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Haïfa University (2014)

The impact of agricultural practices on soil loss by aeolian erosion in the semi-arid loess of the northern-Negev

Smadar Tanner

Titre : The impact of agricultural practices on soil loss by aeolian erosion in the semi-arid loess of the northern-Negev

השפעת ממשקים חקלאיים על אובדן קרקע לס בסחיפה איאולית בצפון מערב הנגב / סמדר טנר ; בהנחיית : אברהם חיים, יצחק קטרה.

Auteur : Smadar Tanner

Etablissement de soutenance : Haïfa University

Grade : Master 2014

Résumé
Thousands acres of loess soil is being cultivated for agricultural uses in the Northern-Negev (Israel). After harvesting the winter crops, most soils remain bare and dry during the summer and therefore are exposed to wind erosion (aeolian erosion). Agricultural practices affect topsoil properties and thus the sensitivity of the soils to aeolian erosion. Winter cereals – summer fallow crop rotation is one of the most common crop rotation in the agricultural loess soil of the Northern-Negev and other soils in the world. The study examine the differences in soil quality and stability against wind erosion following crop rotation in two agricultural practices (Conventional, Organic) by in-situ aeolian experiments (using a portable wind tunnel) and analysis of topsoil properties. The effect of soil treatment, applied after harvest in each agricultural practice, was examined : mechanical tillage (chisel, discus) in conventional agriculture and stubble grazing of two intensities (over grazing, medium grazing) in organic agriculture. In each agricultural practice, control plots (with no soil treatment) were defined. The study focuses on a quantitative assessment of the short-term effect of the above treatments. The results show that the soil treatments in each agricultural practice affected differently the top soil properties. Mechanical tillage and stubble grazing had a direct effect on soil aggregation measured as MWD (Mean Weight Diameter). SOM (Soil Organic Matter), CaCO3 which are known as important cementing material of the soil, and MWD, were higher in the Organic agricultural soil although soil strength parameter was higher in the Conventional agriculture soil. The results of the aeolian experiments revealed higher soil loss (through both aeolain parameters TAS [Total Aeolian Sediments] and PM10 [Particulate Matter < 10 µm in diameter]) under mechanical tillage and stubble grazing treatments compare to the control plots. In the Conventional practice higher soil loss was measured under discus than under chisel. In the Organic practice soil loss was higher as the grazing intensity increased. No difference in the soil loss rate was found compering the control plots of each agricultural practice. Statistical analysis showed that the MWD (a common soil stability index) does not provide a significant measure for soil loss measure in the specific soil condition of this research. The finding demonstrates quantitatively the impact of agricultural practice\soil treatment on the soil loss by wind in the short-term. Annual soil loss by wind erosion can be decrease by applying the following practices : Reduced tillage (chisel instead of discus) or No-till practice, controlled stubble grazing, and by reducing the time period of cultivated bare dry soil after winter harvest.

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