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Showing 2 results for Effective Rain

M Mahbod, Alireza Sepaskhah, Marzih Monfared,
Volume 13, Issue 49 (10-2009)
Abstract

Optimum management of water use in agriculture results in higher cultivated areas or enhances the share of water for municipal and industrial uses leading to economic development of a country. One of the effective methods in optimum water management is irrigation scheduling by using models which simulate water content in soils. In this study, a previously prepared model for irrigation water scheduling was modified to calculate daily effective rain, soil water content and deficiency. The model was applied for winter wheat field in Bajgah area using 13 years of local meteorological data. Furthermore, the effect of water storage in the soil profile on the amount and frequency of irrigation was examined. This model was written in Visual Basic.Net programming software. The model was run under two assumptions: 1) the effective rain compensates water deficiency of soil down to daily root depth and the excess water is assumed as deep percolation (case I) 2) the effective rain compensates water deficiency of soil down to maximum root depth and the excess water is assumed as deep percolation (case II). The results show that the amount and the frequency of irrigation in case 2 is less than case 1. Average amount and number of irrigation events decreased from 706.8 (mm) and 8 in case I to 569.2 and 6.4 in case II. The average relative percentage of effective rain increased from 45.2 % in case I to 76.9% in case II. The effective rain is 108.9 mm and the amount and number of irrigation events is 9 and 757.7 mm, respectively in case I (at probability level of 80%). The effective rain is 236.7 mm and the amount and number of irrigation events is 636.9 mm and 7.2, respectively in case II (at probability level of 50%). The effective rain is 165.6 mm and the amount and number of irrigation events is 712.6 mm 8, respectively in case I. The effective rain is 292.1 mm and the amount and number of irrigation events is 545.1 and 6, respectively in case II.
Dr. S. Akhavan, N. Delavar, Dr. A. M. Mehnatkesh,
Volume 21, Issue 2 (8-2017)
Abstract

The aim of this study was to investigate the climate change impacts on some factors affecting rainfed wheat growth such as effective rainfall, planting date and length of growing season in four stations located in Chaharmahal and Bakhtiari province. Firstly, it is necessary to predict future (2046-2065) climatic conditions. For this purpose, the output of HADCM3 general circulation model was used under three scenarios of A1B, A2 and B1. The data were downscaled by LARS-WG model. After simulating the climatic parameters in mention period, the effective rainfall during the wheat growing season was calculated by Food and Agriculture Organization method. Also, the optimum planting date was defined according to the date of the first rain (at least 10 mm in case of continuing for next days). The wheat's growth stages were determined by Growing Degree Days method. The results indicated a rise in temperature for four stations. On average, it is expected that the annual temperature increase by 1.8°C compared with the baseline period (2010-1990). Total annual precipitation in Shahrekord, Koohrang and Borujen will decrease 2.2, 7.8 and 3.6 per cent respectively. About Lordegan it will increase by 2.7 per cent. Also, the results showed that in three stations of Shahrekord, Koohrang and Borujen, the amount of effective rainfall in November will increase compared to baseline, but in Lordegan it will reduce. So, in the first three stations, in most years, planting date was obtained earlier than baseline, but in Lordegan it was later than baseline. The Length of growing season will reduce in Shahrekord, Borujen and Lordegan stations, 12 days on average and in Koohrang about 13 days.


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