Document Type : Research Paper
Authors
1
Assistant professor of Agricultural Engineering Research section, Agricultural Research Center of Semnan Province (Shahrood), Shahrood, Iran;
2
Prof.,University of Tehran, Irrigation and Reclamation Engineering Department, Karaj, Iran,
3
Prof., Ferdowsi University of Mashhad, Irrigation and Engineering Department, Mashhad, Iran;
Abstract
Crops growth and production in rainfed systems is a function of changes in climatic parameters. Identification of the effective parameters and planning for their management and/or adapting agronomic practices to those changes will result in improving production baseline and yield prediction. In order to estimate climate-yield production functions, we analyzed eight crop seasons data (1998-2006) of 25 climate parameters and rainfed wheat grain yields of four cold and semi-cold regions of Lorestan province including Aleshtar, Khoram-Abad, Aligodarz, and Boroujerd. Correlation coefficients of linear and non-linear regressions were established between each weather parameter, as the independent variable, and wheat grain yield. By path analysis method, correlation coefficients were separated into direct and indirect effects. Results showed that, in local models of production functions, the role of vapor pressure deficit during crop growth was very important. Rain water productivity of all regions determined for eight crop seasons, and the amounts of maximum, minimum, and average rain water productivity were 0.341, 0.132, and 0.234 kg per cubic meter precipitation, with the average being 20 percent lower than the national average (0.292 kg.m-3). The maximum temperature of Oct-Nov, sunshine hours,, autumn precipitation, and maximum seasonal temperature were the most sensitive parameters with respect to grain yield prediction. Determination of the effective climatic factors and the degree of their effects will help farmers in adopting improved agronomic practices (such as proper planting dates, suitable cultivars, and improving soil water holding capacity), thereby controlling the negative factors affecting criop growth and yield and improving the effectiveness of the positive factors.
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