Introduction
Bread wheat is the most important cereal and the source of calories in human nutrition worldwide. The effect of moisture stress on the quality properties of wheat is complex and is influenced by genotype, environment and their interaction. Superabsorbent polymers last for 5 -7 years in soil and can absorb water up to 200 to 400-fold of their own weight. Superabsorbent polymers are divided into two major groups, depending on their source: natural-based mateials, such as animal manures, and chemical materials. This experiment aimed to study the response of bread wheat cultivars to moisture stress and the ameliorative effects of superabsorbants on these responses.
Materials and Methods
In order to investigate the adverse effects of drought stress on wheat cultivars in the presence of different superabsorbent treatments, two separate experiments were conducted in Urmia and Khoy cities located in West Azerbaijan province, Iran. The experiments were carried out as a split factorial based on a randomized complete block design with three replications in two years (2019 and 2020). The main factor was the three moisture regimes including irrigation after evaporation of 70, 140, and 210 mm water from the class-A pan. The combination of levels of different superabsorbent treatments in wheat cultivars formed the sub-factor levels: cow manure at a rate of 40000 kg/ha (as a natural superabsorbent), chemical superabsorbent (Taravat A-200) at a rate of 200 kg/ha,  and no use of superabsorbent (control) along with two commercial cultivars of bread wheat, Mihan and Heidari. Bartlett's test was performed for the uniformity of the variances of the experimental errors. A combined analysis of variance of the two years was conducted after ensuring the uniformity of the variances of the experimental errors. The comparison of means was done with Duncan's multi-range test at the five percent probability level with MStatc statistical software.
Results and Discussion
The combined analysis of variance showed that the effects of different levels of treatments and their interactions were significant at 5% probability level for plant height, grain yield, grains/spike, 1000 grains weight, concentration of nitrogen, phosphorus and potassium in shoot. The highest grain yield in both locations (Urmia and Khoy) was observed for the Mihan cultivar when irrigated after 70 mm evaporation and using the chemical superabsorbent treatment, with 7930 and 7760 kg/ha in the mentioned locations, respectively. In contrast, both Mihan and Heydari cultivars had the lowest grain yield of 1490 and 2110 kg/ha in Urmia and Khoy cities, respectively, when irrigated after 140 mm evaporation and no use of superabsorbent. The concentration of nitrogen and potassium in the shoot in the presence of superabsorbent treatment was higher than those of manure and the control treatments. Meanwhile, the concentration of phosphorus in the shoot in the presence of manure treatment was higher than those of the superabsorbent and the control.
Conclusions
Based on the results of our experiment, using superabsorbent and animal manure as a natural superabsorbent, appeared as suitable solutions to reducing the adverse effects of drought stress on wheat crop in arid and semi-arid areas of the West West Azerbaijan province.