Interaction effects of different irrigation levels and water salinity on growth, yield and yield components of wheat (Triticum aestivum L.) in Birjand region

Due to the presence of Iran in the arid and semi-arid regions of the world, drought and salinity are environmental stresses known as main factors that led to reduce the production of crops in Iran. Drought and salinity are major abiotic stresses that adversely affect crop productivity and quality. Their harmful effects are increasing due to global warming, and human activities such as overutilization of water resources, over-irrigation, and improper drainage, besides natural causes such as high evaporation rates in arid and semi-arid regions that led to decrease available water and increase salt accumulation in this sites. Drought and salinity have osmotic, ionic and nutritional constraint effects on plants. These effects lead to disturb photosynthetic path, growth retardation, metabolic disturbances and oxidative stress. Usually, these stresses happened at the same time especially in arid and semi-arid regions. Therefore, this study was conducted for determination growth and yield response of wheat to drought and salinity happened at the same time.

In order to evaluate the response of unfarm 4 wheat cultivar to different irrigation water and salinity levels, a factorial experiment based on a completely randomized block design with three replications was conducted at research field of agriculture, University of Birjand in 2016-2017. The treatments consisted of different levels of irrigation (I1, I2, I3 and I4, respectively 125, 100, 75 and 50% of plant water requirement and I5 including rain fed with one supplementary irrigation) and two levels of irrigation water salinity (non-saline (S1=1.4 dS.m-1) and Saline (S2= 5.4 dS.m-1) water, respectively). The studied traits included plant height, leaf area, spike length, 1000-seed weight, plant fresh weight, plant dry weight, number of seeds per spike, spike length, biological yield, grain yield, and harvest index.

The results of analysis of variance showed that the significant effect of different levels of irrigation at 0.1% level on all traits including plant height, leaf area, 1000-seed weight, fresh weight of plant, plant dry weight, spike length, number of seeds per spike , biological yield, economic performance and harvest index are (Table 3). In agreement with results of this study Wajid et al., (2002) reported that improvement of wheat yield with increasing irrigation levels. Plant height, 1000-seed weight, grain yield, and harvest index of wheat (Varamin cultivar) were significantly affected by irrigation levels (Eidizadeh et al., 2016). Soleimani (2016) also reported that the yield and yield components of wheat (in the climate of Isfahan) were strongly influenced by different levels of irrigation. The effect of irrigation water salinity was significant at 1% on plant height, leaf area and 1000-seed weight, but its effect on fresh weight of plant, plant dry weight, spike length, number of seeds per spike, biological yield, economic yield, and harvest index was not significant (Table 3). Irrigation water salinity on yield and yield components of different wheat cultivars including Chamran, Sistan, Hajiabad, Parsi, Yavarus, Behrang, U. 520, S-83-3, D-81-18 showed a significant decrease depending on variety. Interaction between irrigation and salinity levels of irrigation water showed a non-significant effect on the leaf area, spike length, and grain yield. The results of this study revealed that the highest and lowest value for different traits was observed at 125% plant water requirement and rain fed with one supplementary, respectively where the loss percent for plant height, leaf area, spike length, 1000-seed weight, plant fresh weight, plant dry weight, spike length, number of seeds per spike, biological yield, economic yield, and harvest index were 37%, 63%, 64%, 66%, 14%, 42%, 62%, 61%, 89%, and 75%, respectively. The results of Yousfi et al., (2010) showed that salinity of irrigation water at levels of 1.8, 12 and 17 dS.m-1 and irrigation at two levels of 100 and 35% of water field capacity by soil on biomass traits plant production, plant height, biomass, leaf chlorophyll and nutrient elements including nitrogen, potassium, calcium, magnesium and phosphorus had a significant effect at 1% level. Correlation results revealed that the highest correlation between grain yield and biological yield.

In general, the results of this experiment showed that reduction of irrigation levels (percent plant requirement) leads to reduction of growth and yield characteristics of wheat. Irrigation water salinity was significant decrease at 5.4 dS.m-1 level on plant height, leaf area and 1000-seed weight. Interaction between irrigation and salinity levels of irrigation water showed a non-significant effect on the leaf area, spike length, and grain yield. The results of this study revealed that the highest and lowest value for different traits was observed at 125% plant water requirement and rain fed with one supplementary, respectively. According to high soil salinity (Table 2), observation of the highest amount of biological yield and grain yield in 125% water requirement is acceptable due to prepare the full or partial water need for salt leaching.