In order to quantify the virtual water part which is contained in the imported cereals, compared with the hydraulic potentialities which are annually mobilised through the national territory, and on the basis of the a...In order to quantify the virtual water part which is contained in the imported cereals, compared with the hydraulic potentialities which are annually mobilised through the national territory, and on the basis of the agricultural statistics, we have determined the average quantities of the imported cereals per year in order to determine the virtual water volume that these cereals bind. The water needs of the cereals which are produced in Algeria have been calculated by the Cropwat software, in order to define the equivalent quantities of water in their production on the national scale. The obtained results confirm the importance of the annually imported virtual water, through the imported cereals, comparing with the national hydraulic potentialities. Our study shows also that in spite of the strategic importance of the virtual water in the imported cereals, a diminution has to take place, on the average term, by an improvement of the use efficiency of the precipitations （green virtual water） using the best mastery of the technical itinerary in general, and also the efficient use of precipitations in particular.展开更多
When precision fanning management zones （MZs） are delineated in an agricultural field for precision nutrient management, unsupervised classification and cluster analysis procedures using remote sensing image analysi...When precision fanning management zones （MZs） are delineated in an agricultural field for precision nutrient management, unsupervised classification and cluster analysis procedures using remote sensing image analysis software are performed. These unsupervised classification and cluster analysis procedures are performed on the basis of the assumption that grouping of data points into naturally occurring clusters reduces within zone variability. The problem is that, there are small patches of different soil types within each management zone that are regarded as insignificant by the farmer, and are assimilated within larger MZs. These will consequently make soils within a management zone to be inhomogeneous. The objective of this study was to determine the probability of soil sampling occurrences on patches assimilated during delineation of MZs after a cluster analysis was performed. The study was conducted on a 5.0 ha （25°05′34.46″ S and 28°18′30.01″ E） and a 24.4 ha （23°59′04.61″ S and 28°52′29.43″ E） fields in the Waterberg District of the Limpopo Province in South Africa. A bare-soil high resolution Quickbird satellite imagery of a conventionally tilled agricultural field was used to develop MZs in the field. Soils were sampled using systematic unaligned sampling on a 35.0 m and 30.0 m grids for the 24.4 ha and 5.0 ha fields, respectively. Probabilities were calculated based on percentage area assimilated during the cluster analysis procedure that was performed using remote sensing image analysis software. The results indicated that in the 24.4 ha field there were 2.5 ha patches of high and medium zones that were assimilated within the low zone, and thus making low zones non-homogeneous. After cluster analysis and assimilation of patches, the low zone in the 24.4 ha field increased by 45.5% （2.5 ha） while the high zone was 16.4% （2.4 ha） smaller in size. In the smaller field of 5.0 ha, the high zone, which was originally 3.20 ha, lost 0.37 ha （11.6%）, which was assimilated in either low or medium zone. The study indicates that unequal probability proportional to size sampling could be used to minimize error when sampling across precision farming MZs because typically the low, medium and high MZs are not of equal size and do not contribute equally towards the mean values of soil samples.展开更多
The phenomenon of disproportional expansion of urbanized areas into undeveloped area or ＂urban sprawl＂ has become a very a remarkable characteristic of urban development worldwide in the last decades. Urban sprawl i...The phenomenon of disproportional expansion of urbanized areas into undeveloped area or ＂urban sprawl＂ has become a very a remarkable characteristic of urban development worldwide in the last decades. Urban sprawl is the popular media as the source of numerous social, environmental, and economic ills. One of the most evident consequences of urban sprawl is destroying agricultural lands around cities. One of the extreme expanded cities in Iran is Tehran megalopolis and cities around it. Tehran is expanding in all dimensions especially toward western side where Karaj city is located. The area of study for this research is Tehran and Karaj cities where the event of urban sprawl is happening. Materials used for achieving goal are aerial photographs, satellite images, thematic map of degree of soil and GIS software. The result of analysis shows that Tehran area has expanded from 10000 in 1956 to 80835 hectares in 2006. Area of Karaj city increased from 125 to 26000 hectare in the same period and the population density of two cities together decreased from 116 to 43 people per hectare. Sixty five percent of areas of these two cities are consisted of good fertile agricultural lands with irrigation potential. Twenty four percent of this land （14900 hectares） is classified as rank or class 1, 38.1 percent （23725 hectares） has rank 2, and 37.9 percent （23605） has rank 3 in terms of fertile land. Based on soil class and potential of production of wheat, it is estimated that if urban sprawl and expansion of these cities decreased or the direction of expansion changed to unfertile lands （class 4, 5 and 6）, and the cultivation of land had continued, 270,000,000 kilos of wheat could be produced yearly. So, urban sprawl is seen as one of the potential challenge to urban sustainable development and cannot be urban sustainable form.展开更多
文摘In order to quantify the virtual water part which is contained in the imported cereals, compared with the hydraulic potentialities which are annually mobilised through the national territory, and on the basis of the agricultural statistics, we have determined the average quantities of the imported cereals per year in order to determine the virtual water volume that these cereals bind. The water needs of the cereals which are produced in Algeria have been calculated by the Cropwat software, in order to define the equivalent quantities of water in their production on the national scale. The obtained results confirm the importance of the annually imported virtual water, through the imported cereals, comparing with the national hydraulic potentialities. Our study shows also that in spite of the strategic importance of the virtual water in the imported cereals, a diminution has to take place, on the average term, by an improvement of the use efficiency of the precipitations （green virtual water） using the best mastery of the technical itinerary in general, and also the efficient use of precipitations in particular.
