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Soil water evaporation, redistribution of surface applied salts and unsaturated hydraulic conductivity were determined in field plots of a silt loam soil kept either untilled or tilled to a depth of 5 cm 2–3 days following irrigation. The hydraulic gradients measured were comparatively steeper and the zone of zero flux during drying occurred at greater depths in untilled than tilled soil. Tillage induced soil mulch reduced evaporation losses; its effectiveness, however, decreased during high external evaporative demand conditions. Some empirical relations to determine evaporation utilizing more easily accesible parameters, such as surface soil water content or suction and U.S. open-pan evaporation, were established for predictive purposes. Due to reduction in upward movement of water, shallow tillage resulted in decrease in upward movement of salts and thus, increased the efficiency of leaching during intermittent ponding. The empirical relationship describing the leaching process showed a net saving of 12.7% in water required to attain 70% removal of surface accumulated salts. Increase in unsaturated hydraulic conductivity of soil due to salinization was also observed. 相似文献
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Pankaj Sharma Inderjit Singh Asmita Sirari Gaurav Khosla Gurjeet Singh Navkiran Kaur Ludhar Sarvjeet Singh 《Plant Breeding》2019,138(6):741-747
Inheritance of fertility restorer gene in pigeonpea was studied using F2 and BC1F1 populations derived from cross AL103A × IC245273. It was found to be controlled by single dominant gene. Out of 228 SSR primer pairs, 33 primer pairs showed parental polymorphism, while four primers were found polymorphic in bulk segregant analysis (BSA). These four primers viz., CcM 1615, CcM 0710, CcM 0765 and CcM 1522 were used for genotyping of F2 population and were found to be placed at 3.1, 5.1, 28.1 and 45.8 cM, respectively. Two of them, CcM 1615 and CcM 0710, evinced clear and unambiguous bands for fertility restoration in F2 population. The Rf gene was mapped on linkage group 6 between the SSR markers CcM 1615 and CcM 0710 with the distances of 3.1 and 5.1 cM, respectively. The accuracy of the CcM 1615 was validated in 18 restorers and six maintainer lines. The marker CcM 1615 amplified in majority of male restorer lines with a selection accuracy of 91.66%. 相似文献
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Active remote sensing and grain yield in irrigated maize 总被引:2,自引:0,他引:2
Advances in agricultural technology have led to the development of active remote sensing equipment that can potentially optimize N fertilizer inputs. The objective of this study was to evaluate a hand-held active remote sensing instrument to estimate yield potential in irrigated maize. This study was done over two consecutive years on two irrigated maize fields in eastern Colorado. At the six- to eight-leaf crop growth stage, the GreenSeeker? active remote sensing unit was used to measure red and NIR reflectance of the crop canopy. Soil samples were taken before side-dressing from the plots at the time of sensing to determine nitrate concentration. Normalized difference vegetation index (NDVI) was calculated from the reflectance data and then divided by the number of days from planting to sensing, where growing degrees were greater than zero. An NDVI-ratio was calculated as the ratio of the reflectance of an area of interest to that of an N-rich portion of the field. Regression analysis was used to model grain yield. Grain yields ranged from 5 to 24 Mg ha?1. The coefficient of determination ranged from 0.10 to 0.76. The data for both fields in year 1 were modeled and cross-validated using data from both fields for year 2. The coefficient of determination of the best fitting model for year 1 was 0.54. The NDVI-ratio had a significant relationship with observed grain yield (r 2 = 0.65). This study shows that the GreenSeeker? active sensor has the potential to estimate grain yield in irrigated maize; however, improvements need to be made. 相似文献
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Khosla V 《Science (New York, N.Y.)》2008,322(5900):371-4; author reply 371-4
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In-season nitrogen (N) management of irrigated maize (Zea mays L.) requires frequent acquisition of plant N status estimates to timely assess the onset of crop N deficiency and its spatial
variability within a field. This study compared ground-based Exotech nadir-view sensor data and QuickBird satellite multi-spectral
data to evaluate several green waveband vegetation indices to assess the N status of irrigated maize. It also sought to determine
if QuickBird multi-spectral imagery could be used to develop plant N status maps as accurately as those produced by ground-based
sensor systems. The green normalized difference vegetation index normalized to a reference area (NGNDVI) clustered the data
for three clear-day data acquisitions between QuickBird and Exotech data producing slopes and intercepts statistically not
different from 1 and 0, respectively, for the individual days as well as for the combined data. Comparisons of NGNDVI and
the N Sufficiency Index produced good correlation coefficients that ranged from 0.91 to 0.95 for the V12 and V15 maize growth
stages and their combined data. Nitrogen sufficiency maps based on the NGNDVI to indicate N sufficient (≥0.96) or N deficient
(<0.96) maize were similar for the two sensor systems. A quantitative assessment of these N sufficiency maps for the V10–V15
