Investigating the performance and water productivity of wheat cultivars in different sowing dates and irrigation conditions (a case study in Gorgan Plain)

Planting the proper cultivar in the most optimal sowing date is very decisive in the management of environmental resources, including water resources, and leads to maximum water productivity of and energy efficiency for increasing performance. Therefore, this research was conducted with the aim of determining the most appropriate sowing date and water productivity for commercial cultivar of bread wheat under supplemental irrigation and water deficit conditions in the climatic conditions of Gorgan, Iran.

This experiment was carried out as split-split plots based on randomized complete block design (RCBD) with four replications, during the 2021-2022 cropping season. In this experiment, two moisture conditions (supplemental irrigation and water deficit conditions) were placed in main plots, seven sowing dates (from 1 November to 31 December, 10-day intervals) were placed in subplots and four bread wheat genotypes (including Arman, Araz, Taktaz and N-93-9) were placed as sub-subplots.

The analysis of variance for grain yield and water productivity showed that the effect of moisture conditions was significant at the 0.05 level and the effects of sowing date and cultivar were significant at the 0.01 level. The results of mean comparisons showed that the grain yield in water deficit conditions (5288 kg ha-1) was significantly lower than the supplemental irrigation conditions (5715 kg ha-1). Water deficit conditions caused a significant increase in water productivity (17.3 kg ha-1 mm-1) compared to supplemental irrigation conditions (16.1 kg ha-1 mm-1). The highest grain yield was obtained on the second (11 November, 6340 kg ha-1) and third (21 November, 6165 kg ha-1) sowing dates. Also. the highest water productivity was related to the second and third sowing dates (18.6 kg ha-1 mm-1). The results of mean comparisons for cultivars showed that in Taktaz (as an early-maturing cultivar) grain yield (5872 kg ha-1) and water productivity (17.8 kg ha-1 mm-1) were significantly greater than other genotypes.

The results of this research showed that water deficit conditions caused a significant decrease in grain yield and a significant increase in water productivity. The highest grain yield and water productivity were obtained on the second and third planting dates. Also, grain yield and water productivity in Taktaz cultivar were significantly greater than other genotypes. In general, it can be said that the planting of Taktaz cutlivar in the second and third sowing dates (11 and 21 November) has resulted in achieving the maximum performance and water productivity in both supplemental irrigation and water deficit conditions.