Climate is an important environmental factor that affects on all of vital aspects. successful production completely depends on understanding of climatic condition. It is very important To know about rainfall pattern and characteristics specially in dry land farming areas which highly related to the available water. So It is very important to know about mean annual Seasonal and monthly rainfall, duration of the rainfall season and dates, probablity levels of Rainfall amounts, determinative of interval of dry and wet period, number of rainy day, land. Ultimately drought is very useful for different agricultural practices for example, prepration land for planting, fertilizing, harvesting, drying of crops and so on.
This subject helps to improve the yield and quality of agricultural products and optimum Use of the limited resources. in this study rainfall and water balance characteristics agricultural climatology point of view have been analysed. The study area is located in western of IRAN, east of kermanshah including Sahneh, Bistoon, Harsin and kermanshah plains .in this investigation, It has been used daily rainfall data in commen 26 years statistical period at meteorological station and wheat thy land farming phenological observation 8 years at Sararud station. Research finding show that, inspite of 250 mm minimum rainfall security for wheat dry land- farming, rainfall distribution and amount, water balance (as daily, different growing stages and total of growing season) the plant is exposured by water tention and moisture deficit in different growing stages and total growing season instance 75 per. In germination stage, 50 per In emergency - 75 per. In 3 leaf and 87.5 per. In tillering.
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