Effect of Optimized Nitrogen Application in Reducing Drought Stress Effect on Grain Yield of some Rainfed Bread Wheat Genotypes

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Abstract

This experiment was carried out as split split plot arrangement in randomized complete block design with three replications. Treatment included Nitrogen application time (whole fertilization of N in fall, and its split fertilization as 2/3 in fall and 1/3 in spring), Nitrogen rates (0, 30, 60 and 90 kg N ha-1) and seven bread wheat genotypes. Plant traits related to drought and nitrogen stresses were measured. Results showed that stress susceptibility index (SSI) was suitable for evaluation of relation between drought stress and N managements. According to this index, 30, 60 and 90 kgha-1 N application decreased drought stress intensity by 55, 88 and 64% compared to control, respectively. These findings were equal to an increase of 810, 1362 and 942 kgha-1 grain yield, respectively. SSI was lowest in economical optimum N rate. However, in both low and high range of N application rates drought stress effect increased compared to N economical optimum rate (ND = 0). This increase 4.5 times higher for low nitrogen application (ND 0), i.e. for every application of 10 kg N.ha-1 under economical optimum rate, SSI increased by 0.15 and grain yield of rainfed wheat decreased by 171 kgha-1. Moreover, our results showed that for obtaining higher grain yield (over 2500 kgha-1), at least 60 kg N ha-1 was required, whereas this amount should not be more than 30 kgNha-1 for low grain yields (less than 1900 kgha-1). Results of this study showed that split application of N for ND 0 may be recommended however, it seems that application time is not important where ND = 0. Mean productivity (MP) index identified Rasad, Cereal4, Azar2 and Ohadi and SSI identified Cereal2, Cereal4 and Rasad as the most tolerant bread wheat genotypes. However, Cereal2, Cereal4 and Rasad were more suitable for reduction of the effect of drought stress. Finally there was an interaction between N application and drought stress. Therefore, it can be concluded that the reduction of drought stress effect may be achieved through optimezed N application management for some rainfed wheat genotypes.

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Seed and Plant Production Journal
Volume 30, Issue 2
July 2014
Pages 169-198

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