Response of Eight Soft Wheat (Triticum aestivum L.) Cultivars to Different Planting Dates

Wheat (Triticum aestivum L.) is one of the most important cereal crops in the world and is a key ingredient in the manufacture of many ready-to-eat products (Chen et al., 2025). Iraq is one of the countries that relies heavily on wheat for human and animal nutrition (Qasim, 2024). Wheat provides 20% of calories and 23% of protein, in addition to minerals and vitamins that humans need (Shewry and Hey, 2015). Plant breeders face many challenges in dealing with fluctuations in environmental and climatic conditions, such as temperature, light intensity, drought, and salinity, in order to achieve self-sufficiency to meet the needs of an ever-growing population (Okello et al., 2021). Iraq’s production in 2024 amounted to approximately 5.234 million tons, an increase of 22.17% compared to its production in the previous year (2023), which amounted to 4.248 million tons, and an increase of 19.88% compared to the average for the years 2019-2023 (FAO, 2025). In the Middle East, Iraq is one of the countries most affected by climate change. In recent years, Iraq has experienced significant climatic changes, including sharp increases in temperatures reaching 52°C in some areas, and a decrease in water levels and rainfall rates (Al-Jaf et al., 2025). Climate change will lead to significant yield losses compared to previous and historical years, emphasizing the urgent need for climate change adaptation strategies. Wheat yields in all regions are expected to decrease by -18% to -20% by 2040, and by -28% to -27% by 2070 (Tita et al., 2025). Planting time is a key input for field crops. Optimal planting dates are affected by climate change, so determining the optimal planting date is essential for achieving optimal plant productivity. The temperature and relative humidity of the atmosphere throughout the growing season have a direct impact on crop production characteristics. Consequently, in order to attain high production, it is imperative to satisfy the temperature needs of wheat cultivars (Paknejad and Ilkaee, 2021). Varieties are an entry point for crop improvement and increased productivity, as they possess genetic diversity that is responsible for the main agronomic traits. The selection of these varieties directly affects vegetative growth and their ability to adapt to environmental conditions. For example, studies conducted in Nineveh Governorate in Iraq showed that the early date of wheat planting was superior to the studied traits. Similarly, there were significant differences between varieties (Abd Al-Dahi and al-Taweel, 2021).

Seeds of local wheat (Triticum aestivum L.) varieties shown in Table 1 were planted on three dates (November 25, December 10, and December 25), in one of the agricultural fields in Nineveh Governorate, northern Iraq, using a randomized complete block design with three replicates.

Each variety’s seeds were planted in two lines, each 2 meters long, with a 20-cm gap between plants and a 30-cm gap between lines. Two batches of 45% urea fertilizer were applied at a rate of 20 kg of nitrogen per dunum, one during planting and the other before ear development. A randomized complete block design was used to evaluate the data (R.C.B.D.) (Antar and Al-Wakaa, 2017). The studies were conducted on five randomly selected plants, and the following traits were studied.

Table 1: Database of wheat varieties used in the study (Iraq Ministry of Agriculture, 2024).

• The number of days before 50% of the spikes appear from the flag leaf after planting and flowering.
• Plant height (cm): The height of the plant was measured in centimeters from the soil’s surface to the top of the spike.
• Flag leaf area (cm2): Flag leaf area (the last leaf at the top of the plant) was estimated using the equation (leaf length × leaf width from its midpoint × 0.95). Flag leaf area was measured at the end of the spike-out stage.
• Number of spikes in one plant.

Results showed highly significant differences between the studied wheat varieties in the number of days required to reach 50% flowering. Table 2 shows that the variety “Sham 7” was the most delayed in flowering, recording the highest average number of days at 101.778 days. In contrast, the variety “ Adana 99” was the earliest in flowering, recording the lowest average at 84.778 days. These results are consistent with those of (Kumar et al., 2013) and differences are mainly attributed to genetic variations between the varieties, which determine their response to environmental conditions and the length of their vegetative growth period before transitioning to the flowering stage.

Planting dates had a clear effect on the number of days to 50% flowering. Delaying the planting date gradually shortened this period. The first planting date on November 25 achieved the longest period to reach flowering, with an average of 94.833 days, followed by the second date on December 10, with an average of 92.083 days. The third and last date, December 25, recorded the shortest period to reach flowering, with an average of 85.291 days. which were reflected in the varieties’ response to environmental conditions, especially temperature (Hossain and Da Silva, 2012) and rainfall rate (Ahmed, 2015).

There was a significant interaction between the effect of each variety and planting date on the number of days to 50% flowering, meaning that the response of varieties to different planting dates was not uniform. For example, the variety “Baghdad 1” recorded the longest period to reach flowering, which was 105.667 days when it was planted on the first date (November 25), while the variety “Abaa 95” recorded the shortest period, which was 78.333 days when it was planted on the last date (December 25). In general, it can be observed that early varieties such as “Adana 99” and “Abaa 95” benefited greatly from late planting to shorten the growth period, while late varieties such as “Sham 7” and “Baghdad 1” still required a relatively longer period even with late planting dates. The results were consistent with (Sarhadi et al., 2024; Albarwary and Alrijabo, 2022).