crop growth stages ranged from 79 to 83% similarity based on areal agreement and moderate to substantial agreement based on
the kappa statistics. Results from our study indicate that QuickBird satellite multi-spectral data can be used to assess irrigated
maize N status at the V12 and later growth stages and its variability within a field for in-season N management. The NGNDVI
compensated for large off-nadir and changing target azimuth view angles associated with frequent QuickBird acquisitions. 相似文献
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Budget of nutrient in plant and soil, and their rates of recycling in three types of traditional agroforestry systems in mid
elevations of the western Himalaya were studied. Concentration of nitrogen and potassium was significantly higher in fruits
and leaves than in branches, boles, and litter. Grewia optiva, an important fodder tree, was found to be rich in potassium, vegetable crops in nitrogen, and weeds in phosphorus. Maximum
store of nutrients was estimated in aboveground biomass of agrihortisilvicultural system: nitrogen 532, phosphorus 40, potassium
461, calcium 400, and magnesium 298 kg/ha; it was closely followed by that in agrihorticultural system, and both these had
sbout 2-fold higher nutrient stock as compared to agrisilvicultural system. In the case of the former two systems, considerable
quantity of nutrients up to nitrogen 169, phosphorus 14, potassium 165, calcium 97, and magnesium 65 kg/ha, for example in
agrihortisilvicultural system, was recycled through debris of crops and weeds, and tree leaf litter, while the recycling rate
was almost half in agrisilvicultural system. Through ‘harvest’ potassium was depleted in the largest quantity from the system,
followed by nitrogen, magnesium, calcium, and phosphorus; much higher loss occurred through agricultural and/or horticultural
edible parts as compared to fuel and fodder biomass. For example, the loss through agricultural crops and horticultural fruits
for nitrogen in agrihortisilvicultural system was up to 75 percent and 38 percent respectively of the total annual uptake.
This heavy loss makes the system unstable from a nutrient point of view particularly for nitrogen and potassium until external
inputs are added through organic and inorganic fertilizers. Agrihortisilvicultural system is remarkably efficient in view
of biomass productivity for fuel, fodder and fruits, and also from nutrient point of view provided losses through harvest
are compensated externally. 相似文献
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E. G. Souza C. L. Bazzi R. Khosla M. A. Uribe-Opazo Robin M. Reich 《Journal of plant nutrition》2016,39(4):531-538
Technological advances in precision agriculture in the last two decades have made yield monitoring and mapping an economically feasible option or practice for farmers. Differentially corrected Global Positioning System (GPS)-equipped yield monitoring system on a combine allows collection of georeferenced yield data which when coupled with a geographic information system (GIS) can generate yield maps via several interpolation techniques. Scientists and practitioners have reported to use multiple different types of interpolation techniques to process yield data. However, one of the aspects that still need to be elucidated is the influence of the different interpolation methods on the quality of the resulting thematic yield maps. The objective of this study was to investigate the influence of three interpolation methods (i.e., inverse of distance, inverse of square distance, and ordinary kriging) commonly used in developing yield maps. An index for the comparison of errors (ICE) was proposed to provide an objective criterion for selecting an experimental variogram model to use with the kriging. Results indicate that inverse distance squared performed slightly better in predicting yields than either inverse distance or ordinary kriging. With a mean absolute difference varying from 0.04 to 0.32 t ha?1 corresponding to a relative deviation from 1.20 to 7.53%, the management decisions can differ in some cases based on the type of interpolation implemented. 相似文献
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Structural basis for gluten intolerance in celiac sprue 总被引:1,自引:0,他引:1
Shan L Molberg Ø Parrot I Hausch F Filiz F Gray GM Sollid LM Khosla C 《Science (New York, N.Y.)》2002,297(5590):2275-2279
Celiac Sprue, a widely prevalent autoimmune disease of the small intestine, is induced in genetically susceptible individuals by exposure to dietary gluten. A 33-mer peptide was identified that has several characteristics suggesting it is the primary initiator of the inflammatory response to gluten in Celiac Sprue patients. In vitro and in vivo studies in rats and humans demonstrated that it is stable toward breakdown by all gastric, pancreatic, and intestinal brush-border membrane proteases. The peptide reacted with tissue transglutaminase, the major autoantigen in Celiac Sprue, with substantially greater selectivity than known natural substrates of this extracellular enzyme. It was a potent inducer of gut-derived human T cell lines from 14 of 14 Celiac Sprue patients. Homologs of this peptide were found in all food grains that are toxic to Celiac Sprue patients but are absent from all nontoxic food grains. The peptide could be detoxified in in vitro and in vivo assays by exposure to a bacterial prolyl endopeptidase, suggesting a strategy for oral peptidase supplement therapy for Celiac Sprue. 相似文献