Determining Planting Dates for Spring Safflower by Temperature and Digital Elevation Model in Esfahan Province

Introduction
Planting date plays main role in crop performance. Planting date through correspondence with
the climatic elements affect vegetative and reproductive growth and ultimately affect the quality
and quantity of crops. Among the climatic elements, temperature and day length are more
important under irrigated condition. It is necessary to mention that the majority of crops
cultivated in Iran are indifferent to day length. The temperature is the most important element in
controlling their growth period. By using long-term weather data and related software such as
Arc map we can determine the suitable planting dates for a wide area. Therefore, by eliminating
field experiment and avoiding large amount of time and cost, much can be saved. The purpose
of this study is to determine the best planting dates for spring safflower in different parts of
Esfahan province in order to gain the maximum performance in any climatic zone.
Methodology
The minimum, maximum and mean temperature of 51 synoptic and climatic stations of Esfahan
province and other neighbouring provinces from 1961 to 2011 have been used to determine the
appropriate planting dates of spring safflower in Esfahan province. Using the mean temperature
and Kriging method, Esfahan province is divided into three zones including zone 1 (warm),
zone 2 (moderate) and zone 3 (cold). For determining the planting dates of spring safflower in
different part of Esfahan province daily mean and minimum temperature from January to
October as average of 15 days have been calculated and related maps were plotted in GIS
environment. Interpolation of temperature was done by Digital Elevation Model (DEM) and
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Physical Geography Research Quarterly, 46 (3), Fall 2014 19
regression analysis between temperature and height in the GIS environment. Beginning of
planting dates in warm, moderate and cold regions were considered to reach mean of
temperature to 7, 9 and 12°C, respectively. For determining the growth inhibitory of high
temperatures, average of the 15-days mean and maximum temperature calculated from June to
September and related maps were plotted in GIS environment. The daily mean temperature of
30°C and the maximum temperature of 37°C are considered as high-temperature inhibition.
Results and Discussion
Delay in spring planting of safflower accelerates the development stages, decrease vegetative
growth and yield components, and ultimately cause safflower yield reduction. Early planting
dates due to production of higher seed yield are recommended. Thus, if the thermal
requirements of safflower provide the safflower cultivation, earlier and higher yield will be
achieved.
In the first thermal zone, information layers of the regions were combined that in them
mean temperature is reached to 7°C and the minimum temperature to above 0°C. Therefore, in
mid-January the eastern and northern half of the province is appropriate for safflower
cultivation. In this zone, in east and north parts of the province the planting dates start at
January 19 and end in March 6. Khorobiabanak and Biazehbiabanak are stations that located in
this region. In the second thermal zone, information layers of the regions were combined that in
them mean temperature reached to 9°C and the minimum temperature reached above 0°C.
Therefore, in mid-March the areas of south-eastern and central provinces were added to the
previous range. In this zone, on some parts in south of the province the planting dates start at
March 7 and end at April 4. Esfahan, Kabootarabad, Palayeshgahe Esfahan, Najafabad, and
Balan stations are located in this region. In the third thermal zone, information layers of the
regions were combined that in them mean temperature reached to 12°C and minimum
temperature reached above 0°C. Therefore, in mid-April, additional narrow strip of the northwest
to the south of the province was added to the previous range. In this zone, in the other parts
of the province the planting dates start at April 5 and end at May 21. Golpaygan, Meymeh,
Abyaneh, Daran, Singerd, Chadegan, Emam Gheys, Mehrgerd and Hamgin, Damaneh Freydan,
Freydoon Shahr, Badijan, Hana and Khonsar stations are located in this zone. It is noteworthy
that in the west and north western part of the province some regions with 2338 to 4405 m height
are not suitable for safflower planting due to low temperature.
Conclusion
Based on the results in the first, second and third thermal zones, planting dates in the province is
generally started from January and continue to May.. By considering temperature requirements
of safflower the suitable planting date must be considered. Cultivation and planting shall not
face to limited temperature and in every zone the first planting date is the best time for planting.