خلاصة:
Finally, prediction scenarios for the regional model and stations that had models were calculated, and the amount of wheat yield variability according to changes in climatic parameters was calculated from the normal average. The results show that the wheat crop yield in the counties of Khorasan Razavi province is variable between 200 to 534 kg per hectare in the regional model based on changes in precipitation and temperature data. Climate change has direct and indirect effects on the growth rate of agricultural crops; wheat is one of the world's strategic crops that is affected by the phenomenon of climate change. The present research was conducted in Khorasan Razavi province to study the variability of rainfed wheat yield in relation to the amount of change in climatic parameters, including temperature and precipitation, for which data from eleven meteorological stations were used. The aforementioned climatic parameters for the wheat growing period from October to June, for the statistical period from 1984 to 2003, were considered based on the availability of wheat yield data. For each station, the correlation coefficient between wheat yield and climatic parameters was calculated, and finally, a regression model for the stations was calculated to identify the climatic parameters effective in estimating wheat yield. Six stations in the region had significant regression models, and other stations in the region lacked them during the statistical period. Following the point model implementation, a regional yield model was also calculated for the province and compared with the station models. In the regional model, the parameters of total precipitation for January and February, average January temperature, average maximum January temperature, and minimum March temperature have the greatest impact on rainfed wheat yield. The obtained results show that the parameters of precipitation amount and temperature during the cold period of the year are very effective in determining the rainfed wheat yield in the region.
ملخص الجهاز:
Table 7 Statistical characteristics of the climatic parameter affecting the model and prediction scenarios at Degoz station (Refer to the page image) The average calculated yield at Degoz station is approximately 975 kg per hectare.
Table 8 Statistical characteristics of the climatic parameters affecting the model and prediction scenarios at Quchan station (Refer to the page image) **:is significant at the 0/10 level.
Table 11 Statistical characteristics of the influential climatic parameters and prediction scenarios at Torbat Jam station (Refer to the page image) According to the prediction scenarios, if the amount of the parameters of total February precipitation and minimum March temperature increases by 01 percent, the wheat yield will be equal to 86/992 kg, which shows a decrease of about 6/2 kg or 0/78 percent.
However, in other stations of the region such as Degarj, Quchan, Gonabad, Torbat Heydarieh, Kashmar, and Khorasan Razavi province, the role of climatic factors in the wheat yield has been important and effective, and the amount of change (Refer to the page image) Figure 2 Stations having correlation or lacking correlation with the regional model throughout the entire statistical period According to Figure (2), it is determined that the highest correlation between the calculated yield data of the regional model at the stations and the observed yield data of each of the studied stations, throughout the entire statistical period from 1948 to 2030, belongs to Quchan station with a value of 0.
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