The Effect of Fertilizer Use on the Variability of Barley Yields in Dry Areas

Abstract

This paper attempts to measure the effect of fertilizer use (N and P) on the variability of barley yields in dry areas. Two sets of data are utilized to measure the variability of yields. These data come from multiple site-multiple season (MS-MS) researcher-managed trials conducted mostly on farmer’s fields. The evidence quite clearly indicates that fertilizer use reduces variability in barley yields under rainfed conditions in dry areas. Furthermore, substantial gains in yields are possible along with reductions in variability. Research on this important crop of the drier regions of West Asia and North Africa (WANA) indicates that improved cultural practices, with emphasis on fertilizer use, improves the efficiency of use of the most critical limiting factor: water. Fertilizer use improves water use efficiency without increasing water use. Increased root growth and early plant establishment allow increased transpiration and reduce evaporative losses from allowing increased transpiration and reduce evaporative losses from the soil surface. Furthermore, maturity is advanced and this provides an escape mechanism from the drought stresses that invariably occur at the end of a season. These can be identified as the principal factors that reduce the variability of yields. These results are expected to influence a review of policies that restrict fertilizer allocation to dry areas as well as a review of the relative neglect of research on barley and rainfed agriculture in general at the national level.