Effect of Nitrogen Fertilizer on Milling Quality of Rice (Oryza sativa)

The effect of nitrogen fertilizer on milling quality or milling yield of rice (Oryza sativa) was tested for two cultivars, \u27Lemont\u27 and \u27Newbonnet\u27. This was an increase in the percentage of broken kernels and a decrease in head rice yield when no nitrogen fertilizer was applied as compared to applying all of the nitrogen at preflood or in split applications. The greater affect was on Lemont, a cultivar that requires a high amount of nitrogen fertilizer for maximum grain yields. Data showed that the percentage of head rice can be reduced by as much as 7 to 22 percent in Lemont and from 2 to 6 percent in Newbonnet when no nitrogen is applied as compared to applying all of the nitrogen at preflood or in split applications. Also, these data show that the percentage of broken kernels can increase from 8 to 1 9 percent for Lemont and from 4 to 11 percent for Newbonnet when no nitrogen fertilizer is applied as compared to applying all of the nitrogen at preflood or in split applications

Influence of Thresher Cylinder Speed and Grain Moisture at Harvest on Milling Yield of Rice

The percentage of broken rice (Oryza sativa) kernels was determined after threshing the grain at varying cylinder speeds of the thresher and moisture contents of the grain at harvest. Moisture contents of the individual grain samples ranged from 12 to 26% and the two cylinder speeds were 600 and 1000 RPM. Significant differences between germplasm, cylinder speed and moisture content of the grain at harvest on milling yield was observed. For example, Newbonnet had the fewest broken kernels while Leah had the greatest amount of broken kernels. Lemont produced the highest total milling yield; whereas, L202 produced the lowest total milling yield. Newbonnet produced the highest and Leah produced the lowest head rice yield. Percentage of broken kernels approximately doubled when the cylinder speed was increased from 600 to 1000 RPM. Generally there was a significant increase in the percentage of broken kernels as the moisture content of the grain at harvest decreased

Characterization of Rice (Oryza sativa L.) Roots Versus Root Pulling Resistance as Selection Indices for Draught Tolerance

A technique described as Root Pulling Resistance (RPR) was used to evaluate genotypic differences in root growth and development of 50 rice germplasm accessions and cultivars. Several root characteristics in rice are associated with drought tolerance and avoidance capability of plants. The RPR measurements showed a significant positive correlation with maximum root length (r=0.69), root thickness (r=0.75), branching number (r=0.75), and root dry weight (r= 0.82). Rice genotypes that had a high RPR value were identified as having longer, thicker, and denser root systems. The data indicated that high RPR measurements are strongly correlated with greater root penetration. Munji Sufaid Pak, IR52 (IR5853-1 18-5) and Saunfia or Mabla Pak 329 had a significantly greater root length, root thickness, root number, root branching and dry weight as compared to IR 36. Also, there was no correlation between plant height and RPR. Furthermore, the data demonstrated that the RPR technique is ideal for selecting superior root systems and potential drought tolerant rice germplasm and cultivars

Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)

More than 50 weed species infest drill-seeded rice in the U.S. and one of the most prevalent aquatic weeks is ducksalad (Heteranthera limosa). During the summer of 1988, a field experiment was conducted to identify rice accessions from the USDA/ARS rice germplasm collection for allelopathic effects to ducksalad. In this field experiment, 5,000 accessions were evaluated for allelopathic activity. Five to seven seeds of each rice accession were planted in hills about 75cm apart in two replications. Allelopathic activity was recorded as 1) radius of the area affected by allelochemical from the base of the rice plant and 2) percentage of weed control within the affected area. Ducksalad was rated at the panicle initiation stage of rice development. Of the 5,000 accessions that were evaluated, approximately 191 were identified as having evident allelopathic activity. The accessions that demonstrated allelopathic activity originated in 26 countries (Afghanistan, Argentina, Australia, Brazil, Columbia, Dominican Republic, France, India, Iran, Iraq, Israel, Italy, Japan, Malaysia, Mexico, Pakistan, Peru, Philippines, Portugal, Republic of Korea, People Republic of China, Soviet Union, Taiwan, Thailand, Turkey, and United States)

Screening Rice (Oryza Sativa L.) Genotypes for Drought Tolerance Under Field Conditions

We evaluated the root pulling resistance (RPR) technique developed at the International Rice Research Institute (IRRI) for transplanted rice (Oryza sativa L.) to determine its applicability for assessing the drought tolerance of direct seeded rice. Experiments were conducted in 1988 and 1989 at the University of Arkansas at Pine Bluff Agricultural Research Farm. Fifty genotypes from four countries were grown with and without irrigation. The genotypes identified as drought tolerant germplasm by the RPR method in both years were significantly correlated. In both 1988 and 1 989, RPR was directly related to maximum root length, root number, and root dry weight. Root dry weight (RWT) had the highest correlation with RPR in both 1988 (r= 0.82 ** ) and 1989 (r=0.46 * * ). Cultivars with the greatest root lengths and root dry weights had the highest root pulling resistances

