1 دانشیار گروه جغرافیای طبیعی، دانشگاه شهید بهشتی
2 کارشناس ارشد اقلیمشناسی در برنامهریزی محیطی، دانشگاه شهید بهشتی
عنوان مقاله [English]
In addition to provide oil and oil cake, implanting canola has an important effect on fixing foodstuffs and reducing soil erosion. This plant has a high compatibility with different climates and different soils and causes more in the next years of cropping. Sarpole Zahab area exceeds to 1300 km2 which 36/6% of that has the slope lower than 3°.The average of annual precipitation is 428 mm, the average of temperature is 20° cg and 20 days freezing weather in a year. The city has a suitable environmental and climate condition for implanting canola. But its implanting during the years was hopeless.
For statistical analysis and planning use from daily data of Sarpole Zahab, Eslam Abad Gharb, Ravansar and Qasre Shirin stations. Base on calculation least data necessity is 10years, because of valid and use of whole data a 15years data period was gain.
Germinate, flowering and sheath, Seeding of canola are more sensitive in growing period that use of daily data stations in the studied area and various probability we found out the time of phonology steps such as beginning dates, ending and number of each occurrence. the amount of water that plant need supplying with rain and probability of premature freezing weather in autumn and late freezing weather in spring was determined.
Use of X2 test for determinate temporary or permanent of rainfall in flowering to sheath and make to Seeding of canola growing period.
Based on scientific studies in, 20 effective environmental and climatic factors for overlapping were realized. Using climatic data of near station and by excel computing regression relationships of each element with altitude.
Planning their maps based on DEM with GIS and TIN function if was having the meaningful relationships with altitude.
Number and significance of classes was gain based on restriction and requirement of Canola.
For planning of soil temperature during germinate to Rosete the mean temperature from 5 centimeter to half meter of soil deeps and hours of 03, 09, and 15 was obtained.
For planning of premature freezing weather in autumn and late freezing weather in spring at first the dates were obtained calculate based on Julius dates then adaptations that Pierson3 have best adaptive with our data.
Results and Discussion
For determination the best area of cultivating canola in studied area with using multiple regression modeling, used from cropping data of district (kg/hec) as depended variable and environmental and climatic data effective on periods of growing as independent variable.
By using the mentioned data in multi variations regression models, some effective climatic elements in best growing and function were determined, which are: the average of soil temperature in the duration of implanting up to growing, the first freezing time in autumn, annual precipitation during growing the plant and the average of precipitation during blossoming. Based on the results the best and the most meaningful model for estimating and precipitating crop in the studied area were backward.
Based on gain equation and use from GIS and raster calculator function the layer were supplying before entrances in model and final plan was draw.
By Pierson correlation coefficient determine the correlation between amounts of estimated product by model with amounts of real product. For determinate efficacy and significance each of used variables in final model compared the significant of independent variable by beta weight.
Based on conclusion the best date for cultivating of autumn canola in studied area is the first to 15 Aban, also the growing period of canola is 170 days. Considering the daily data of rainfall shown that amount of rainfall for cultivating to germinate is less so that twice irrigation is necessary. Although the suitable rainfall were occurred in flowering to harvest time but canola damages is more severe than other growing periods that because of diffuse, showery, annual oscillation and don’t occur of 25 millimeter rainfall in same time.
Based on X2 test conclusion occur the violent oscillation of rainfall in spearing for period of flowering to sheathe and seeding. So that the oscillation of rainfall is 8 to 123 for flowering period and 11 to 113 millimeter for seeding period.
The correlation rate of cropping from canola farms in studied area with cropping that estimate by regression model is 97 percent. According to calculated amount meaningful of variables and result of other models the autumn freezing have determinant effect in site selection of suitable areas for implanting canola.
Because of not considering the slope and altitude in providing the final map, it was corrected by using Topographic map 1/50000 and field studies applying GPS.
Considering the final map, the best places for implanting Canola is plain area. Also precipitation in the studied area is not enough, so not just in the end of growing season even in the beginning of growing season irrigating is essential.