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Now showing items 281-290 of 341
Aufsatz
Effect of dressing on high-order harmonic generation in vibrating H2 molecules
(American Physical Society, 2008-04-03)
Wir entwickeln die Starkfeldnäherung für die Erzeugung hoher Harmonischer in Wasserstoffmolekülen, wobei die Vibrationsbewegung berücksichtigt wird, sowie die laserinduzierte Kopplung zwischen den beiden untersten Born-Oppenheimer-Zuständen im Molekülion, das durch die anfängliche Ionisation des Moleküls erzeugt wird. Wir zeigen, dass die Kopplung bei längeren Laserwellenlängen (≈ 2 μm) wichtig wird und zu einer Reduzierung der Erzeugung von Harmonischen führt, sowie zu einer Änderung des Verhältnisses von Harmonischen ...
Aufsatz
Verhaltensprobleme in alternativen Legehennenhaltungen
(Knierim, Ute (u.a.) (Hrsg.), 2006)
Aufsatz
Ökologische Mutterkuhhaltung in Deutschland
(Bio Austria, 2004)
Die Untersuchung bestand darin, Kenndaten zur ökologischen Mutterkuhhaltung in Deutschland zu erfassen. In einem Forschungsprojekt im Rahmen des Bundesprogramms ökologischer Landbau (Förderung durch die BLE, Bonn; vgl. HÖRNING et al. 2004) wurden Fragebögen von 388 Bio-Betrieben mit Mutterkuhhaltung ausgewertet und darüber hinaus 27 Betriebe aufgesucht zur Erhebung genauerer Daten.
Aufsatz
Mechanisms of residue mulch-induced cereal growth increases in West Africa
(2000)
The use of crop residues (CR) has been widely reported as a means of increasing crop yields across West Africa. However, little has been done to compare the magnitude and mechanisms of CR effects systematically in the different agro-ecological zones of the region. To this end, a series of field trials with millet (Pennisetum glaucum L.), sorghum [Sorghum bicolor (L.) Moench], and maize (Zea mays L.) was conducted over a 4-yr period in the Sahelian, Sudanian, and Guinean zones of West Africa. Soils ranged in pH from ...
Aufsatz
Legume rotation effects on early growth and rhizosphere microbiology of sorghum in West African soils
(2004)
Cereal yield increases in legume rotations on west African soils were the subject of much recent research aiming at the development of more productive cropping systems for the mainly subsistence-oriented agriculture in this region. However, little has been done to elucidate the possible contribution of soil microbiological factors to these rotation effects. Therefore a pot trial was conducted using legume rotation and continuous cereal soils each from one site in Burkina Faso and two sites in Togo where cropping ...
Aufsatz
Field measurements of the CO2 evolution rate under different crops during an irrigation cycle in a mountain oasis of Oman
(2004)
For millennia oasis agriculture has been the backbone of rural livelihood in the desertic Sultanate of Oman. However, little is known about the functioning of these oasis systems, in particular with respect to the C turnover. The objective was to determine the effects of crop, i.e. alfalfa, wheat and bare fallow on the CO2 evolution rate during an irrigation cycle in relation to changes in soil water content and soil temperature. The gravimetric soil water content decreased from initially 24% to approximately 16% ...
Aufsatz
Plant genetic diversity, irrigation and nutrient cycling in traditional mountain oases of northern Oman
(Li, C. J. (u.a.) (Hrsg.), 2005)
Little is known about plant biodiversity, irrigation management and nutrient fluxes as criteria to assess the sustainability of traditional irrigation agriculture in eastern Arabia. Therefore interdisciplinary studies were conducted over 4 yrs on flood-irrigated fields dominated by wheat (Triticum spp.), alfalfa (Medicago sativa L.) and date palm (Phoenix dactylifera L.) in two mountain oases of northern Oman. In both oases wheat landraces consisted of varietal mixtures comprising T. aestivum and T. durum of which ...
Aufsatz
Emmer (Triticum dicoccon Schrank) in Oman
(2004)
Emmer (Triticum dicoccon ) was collected recently in northern Oman. The material was analyzed morphologically and phenologically. It belongs to the Asiatic emmers (subsp. asiaticum) and not to the Ethiopian ones (subsp. abyssinicum), distributed in Ethiopia and Yemen, as originally expected. The determination of the material resulted in var. haussknechtianum and var. aeruginosum.
Aufsatz
Multi-site time-trend analysis of soil fertility management effects on crop production in sub-Saharan West Africa
(2002)
Soil fertility constraints to crop production have been recognized widely as a major obstacle to food security and agro-ecosystem sustainability in sub-Saharan West Africa. As such, they have led to a multitude of research projects and policy debates on how best they should be overcome. Conclusions, based on long-term multi-site experiments, are lacking with respect to a regional assessment of phosphorus and nitrogen fertilizer effects, surface mulched crop residues, and legume rotations on total dry matter of cereals ...
Aufsatz
Phosphorus placement an acid arenosols of the West African Sahel
(2003)
Phosphorus (P) deficiency is a major constraint to pearl millet (Pennisetum glaucum L.) growth on acid sandy soils of the West African Sahel. To develop cost-effective fertilization strategies for cash poor farmers, experiments with pearl millet were conducted in southwestern Niger. Treatments comprised single superphosphate hill-placed at rates of 1, 3, 5 or 7 kg P ha^−1 factorially combined with broadcast P at a rate of 13 kg ha^−1. Nitrogen was applied as calcium ammonium nitrate at rates of 30 and 45 kg ha^−1. ...