Agroclimatic zoning of Azarbayjan-Sharghi province for rainfed almond using GIS
Post graduate student, Teacher Training University, Tehran,Iran,
Khalili-A, Hajam-S, Kamali-G Vezvai A
Dep. of Irrigation, Agricultural faculty, Tehran University,Iran
Limitations in soil and water resources together with irregular rate of population increasing , cause that we choose a usefull landuse in our available resources.
In order to do this,climatic investigations are necessory.The objective of this study was classification of Azarbaijan Sharghi Province in aspect of climatic potential of Almond in dryland farming.For this purpose ,the precipitation and evaporation data as well as temperature paramameters of ten meteorological stations of area were collected and analysed.Following indices were selected for Almond in dryland farming:
Precision farming aims to optimize the use of natural resources. Geographical information systems (GIS) are systems for the storage, analysis and presentation of spatial data. A combination of GIS and simulation models is highly relevant for precision farming.Agroclimatic classifications have proved to be of great utility for planning and management of various agricultural and forestry activities.
Several climatic conditions may affect annual yield of deciduous fruit trees.Air temperature and rainfall are the most important climatic factors for grown and development of plant species.
The objective of present work is to use GIS, along with the model obtained, to find suitable areas for rainfed Almond.
Material and methods
Azarbaijan sharghi with 45480 Km2 area is one of the northwest provinces of Iran. Daily mean ,maximum and minimum temperature data and evapotranspiration as well as precipitation information were obtained from the synoptic and climatic stations of the area for a 25 year period(1971-1995) (Table 2-1).The phenological (flowering date) and effective rainfall data also were collected from ministry of Agriculture for the same period.
Climatic requirements of Almond
Almond (Prunus amygdalus) is one of the desicious fruits with low water requirement but very sensible flowers,buds and young fruits to chilling(Vezvai 1999).
The threshold amount of rainfall for dryland farming of Almond is annual precipitation grater than 250 mm.Not only the amount of precipitation but the distribution of it (summer and spring precipitation to annual precipitation ratio) is very important.The growing season is another factor influences the yield of almond.
The most important factor for almond planting is chilling on flowers, buds and young fruits .The threshold temperature for chilling injury is –1 degree centigrade.The above mentioned climatic parameters are the main factors that limitate almond growing specially in dryland farming.In present investigation five information layers were calculated as following:
Tab.(2-1): List of meteorological station of area
Information layers preparation in GIS
Digital elevation model(DEM)
Digital elevation model(DEM) was prepared using topographic map.For this purpose Arc/Info software and a Digitizer were used. Considering zone 38 as a base zone the digited map converted to UTM project system. By exporting the layer prepared in Arc/Info to IDRISI software the format of the map was converted from vector to raster base.DEM of area is illustrated in Fig.(2-1) .
Probability of annual precipitation greater than 250mm map
Rainfall is very important in dryland farming so we prepared a coverage for it.First of all the best statistical distribution for rainfall data was determined using HYFA software, probability of occurrence annual precipitation greater than 250mm was calculated then for each station.Regression equation between elevation and POAP was calculated(Table(2-2)).
Finally this equation was applied on DEM of area and obtained map was classified based on the following conditions (Fig.22):
Areas in which POAP is more than 0.80 is known as the firs class.
Areas in which POAP is between .60 to 0.80 is known as the second class.
Areas in which POAP is between .40 to .60 is known as the third class.
Areas in which POAP is less than 0.40 is known as the fourth class.
Table( 2-2): Correlation equations between studied parameters and elevation(m)
Probability of chilling occurrence map:
Similar to precipitation layer after fitting a good statistical distribution to minimum temperature the PCO was calculated for each station.in order to draw geographical distribution of PCO and elavation was determined for the area(table(2-2)). Existing map was classified to 4 zones(Fig(2-3)) as following:
Areas in which the PCO is less than 0.25 are known as the first class zone.
Areas in which the PCO is between 0.25 to 0.50 are known as second class.
Areas in which the PCO is between 0.50 to 0.75 are known as third class.
Areas in which the PCO is more than 0.75 are known as fourth class.
Geographical distribution of MAI
Moisture available index(MAI) is one of the most important factors in dryland farming.MAI obtained by effective rainfall devided by evapotaranspiration according to:
MAI = Pe/ETC
Where Pe is the sum of effective rainfall and ETC is total crop (Almond) evapotranspiration in the growing season.
Geographical distribution of MAI was obtained in same approach as PCO.Four distingushed areas can be recognized from MAI map(Fig(2-4)) as following:
Areas in which MAI was more than 0.60 are known as the first class.
Areas in which MAI was between 0.40 to 0.60 are known as the second class.
Areas in which MAI was between 0.20 to 0.40 are known as the third class.
Areas in which MAI was less than 0.20 are known as the fourth class.
Geographical distribution map of POGS:
Geographical distribution of POGS(fig2-5) determined in same method as previous elements.Distinguished areas can be ranked as following:
Areas in which POGS was between 0.65- 0.85 are known as the first class.
Areas in which POGS was between 0.65 to 0.85 are known as the second class.
Areas in which POGS was between 0.45 to 0.65 are known as the third class.
Areas in which POGS was less than 0.45 are known as the first class.
Geographical distribution map of SSPAR:
Althought the amount of annual precipitation is a main factor in dryland farming but its distribution during the year is very important too, in order to draw geographical distribution of SSPAR regression equation between elevation and SSPAR was determined(table( 2-2) and applied to DEM.Major classified zones are as following (Fig(2-6)):
Areas in which SSPAR was more than 0.65 are known as the first class.
Areas in which SSPAR was between 0.45 to 0.65 are known as the second class.
Areas in which SSPAR was between 0.25 to 0.45 are known as the second class.
Areas in which SSPAR was less than 0.25 are known as the second class.
To producing the Agroclimatic map of Azarbaijan province for Almond dryland farming the 5 above mentioned maps(PCO,POAP,MAI,SSPAR and POGS maps) were overlaid and crossed.resultant map can be classified to four distinguished zones as following (refer to table( 4-1) and fig(4-1)):
Very suitable zones(first class)
There is a high corresponance between climatic conditions of area and the climatic requirement of Almond in this zone.The areaofth is zone is about 4852.9 km2 ndincludes: Hurand, Kalaleh and Ghareaghaj regions.
Suitable areas(second class)
Although there is aweaker correspondence between climatic conditions and requirements of Almond in these areas compare to first zone it is possible to make condition better with supplemental irrigation and other Agricultural activities(such as planting tolerant specious to drought and chilling).The area this zone is about 2833 km2 and includes:Azarshahr,Maraghe,bostanabad,Sarab,Zenuz and Varzaghan.
Weak areas(third class)
These areas have low potential and low yield for dryland farming of Almond ,The area of this zone is about 10052 km2 and includes malekan,sharafkhane,kalibar,Bonab,Marand and Tabriz regions.
Not suitable areas (fourth class)
This zone consider as areas that are not suitable for Almond dryland farming because of a non-corresponding between climatic conditions and requirement of Almond.The most important factor that limits planting of Almond in these areas is chilling injury on flowers ,buds and young fruits .Area of this zone is about 2242.1 km2 and includes:Tasuj,Khomarloo,and Haris regions.
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