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  • 1
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tomographic imaging of the ionosphere is a recently developed technique that uses integrated measurements and computer reconstructions to determine electron densities. The integral of electron density along vertical or oblique paths is obtained with radio transmissions from low-earth-orbiting (LEO) satellite transmitters to a chain of receivers on the earth's surface. Similar measurements along horizontal paths can be made using transmissions from Global Position System (GPS) navigation satellites to GPS receivers on LEO spacecraft. Also, the intensities of extreme ultraviolet (EUV) emissions can be measured with orbiting spectrometers. These intensities are directly related to the integral of the oxygen ion and electron densities along the instrument line of sight. Two-dimensional maps of the ionospheric plasma are produced by analyzing the combined radio and EUV data using computerized ionospheric tomography (CIT). Difficulties associated with CIT arise from the nonuniqueness of the reconstructions, owing to limited angle measurements or nonoptimal receiver location. Improvements in both reconstruction algorithms and CIT measurement systems are being implemented to overcome these difficulties. New imaging systems being developed employ CIT for large area mapping of the plasma densities in the ionosphere. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. In a long-term experiment, soil physical properties were studied after 20 annual cycles of maize-wheat-fodder cowpea cropping with annual application of inorganic fertilizers and farmyard manure (FYM). Weeds were controlled by hand or by the use of herbicides. The hand weeding treatment resulted in a lowering of the bulk density of the surface layer (0-15 cm) and a significant increase in the subsurface (15–30 cm) density. Application of FYM significantly increased the soil organic carbon (OC), infiltration rate, water retention, aggregation and aggregate stability in water. Application of inorganic fertilizers had small but statistically significant effect in increasing soil OC.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 190 (1993), S. 881-887 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Biochemistry and Biophysics 285 (1991), S. 90-96 
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 80 (1978), S. 33-38 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 109 (1982), S. 1026-1034 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 19 (1989), S. 121-126 
    ISSN: 1573-0867
    Keywords: Descriptive model ; semi-descriptive model ; soil test P ; crop removal ; long term fertilizer experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The increasing pressure on world food supplies and the recent increase in the cost of energy and fertilizers point to the need for efficient use of applied nutrients. A semi-descriptive model was developed to predict the change in extractable P with time, assuming that P added through fertilizer and amounts removed in harvested plant products were the main fluxes affecting available P status. The relationship between extractable P and the rate of P fertilization was quadratic. ‘Availability’ coefficients were evaluated from the data of a long term fertilizer experiment at Ludhiana centre. It was assumed that fixation of applied P was accommodated in these, and that practically there was no leaching and run-off of applied P in these soils. Good agreement (r = 0.99**) was found between the predicted and observed soil test P of alluvial soils of Barrackpore and New Delhi, medium black soils of Coimbatore and Jabalpur and sub-montane soil of Palampur centre. The model, however, failed to predict available P of Pantnagar and Hyderabad soils.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 225-234 
    ISSN: 1573-0867
    Keywords: long-term experiment ; maize ; wheat ; fertilizers ; farm yard manure ; weedicide application ; yield sustainability ; zinc deficiency ; nutrient uptake ; cropping sequence ; organic carbon build-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Long-term field experiments play an important role in understanding the complex interactions of plants, soils, climate and management and their effects on sustainable crop production. A long-term fertilizer experiment with maize-wheat-cowpea (fodder) is in progress since 1971 at Punjab Agricultural University farm Ludhiana, India. The experimental result for the first 21 years showed that application of N alone or in combination with P did not produce as much maize and wheat grains as the application of N, P and K together. Eight years after the start of the experiment, the optimal levels of N, P and K application (100% NPK) were unable to sustain the similar (maize) yield level as before because of Zn deficiency. Whereas in FYM amended plots the Zn deficiency did not appear and the higher crop yields could be sustained. The chemical control of weeds could not sustain the maize productivity at the same level as the manual removal of weeds. It was concluded that the high level of crop production can be sustained with the application of N, P and K under intensive cropping system provided deficiency of any of the micronutrient does not crop up. The deficiency of Zn is most likely to occur in semi-arid light textured alluvial soils under intensive cropping without the addition of farm yard manure/organic manures. In maize based cropping systems, manual control of weeds may be preferred to the chemical one. Addition of FYM in conjunction with 100% NPK is most beneficial both from bio-physical and economic point of view.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 173-177 
    ISSN: 1573-0867
    Keywords: Nitrate ; nitrogen rates ; ground water contamination ; NPK fertilizers ; apparent N recovery ; farm yard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Distribution and accumulation of NO3—N, down to 210 cm depth, in the soil profile of a long term fertilizer experiment were studied after 16 cycles of cropping (maize-wheat-fodder cowpea). The application of fertilizer N without P and K or in combination with only P resulted in higher NO3—N concentration in the soil profile than the application of N with P and K. With an annual application of 320 kg N ha−1 alone, a peak in NO3—N accumulation occurred at 135 cm soil depth. However, with the application of NPK, no peak in NO3—N distribution was discernible and its content at most of the sampling depths was either less than or equal to N and NP treatments. The annual application of 10 tons farm yard manure (FYM) per ha along with NPK resulted in a relatively lower NO3—N content in the sub soil. The amount of NO3—N accumulation in the soil profile decreased as the cumulative N uptake by the crops increased. Application of fertilizer amounts greater than that of the recommended (100% NPK) resulted in low percent N recoveries in crops and greater NO3—N accumulation in the soil profile.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 47 (1996), S. 107-114 
    ISSN: 1573-0867
    Keywords: cropping sequence ; nitrogen losses ; nitrogen uptake ; organic carbon build-up ; soil N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of N, P and K application through inorganic and organic fertilizers on N recovery in crop plants and its balance in the soil-plant (maize-wheat-cowpea fodder) was studied for the first 22 years of a long-term experiment at Punjab Agricultural University farm, Ludhiana, India. The results showed. that N removal and apparent N recovery by both maize and wheat was directly related to the balanced application of N, P and K fertilizers. Averaged over the years, application of N alone (100% N) resulted in a recovery of 17.1% in maize and 31.7% in wheat. The application of P and K along with N almost doubled (32.8% in maize and 64.7% in wheat) the apparent N recovery in the crops. Increase in soil N concentration which was related to the build-up of soil organic carbon (OC) occurred at a very slow rate with the application of N, P and K fertilizers. Addition of farm yard manure (FYM) resulted in highest N removal in crops and build-up of soil N and OC status. Application of recommended N without P and K fertilizers resulted in relatively large amounts (64–71%) of fertilizer N lost from the surface soil as compared to that (41–49%) with N, P and K applied together. Higher rate of fertilizer application (150% NPK) resulted in comparatively greater N loss (58–62%). It was concluded that balanced and judicious use of N, P and K fertilizers coupled with the addition of any deficient element (e.g. Zn) help in minimizing N losses and environmental pollution.
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