文摘When precision fanning management zones （MZs） are delineated in an agricultural field for precision nutrient management, unsupervised classification and cluster analysis procedures using remote sensing image analysis software are performed. These unsupervised classification and cluster analysis procedures are performed on the basis of the assumption that grouping of data points into naturally occurring clusters reduces within zone variability. The problem is that, there are small patches of different soil types within each management zone that are regarded as insignificant by the farmer, and are assimilated within larger MZs. These will consequently make soils within a management zone to be inhomogeneous. The objective of this study was to determine the probability of soil sampling occurrences on patches assimilated during delineation of MZs after a cluster analysis was performed. The study was conducted on a 5.0 ha （25°05′34.46″ S and 28°18′30.01″ E） and a 24.4 ha （23°59′04.61″ S and 28°52′29.43″ E） fields in the Waterberg District of the Limpopo Province in South Africa. A bare-soil high resolution Quickbird satellite imagery of a conventionally tilled agricultural field was used to develop MZs in the field. Soils were sampled using systematic unaligned sampling on a 35.0 m and 30.0 m grids for the 24.4 ha and 5.0 ha fields, respectively. Probabilities were calculated based on percentage area assimilated during the cluster analysis procedure that was performed using remote sensing image analysis software. The results indicated that in the 24.4 ha field there were 2.5 ha patches of high and medium zones that were assimilated within the low zone, and thus making low zones non-homogeneous. After cluster analysis and assimilation of patches, the low zone in the 24.4 ha field increased by 45.5% （2.5 ha） while the high zone was 16.4% （2.4 ha） smaller in size. In the smaller field of 5.0 ha, the high zone, which was originally 3.20 ha, lost 0.37 ha （11.6%）, which was assimilated in either low or medium zone. The study indicates that unequal probability proportional to size sampling could be used to minimize error when sampling across precision farming MZs because typically the low, medium and high MZs are not of equal size and do not contribute equally towards the mean values of soil samples.
文摘The phenomenon of disproportional expansion of urbanized areas into undeveloped area or ＂urban sprawl＂ has become a very a remarkable characteristic of urban development worldwide in the last decades. Urban sprawl is the popular media as the source of numerous social, environmental, and economic ills. One of the most evident consequences of urban sprawl is destroying agricultural lands around cities. One of the extreme expanded cities in Iran is Tehran megalopolis and cities around it. Tehran is expanding in all dimensions especially toward western side where Karaj city is located. The area of study for this research is Tehran and Karaj cities where the event of urban sprawl is happening. Materials used for achieving goal are aerial photographs, satellite images, thematic map of degree of soil and GIS software. The result of analysis shows that Tehran area has expanded from 10000 in 1956 to 80835 hectares in 2006. Area of Karaj city increased from 125 to 26000 hectare in the same period and the population density of two cities together decreased from 116 to 43 people per hectare. Sixty five percent of areas of these two cities are consisted of good fertile agricultural lands with irrigation potential. Twenty four percent of this land （14900 hectares） is classified as rank or class 1, 38.1 percent （23725 hectares） has rank 2, and 37.9 percent （23605） has rank 3 in terms of fertile land. Based on soil class and potential of production of wheat, it is estimated that if urban sprawl and expansion of these cities decreased or the direction of expansion changed to unfertile lands （class 4, 5 and 6）, and the cultivation of land had continued, 270,000,000 kilos of wheat could be produced yearly. So, urban sprawl is seen as one of the potential challenge to urban sustainable development and cannot be urban sustainable form.
