Current Issue : October - December Volume : 2011 Issue Number : 4 Articles : 5 Articles
Nine important agronomic traits were used to assess the genetic diversity of Tunisian tall fescue and to investigate the extent of genotype X environment (GE) interaction and its implications for breeding programs. These traits were studied for three consecutive years in thirty-five spontaneous populations and three cultivars. Panicle size contributed to seeds production, while the plant height at harvest and dry matter yield were selected for forage performance. Analysis of variance demonstrated that population attitude depended on the year and environmental conditions. Principal component analysis revealed significant similarities among some spontaneous populations and cultivars. The relationship between environmental conditions and agronomic traits revealed the influence of altitude, soil texture and minimum temperature on forage production, seed yield, and the architecture of plants, respectively. In addition, the local adapted ecotypes originating from Bizerte, Sidi Nsir, and Rass Rajel attained greater agronomic potentialities than control cultivars and were of considerable economic interest for the improvement of Tunisian tall fescue....
This paper presents an empirical model for classifying frozen/unfrozen soils in the entire Bras d�Henri River watershed (167?km2) near Quebec City (Quebec, Canada). It was developed to produce frozen soil maps under snow cover using RADARSAT-1 fine mode images and in situ data during three winters. Twelve RADARSAT-1 images were analyzed from fall 2003 to spring 2006 to discern the intra- and interannual variability of frozen soil characteristics. Regression models were developed for each soil group (parent material-drainage-soil type) and land cover to establish a threshold for frozen soil from the backscattering coefficients (HH polarization). Tilled fields showed higher backscattering signal (+3?dB) than the untilled fields. The overall classification accuracy was 87% for frozen soils and 94% for unfrozen soils. With respect to land use, that is, tilled versus untilled fields, an overall accuracy of 89% was obtained for the tilled fields and 92% for the untilled fields. Results show that this new mapping approach using RADARSAT-1 images can provide estimates of surface soil status (frozen/unfrozen) at the watershed scale in agricultural areas....
Experiments conducted from 2007 to 2009 evaluated germination of 11 peanut runner-type cultivars. Germination was evaluated in Petridishes incubated over a thermal gradient ranging from 14 to 30Ã?°C at 1.0?C increments. Beginning 24?hr after seeding, peanut was counted as germinated when radicles were greater than 5?mm long, with removal each day. Germination was counted daily for seven days after seeding. Growing-degree day (GDD) accumulation for each temperature increment was calculated based on daily mean temperature for that Petri dish. Two indices were obtained from a logistic growth curve used to elucidate seed germination by cultivar: (1) maximum indices of germination and (2) GDD value at 80% germination (Germ80), an indication of seed vigor the lower the Germ80 value, the greater the seed lot vigor. Based on the two indices, seed lots ââ?¬Å?AT 3081Rââ?¬Â, ââ?¬Å?AP-3ââ?¬Â, ââ?¬Å?GA-06Gââ?¬Â, and ââ?¬Å?Carverââ?¬Â had the strongest seed vigor (Germ80 26 to 47 GDD) and a high maximum incidence of germination rate (80 to 94%). Seed lots of ââ?¬Å?C99-Rââ?¬Â, ââ?¬Å?Georgia-01Rââ?¬Â, ââ?¬Å?Georgia-02Cââ?¬Â, and ââ?¬Å?Georgia-03Lââ?¬Â had inconsistent seed performance, failing to achieve 80% germination in at least two of three years....
Soil hyperspectral reflectance imagery was obtained for six tilled (soil) agricultural fields using an airborne imaging spectrometer (400ââ?¬â??2450?nm, ~10?nm resolution, 2.5?m spatial resolution). Surface soil samples (?? = 3 1 5) were analyzed for carbon content, particle size distribution, and 15 agronomically important elements (Mehlich-III extraction). When partial least squares (PLS) regression of imagery-derived reflectance spectra was used to predict analyte concentrations, 13 of the 19 analytes were predicted with ??2> 0 . 5 0, including carbon (0.65), aluminum (0.76), iron (0.75), and silt content (0.79). Comparison of 15 spectral math preprocessing treatments showed that a simple first derivative worked well for nearly all analytes. The resulting PLS factors were exported as a vector of coefficients and used to calculate predicted maps of soil properties for each field. Image smoothing with a \n3 Ã?â?? 3 low-pass filter prior to spectral data extraction improved prediction accuracy. The resulting raster maps showed variation associated with topographic factors, indicating the effect of soil redistribution and moisture regime on in-field spatial variability. High-resolution maps of soil analyte concentrations can be used to improve precision environmental management of farmlands....
The purpose of this study was to test the feasibility of applying AVIRIS sensor (Airborne Visible/InfraRed Imaging Spectrometer) for mapping and quantifying mineralogical components of three Brazilian soils, a reddish Oxisol in S�£o Jo�£o D'Alian�§a area (SJA) and a dark reddish brown Oxisol and Ultisol in Niquel�¢ndia (NIQ) counties, Goi�¡s State. The study applied the spectral index RCGb [kaolinite/(kaolinite gibbsite) ratio] and was based on spectral absorption features of these two minerals.The RCGb index was developed for the evaluation of weathering degrees of various Brazilian soils and was validated by the analysis of soil samples spectra imaged by AVIRIS and checked against laboratory mineralogical quantification (TGA:Thermal Gravimetric Analysis). Results showed to be possible mapping and quantifying the weathering degree of the studied soils and that the two selected areas presented different weathering degrees of their soils even for a same soil type....
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