inspired composite plate.

关键词： finite element method (FEM) nonlinear Green-Lagrange inverse hyperbolic shear deformation theory (IHsDT) bio-inspired composite plate helicoidal O322

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Temperature-dependent aggregation of bio-surfactants in aqueous solutions of galactose and lactose:Volumetric and viscometric approach

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Chinese Journal of Chemical Engineering 2018年第5期26卷 1119-1131页

作者： s.chauhan Vivek sharma Maninder Kaur Poonam Chaudhary Department of chemistry Himachal Pradesh University

Modulation in the aggregation behavior of bio-surfactants （bile salts）, sodium cholate （NaC） and sodium deoxycholate （NaDC） in aqueous solutions of carbohydrates （galactose and lactose） have been investigated by measuring the density （ρ）, speed of sound （u） and viscosity （η） of the mixtures at different temperatures 293.15, 298.15, 303.15, 308.15 and 313.15 K. The density and speed of sound data have been used to calculate various volumetric and compressibility parameters such as apparent molar volume （Vφ）, isentropic compressibil- ity （κs）, apparent molar adiabatic compression （κs,φ） to get a better insight into the micellization mechanism of bile salts. Further, the viscosity data have been studied in the light of relative viscosity （ηr） and viscous relaxation time （τ）. some derived parameters such as free volume （νf）, internal pressure （πi） and molar cohesive energy （MCE） of NaC and NaDC in aqueous solution of saccharides have also been calculated from viscosity data in con- junction with density and speed of sound values. All the calculated and derived parameters provide qualitative information regarding the nature of interactions i.e. solute-solute, solute-solvent and solvent-solvent in the solution.

关键词： Density speed of sound Apparent molar volumelsentropic compressibility Viscosity Relative viscosity

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Enhanced thermoelectric performance in p-type ZrCosb based half-Heusler alloys employing nanostructuring and compositional modulation

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Journal of Materiomics 2019年第1期5卷 94-102页

作者： Nagendra s.chauhan sivaiah Bathula Avinash Vishwakarma Ruchi Bhardwaj Kishor Kumar Johari Bhasker Gahtori Ajay Dhar Academy of scientific&Innovative Research(AcsIR) CSIR-National Physical LaboratoryNew Delhi 110012India Division of Advanced Materials and Devices Metrology CSIR-National Physical LaboratoryDr.K.S.Krishnan MargNew Delhi 110012India

ZrCosb based half-Heusler(HH)alloys have been widely studied as a p-type thermoelectric(TE)material for power generation applications in the mid-temperature ***,their intrinsically high thermal conductivity has been found to be detrimental for the improvement in their thermoelectric figure-of-merit(ZT),which presently is far below *** the current work,a state-of-the-art ZT~1.1 at 873 K was realized in an optimized composition of nanostructured Zr1-xHfxCosb_(0.9)sn_(0.1) HH alloys by employing compositional modulation ***-by-grain compositional variations,which leads to a substantial increase in its power factor coupled with a concurrent decrease in its thermal *** reduction in the phonon mean-free-path is observed on Hf substitution,which is comparable to the average crystallite size(~25 nm),thus leading to a very low thermal conductivity of~2.2Wm^(-1)K^(-1) at 873 K,which is amongst the lowest reported in HH *** TE device characteristics,estimated using cumulative temperature dependence model for quantitative evaluation of TE performance,yielded an output power density of~10 Wcm2 with a leg efficiency of~10%in the optimized composition of nanostructured Zr_(1-x)Hf_(x)Cosb_(0.9)sn_(0.1) HH alloys,which is comparable to the reported efficiencies of other state-of-the-art TE materials.

关键词： Half Heuslers Iso-electronic Waste heat recovery Mid-temperature Efficiency Compositional modulation

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