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Search Results: 1 - 10 of 325879 matches for " Bhagirath S. Chauhan "
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Rice Husk Biochar Influences Seedling Emergence of Junglerice (Echinochloa colona) and Herbicide Efficacy  [PDF]
Bhagirath S. Chauhan
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.47164
Abstract:

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

Fertilizer Placement Affects Weed Growth and Grain Yield in Dry-Seeded Rice (Oryza sativa L.) Systems  [PDF]
Bhagirath S. Chauhan, Seth B. Abugho
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.46155
Abstract:

A study was conducted in a split-plot design to evaluate the effect of fertilizer placement method on weed growth and grain yield in a dry-seeded rice (DSR) system. Main-plot treatments were four fertilizer placement methods: between narrow rows (between 15-cm-wide rows of the pattern 25-15-25 cm), between uniform rows (between 20-cm-wide rows), within uniform rows, and surface broadcast. Subplot treatments were three weed control methods: herbicide-treated, nontreated, and weed-free. Weed biomass was greater in the nontreated plots than in the herbicide-treated plots. Herbicide application reduced weed biomass by 89% to 99% compared with the nontreated control. Fertilizer placement did not influence weed biomass in the herbicide-treated plots; however, it greatly influenced biomass in the nontreated plots. Fertilizer placement on the surface increased weed biomass (69 -71 g·m2) compared with the placement of fertilizer below the soil surface (37 -57 g·m–2). Fertilizer placement did not influence weed density and biomass at 60 days after planting. Nontreated plots yielded 700 to 2080 kg·ha–1. Grain yield was similar between the herbicide-treated (2660-3250 kg

Effect of Water Stress on the Growth and Development of Amaranthus spinosus, Leptochloa chinensis, and Rice  [PDF]
Bhagirath S. Chauhan, Seth B. Abugho
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.45122
Abstract:

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

Effect of Plant Geometry on Growth and Yield of Corn in the Rice-Corn Cropping System  [PDF]
Bhagirath S. Chauhan, Jhoana L. Ope?a
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.410237
Abstract:

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.

Effect of Plant Spacing on Growth and Grain Yield of Soybean  [PDF]
Bhagirath S. Chauhan, Jhoana L. Ope?a
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.410251
Abstract:

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.

Management of Volunteer Corn Seedlings in Dry-Seeded Rice  [PDF]
Bhagirath S. Chauhan, Jhoana L. Ope?a
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.412294
Abstract:

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.

Seed Germination Ecology of Feather Lovegrass [Eragrostis tenella (L.) Beauv. Ex Roemer & J.A. Schultes]
Bhagirath S. Chauhan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079398
Abstract: Feather lovegrass [Eragrostis tenella (L.) Beauv. Ex Roemer & J.A. Schultes] is a C4 grass weed that has the ability to grow in both lowland and upland conditions. Experiments were conducted in the laboratory and screenhouse to evaluate the effect of environmental factors on germination, emergence, and growth of this weed species. Germination in the light/dark regime was higher at alternating day/night temperatures of 30/20 °C (98%) than at 35/25 °C (83%) or 25/15 °C (62%). Germination was completely inhibited by darkness. The osmotic potential and sodium chloride concentrations required for 50% inhibition of maximum germination were -0.7 MPa and 76 mM, respectively. The highest seedling emergence (69%) was observed from the seeds sown on the soil surface and no seedlings emerged from seeds buried at depths of 0.5 cm or more. The use of residue as mulches significantly reduced the emergence and biomass of feather lovegrass seedlings. A residue amount of 0.5 t ha-1 was needed to suppress 50% of the maximum seedlings. Because germination was strongly stimulated by light and seedling emergence was the highest for the seeds sown on the soil surface, feather lovegrass is likely to become a problematic weed in zero-till systems. The knowledge gained from this study could help in developing effective and sustainable weed management strategies.
Weedy Rice (Oryza sativa L.) Problem in Rice (Oryza sativa L.) Based Cropping Systems in the Philippines  [PDF]
Irene R. Tanzo, Edwin C. Martin, Bhagirath S. Chauhan
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.412292
Abstract:

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.

Effect of Weed Management and Seed Rate on Crop Growth under Direct Dry Seeded Rice Systems in Bangladesh
Sharif Ahmed, Muhammad Salim, Bhagirath S. Chauhan
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0101919
Abstract: Weeds are a major constraint to the success of dry-seeded rice (DSR). The main means of managing these in a DSR system is through chemical weed control using herbicides. However, the use of herbicides alone may not be sustainable in the long term. Approaches that aim for high crop competitiveness therefore need to be exploited. One such approach is the use of high rice seeding rates. Experiments were conducted in the aman (wet) seasons of 2012 and 2013 in Bangladesh to evaluate the effect of weed infestation level (partially-weedy and weed-free) and rice seeding rate (20, 40, 60, 80, and 100 kg ha?1) on weed and crop growth in DSR. Under weed-free conditions, higher crop yields (5.1 and 5.2 t ha?1 in the 2012 and 2013 seasons, respectively) were obtained at the seeding rate of 40 kg ha?1 and thereafter, yield decreased slightly beyond 40 kg seed ha?1. Under partially-weedy conditions, yield increased by 30 to 33% (2.0–2.2 and 2.9–3.2 t ha?1 in the 2012 and 2013 seasons, respectively) with increase in seeding rate from 20 to 100 kg ha?1. In the partially-weedy plots, weed biomass decreased by 41–60% and 54–56% at 35 days after sowing and at crop anthesis, respectively, when seeding rate increased from 20 to 100 kg ha?1. Results from our study suggest that increasing seeding rates in DSR can suppress weed growth and reduce grain yield losses from weed competition.
Seed Germination Ecology of Echinochloa glabrescens and Its Implication for Management in Rice (Oryza sativa L.)
Jhoana L. Ope?a, Bhagirath S. Chauhan, Aurora M. Baltazar
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092261
Abstract: Echinochloa glabrescens is a C4 grass weed that is very competitive with rice when left uncontrolled. The competitive ability of weeds is intensified in direct-seeded rice production systems. A better understanding is needed of factors affecting weed seed germination, which can be used as a component of integrated weed management in direct-seeded rice. This study was conducted to determine the effects of temperature, light, salt and osmotic stress, burial depth, crop residue, time and depth of flooding, and herbicide application on the emergence, survival, and growth of two populations [Nueva Ecija (NE) and Los Ba?os (IR)] of E. glabrescens. Seeds from both populations germinated at all temperatures. The NE population had a higher germination rate (88%) from light stimulation than did the IR population (34%). The salt concentration and osmotic potential required to inhibit 50% of germination were 313 mM and ?0.24 MPa, respectively, for the NE population and 254 mM and ?0.33 MPa, respectively, for the IR population. Emergence in the NE population was totally inhibited at 4-cm burial depth in the soil, whereas that of the IR population was inhibited at 8 cm. Compared with zero residue, the addition of 5 t ha?1 of rice residue reduced emergence in the NE and IR populations by 38% and 9%, respectively. Early flooding (within 2 days after sowing) at 2-cm depth reduced shoot growth by 50% compared with non-flooded conditions. Pretilachlor applied at 0.075 kg ai ha?1 followed by shallow flooding (2-cm depth) reduced seedling emergence by 94?96% compared with the nontreated flooded treatment. Application of postemergence herbicides at 4-leaf stage provided 85?100% control in both populations. Results suggest that integration of different strategies may enable sustainable management of this weed and of weeds with similar germination responses.
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