Introduction
Precipitation and nitrogen are the most abiotic factors that greatly impact the yield of barley in arid and semi-arid regions. Because with water restrictions in dryland conditions, Iran's drylands have low organic matter and mineral nitrogen () for barley plant nutrition. Researchers believe, the production of dryland barley is often influenced by the three factors of planting date, soil available water and determining the exact nitrogen requirement of this crop. Therefore, many researchers have reported the existence of interaction effects between water (supplemental irrigation) and nitrogen in barley plants. Because nitrogen through the expansion of the plant's root system, it causes better absorption of nutrients and water and as a result increases water use efficiency. Therefore, the main purpose of this experiment was to evaluate the interaction effects of nitrogen and supplemental irrigation in the production of new barley lines, to increase yield and introduce them for cold areas.
Materials and Methods
The experiment was conducted in a split split-plot arrangement in a randomized complete block design (RCBD) with three replications and for two cropping years (2021-2023) in the Dryland Agricultural Research Institute (DARI). Factors included supplemental irrigation with two levels (50 mm in autumn and 50 mm in autumn + 30 mm in end of stem elongation stage (ZS77)) in main plot, nitrogen 5 levels (0, 30, 60, 90 and 120 kgN.ha-1) in sub-plots and five rainfed barley genotypes (Artan, Ghaflan, ERBYT 8-(96-93), ERBYT 8-(95-92) and ERBYT 22-(93-90) in sub sub-plots. The barley genotypes were planted on a flat plot area by Hassia planter in 11-row plots with 15 m long and 2.2 m wide (20 cm row spacing). The sowing rate was 380 seeds per m2 based on thousand kernel weight (TKW) of each genotype. Seeds were treated by Penconazole fungicide. The planting dates were September 22-28. Plant traits including water use efficiency (WUE), Agronomy nitrogen use efficiency (NUE), nitrogen partial factor productivity (PFP), biological and grain yield, yield components, canopy temperature (TC), were measured. To analyze the results, analysis of variance and, regression models were used.
Results and Discussion
The results showed that the effect of year was significant (P≤0.01) on the biological and grain yield due to the increase in rainfall (58 mm) in the early spring in the second year. An increase in early spring rainfall causes an increase in plant canopy and number of spikes per m2 and a significant decrease in the canopy temperature by 7.5 °C. With the increase of each millimeter of rainfall, the nitrogen partial factor productivity (PFP) increased by 41 kg yield/kg N. A significant difference was observed between the two supplemental irrigation levels in most of the plant characteristics including biological and grain yield. This increase was due to a significant increase in the spikes.m2. The effect of nitrogen on biological and grain yield was significant (P≤0.01). With the increase of nitrogen application rate, nitrogen use efficiency (NUE) and nitrogen partial factor productivity (PFP) decreased significantly. Nitrogen application reduced canopy temperature (TC) by 2 °C and NUE and PFP by 47 and 104 kg yield/kg N, respectively. Nitrogen application reduced the effects of water and heat stress in the grain filling stage and on average increased WUE by 48 and 56% for grain and biological yield, respectively. There was a significant difference (P≤0.01) between the barley genotypes in terms of biological, grain and straw yield. The highest biological yield of 8419 kg/ha was obtained from Artan cultivar and the highest grain yield was obtained from Artan, Ghaflan number 3 genotypes with an average of 3635 kg/ha. These three genotypes had the highest partial factor productivity (PFP) with an average of 69.7 kg/kg. The average water use efficiency (rainfall + supplemental irrigation) for the production of biological and grain yield, these three genotypes was 22.3 and 9.9 kg/ha/mm, respectively. WUE for the superior Artan genotype, 22.9 and 10 kg/ha/mm, respectively. The interaction effect of supplemental irrigation and nitrogen on grain yield was significant (P≤0.01). The calculations showed that the contribution of nitrogen fertilizer in the production of barley grain yield 16.3% was more than soil nitrogen. Finally, two stages of supplemental irrigation (50 mm at planting time + 30 mm at end of steam elongation) with 30 kg/ha nitrogen application was the best term.
Conclusion
The interaction effect of supplemental irrigation and nitrogen in the production of barley genotypes was obtained by improving plant health indices, reducing the canopy temperature and increasing the number of spikes per m2. Supplying the nitrogen requirement of barley under supplemental irrigation conditions to reduce the effects of moisture and heat stress on the plant was proved in this research. |