In vitro Culture of Several Rice Cultivars

Tissue culture methods have been established to regenerate certain rice (Oryza sativa L) cultivars, but regeneration of the rice cultivars widely grown in Arkansas has not been reported. This study has established an in vitroculture for the rice cultivars \u27Nortai\u27, \u27Starbonnet\u27, \u27Mars\u27, Tebonnet\u27, \u27Newbonnet\u27, and \u27Lemont\u27. Callus was induced in the dark at either 20 or 28 C from dehusked seeds cultured on Murashige and Skoog (MS) medium (Murashige and Skoog, 1962) containing 40 g L^-1 sucrose, 10 g L^1 agar, 0.5, 1.0, or 2.0 mg L^-1 1 2,4-dichlorophenoxyacetic acid (2,4-D) and adjusted to pH 5.7. After four weeks the calli were weighed, transferred onto MS medium containing no 2,4-D, and maintained in a 1 2-h photoperiod (65 uE m^-2 s^-1) at 25 ± 2 C to induce plant regeneration. Callus production was best when cultured on a medium containing 1.0 mg L^-1 2,4-D and incubated at 28 C. Plant regeneration was observed two to four weeks later. The percentage of calli regenerating platlets varied with the cultivar and the callus induction treatment. Callus induction at 20 C on a medium with a 2,4-D level less than 2.0 mg L^-1 enhanced the regenerability of most cultivars. Regenerates were transplanted to soil and grow normally to maturity. This system can be helpful in improving rice cultivars with tissue culture techniques such as somaclonal variant selection and somatic hybridization

Genetic and Plant Growth Regulator Manipulation of Rice (Oryza sativa L.) Mesocotyl and Coleoptile Lengths

Significant differences in mesocotyl lengths of semidwarf and non-semidwarf rice (Oryza sativa L.) cultivars were observed. However, the relationship between plant height and mesocotyl length was found to be due to linkage rather than pleiotropism. Seed treatments of gibberellic acid (GA₃) significantly increased mesocotyl and coleoptile lengths in the laboratory study. The GA₃ seed treatments significantly increased stand density compared to the untreated control in the field study. However, no significant differences were observed for plant height at maturity or grain yields among the GA₃ treatments or the untreated control

Association of Mesocotyl and Coleptile Elongation with Seeding Vigor in Rice

Three experiments were conducted to evaluate the relationship of mesocotyl and coleoptile elongation to seedling vigor and plant height in rice (Oryza sativa). A laboratory experiment was conducted to evaluate the potential lengths of the mesocotyl and coleoptile of semidwarf and standard rice genotypes. Four genotypes exhibited inherent differences in their ability for mesocotyl and coleoptile elongation. The semidwarf genotypes (\u27M-101 \u27 and RU 7703008) showed reduced mesocotyls, coleoptiles, and total lengths (mesocotyl + coleoptile); whereas, the tall plant type (\u27L-201\u27 and \u27Labelle\u27) had comparatively longer mesocotyls, coleoptiles, and total lengths. Itis assumed that mesocotyl elongation is the most important of the three parameters evaluated in seedling vigor, but total length is the least variable. Significant differences were detected among seeding depths and genotypes in the greenhouse experiment for emergence percentage, emergence index, coleoptile, and mesocotyl lengths. The field experiment verified that the low seedling vigor was due to the shorter mesocotyls and coleoptiles of the semidwarf genotypes in this test and was primarily responsible for poor stand establishment

Supernova Simulations and Strategies For the Dark Energy Survey

We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs that are passed to a cosmology fitter. We investigated several different survey strategies including field selection, supernova selection biases, and photometric redshift measurements. Using the results of this study, we chose a 30 square degree search area in the griz filter set. We forecast 1) that this survey will provide a homogeneous sample of up to 4000 Type Ia supernovae in the redshift range 0.05<z<1.2, and 2) that the increased red efficiency of the DES camera will significantly improve high-redshift color measurements. The redshift of each supernova with an identified host galaxy will be obtained from spectroscopic observations of the host. A supernova spectrum will be obtained for a subset of the sample, which will be utilized for control studies. In addition, we have investigated the use of combined photometric redshifts taking into account data from both the host and supernova. We have investigated and estimated the likely contamination from core-collapse supernovae based on photometric identification, and have found that a Type Ia supernova sample purity of up to 98% is obtainable given specific assumptions. Furthermore, we present systematic uncertainties due to sample purity, photometric calibration, dust extinction priors, filter-centroid shifts, and inter-calibration. We conclude by estimating the uncertainty on the cosmological parameters that will be measured from the DES supernova data.Comment: 46 pages, 30 figures, resubmitted to ApJ as Revision 2 (final author revision), which has subtle editorial differences compared to the published paper (ApJ, 753, 152). Note that this posting includes PDF only due to a bug in either the latex macros or the arXiv submission system. The source files are available in the DES document database: http://des-docdb.fnal.gov/cgi-bin/ShowDocument?docid=624

The Sloan Digital Sky Survey-II Supernova Survey: Search Algorithm and Follow-up Observations

The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300 sq. deg. region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, Galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the Type Ia SNe, the main driver for the Survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra. This paper describes the search algorithm and the software, and the real-time processing of the SDSS imaging data. We also present the details of the supernova candidate selection procedures and strategies for follow-up spectroscopic and imaging observations of the discovered sources.Comment: Accepted for publication in The Astronomical Journal (66 pages, 13 figures); typos correcte