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:
- Probability of chilling occurrence on bud and flower of Almond
- Probablity of rainfall greater than 250mm
- Spring and summer precipitation to annual precipitation ratio
- Probablity of occurrence of growing degree days greater than 3500 G.D.D (base temperature 0 celsius)
- Amount of available moisture index
For each of above parameters a coverage layer was prepared in GIS environment,in the second stage five mentioned coverage layers were crossed and overlapped to obtaining the agroclimatic map of area .Finally agroclimatic map reclassed to highly favorable,favorable,weak and not suitable area.
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.
Fig. (2-1): Geographical distributon of elevation in area
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.
Fig. (2-2): POAP map of Azarbaijan shargi province
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.
Fig. (2-3): Chilling occurence probability map
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:
- Probability of chilling occurrence on flowers, buds and young fruits(PCO).
- Probability of occurrence annual precipitation greater than 250mm(POAP)
- Summer and spring precipitation to annual precipitation ratio(SSPAR).
- Moisture Available Index(MAI).
- Probability of occurrence of growing season greater than 3500 degree days(POGS).
Fig. (2-4): Geographical distributon map
Tab.(2-1): List of meteorological station of area
|1||Sarab||1651||37 56||47 32|
|2||Bostanabaf||1750||37 50||46 50|
|3||Mianeh||1094||37 25||47 42|
|4||Tabriz||1361||38 05||47 16|
|5||Maragheh||1420||37 24||46 16|
|6||Sharafkhane||1302||38 11||45 29|
|7||Khodaafarin||300||38 08||46 56|
|8||Azarshahr||1400||38 26||45 45|
|9||Jolfa||704||38 57||45 38|
|10||Ahar||1300||38 29||47 03|
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.
Fig. (2-5): Geographical distributon map of FOGS
Table( 2-2): Correlation equations between studied parameters and elevation(m)
Parameter Correlation equation R2 1-PCO 1-PCO=0.0006-.0005124Z -0.644* POAP POAP=0.023+0.00043 0.624* POGS POGS=0.99001-0.00038Z -0.731* SSPAR SSPAR=0.071+0.00053Z 0.656* MAI MAI=0.0094+0.00031Z 0.699*
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.
Fig. (4-1): Agroclimatic map of Azarbaijan for Almond
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.
Table(4-1): The criteriaes determined suitability of area to Almond dryland farming
Class Parameter PCO POAP MAI SSPAR POGS Very suitable 0.80 >0.60 >0.60 >0.85 Suitable 0.25- 0.50 0.60 – 0.8 0.40 -0.60 0.40 – 0.60 0.65- 0.85 Weak 0.50- 0.75 0.40 -0.60 0.20- 0.40 0.20 – 0.40 0.45- 0.65 Not suitable >0.75