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Accueil du site → Doctorat → Allemagne → 2016 → Water use efficiency and management of agro-pastoral landuse systems in the Mongolian-Chinese Altay

University of Kassel (2016)

Water use efficiency and management of agro-pastoral landuse systems in the Mongolian-Chinese Altay

Jordan, Greta

Titre : Water use efficiency and management of agro-pastoral landuse systems in the Mongolian-Chinese Altay

Auteur : Jordan, Greta

Université de soutenance : University of Kassel

Grade : Doktor der Agrarwissenschaften (Dr. agr.) 2016

Résumé
The use of organic fertilizers is an important approach to maintain soil fertility of irrigated agricultural land under the semi-arid climate conditions of Oman. However, gaseous emissions of carbon and nutrients from soil and organic fertilizers are a major challenge. Activated charcoal and tannins have the potential to reduce gaseous losses of carbon and nitrogen. Therefore, gaseous emissions of carbon dioxide (CO2), ammonia (NH3) and nitrous oxide (N2O) were measured by a photo-acoustic infrared multi-gas monitor. These gaseous losses were determined from compost and soil amended with goat manure and additionally mixed with either activated charcoal, tannin or the sum of these both additives. Results showed that peaks of gaseous carbon and nitrogen emission were reduced and/or temporally shifted after tannin applications to compost as well as soil. Tannins applied directly to soil reduced N2O (-17%) and in particular NH3 (-51%) emissions in comparison with the control. Based on these results, tannins appear to be a promising amendment to composts and soils to mitigate gaseous emissions, especially under semi-arid climate conditions. Transhumance systems in the Altay-Dzungarian region of China and Mongolia are characterized by mixed herds on seasonal grazing sites in the desert, mountain steppe and alpine belt. Spatio-temporal mobility patterns of pastoral herds, number and size of utilized pastures, and the herbage offer and its nutritive value were investigated. To this end, one representative goat and cattle was equipped with a GPS collar and biomass was determined at 869 sampling locations. allowance (kg dry matter per sheep unit-1 day-1) ranged in average from 34/17 to 91/95 (China/Mongolia) at the onset of a grazing period, whereby only Chinese spring pastures showed lower values. It can be concluded that official regulations in combination with higher amounts of spring rainfall seem to generate higher herbage yields on the Chinese site. In Mongolia, increased goat numbers and reduced livestock mobility in combination with low precipitation affect herbage allowance. Increasing the animals’ daily grazing radius by active herding may reduce grazing pressure and improve pasture productivity. Land cover and land use changes are likely to decrease the water availability of river oases in Mongolia. Therefore, a study was conducted to analyze land cover changes between 1972 and 2013 as well as the current prevailing farming practices of a river oasis in Western Mongolia. Additionally, the water-use efficiency was simulated by using the Soil and Water Assessment Tool (SWAT). The comparison of two satellite images indicated a change from natural rangeland to built-up areas and river water receiving sites. Overall, an area of 769 ha received irrigation water drawn from the Bulgan River. Modelled auto-irrigation as well as auto-irrigation and fertilization management increased the yield by about 46 and 77%, respectively. The water use efficiency of biomass ranged from 11 to 52 kg ha-1 mm-1 for rangeland and wetland. High evapotranspiration/precipitation ratio values and the potential rise of evapotranspiration, especially due to land cover changes, underlined the importance of a more efficient use of water in the Bulgan sum watershed. Under these conditions biomass productivity per unit water transpired and evaporated need to be improved by adapted irrigation practices and management practices.

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Page publiée le 17 janvier 2019