Table 2: Number of days from planting to 50% flowering for the studied cultivars.

The results of the statistical analysis shown in Table 3 revealed significant differences between the wheat varieties studied in terms of plant height. The variety (Babil 113) was the tallest with an average height of 81.666 cm, significantly surpassing the other varieties. In contrast, the variety (Buhuth 10) recorded the shortest height with an average of 62.688 cm. These differences indicate that the genetic characteristics of varieties play an important role in determining plant height, and the results were consistent with (Al-Sadoon et al., 2023).

Planting dates had a significant effect on average plant height. The first planting date (November 25) was the best, with an average height of 75.691 cm, surpassing the second date (December 10) with an average of 70.716 cm, and the third date (December 25) with an average of 66.100 cm. This superiority of the first date is consistent with what was mentioned by Hussain et al. (2002), that the first planting date surpassed the second and third dates in terms of plant height, indicating that the environmental conditions associated with early planting were more suitable for plant growth and increased height.

The interaction between variety and planting date had a significant effect on plant height. The strongest and highest interaction was between variety (Babil 113) and the first planting date (November 25), with this interaction recording the highest value of 87.667 cm. This was consistent with (Sarhadi et al., 2024), indicating that varieties with high genetic potential for height growth respond better to the environmental conditions provided by early planting dates. This was consistent with (Kumar et al., 2024; Al-Falahi et al., 2021; Altai et al., 2024).

Table 3: Plant height in cm for the studied varieties.

The results in Table 4 show clear significant differences between the wheat varieties studied in terms of flag leaf area, with the Babil 113 variety significantly outperforming the others, recording the highest average of 43,241 cm2, followed by the Rashid variety with an average of 40,993 cm2. In contrast, the variety Buhuth 10 recorded the lowest average of 23,425 cm2, indicating genetic variation between varieties in their ability to form a larger flag leaf area. This is consistent with what (Kumar et al., 2013) pointed out in their studies on genetic diversity in the vegetative growth traits of wheat.

The results showed that planting dates had a significant effect on flag leaf area, with the first date (November 25) recording the largest average flag leaf area of 34.444 cm², while the area gradually decreased with delayed planting, reaching 30.475 cm² on the second date (December 10) and 28.147 cm² on the third date (December 25). This decline is attributed to the fact that plants planted at later dates are exposed to less favorable environmental conditions, such as lower temperatures or shorter growth periods, which reduce vegetative growth and flag leaf size. These results are consistent with the findings of (Sarhadi et al., 2024; Altai et al., 2024), who confirmed that early planting contributes to improved vegetative growth and larger flag leaf area.

The interaction between varieties and planting dates had a significant effect on flag leaf area, with the interaction between the Babel 113 variety and the first date achieving the highest value of 46.587 cm², while the interaction between the Bahoth 10 variety and the third date recorded the lowest leaf area of 20.797 cm² (Al-Sadoon et al., 2023; Al-Falahi et al., 2021). This indicates a clear interaction between genetic and environmental factors in determining flag leaf growth efficiency. These results point to the importance of selecting the appropriate variety with the optimal planting date to achieve the best flag leaf area performance.

Table 4: Flag leaf area (cm²) for the studied varieties.

Results in Table 5 show a significant variation in the average number of spikes per plant among the varieties studied. The varieties “Babil 113” and “Sham 7” produced the highest number of ears, with averages of 5.094 and 5.063 spikes/plant, respectively, significantly outperforming the other varieties. In contrast, the “Adana 99” variety recorded the lowest number of ears (2.46 spikes/plant). This is consistent with (Al-Sadoon et al., 2023), that these results indicate fundamental differences in the genetic ability of varieties to produce ears, highlighting the importance of selecting the right varieties to achieve maximum productivity.

Planting dates played an important role in determining the average number of spikes per plant. The first (November 25) and second (December 10) planting dates significantly outperformed the third planting date (December 25), which resulted in the lowest average number of spikes (3.431 spikes/plant). This is consistent with (Sarhadi et al., 2024), and indicates that environmental conditions during the early planting periods, such as temperature and humidity, were more favorable for ear growth and production than the conditions prevailing during the late planting date.

Analysis of the interaction between varieties and planting dates revealed a significant interaction, with the best interaction observed between the “Babel 113” variety and the first planting date (November 25), resulting in 5.526 spikes/plant. This positive interaction indicates that this particular variety responds better to early planting conditions, enhancing its ability to produce a greater number of spikes. These results are consistent with (Altai et al., 2024), confirming the importance of considering both variety selection and optimal planting date to obtain the best results.

Table 5: Number of spikes per plant for the studied varieties.

Table 6 shows the correlation analysis between the studied traits. The positive correlations were divided into three types: the strong correlation was between plant height and flag leaf area (r=0.845), the medium positive correlation was between plant height and spike count (r=0.627), and between flag leaf area and spike count (r=0.593). The weak to medium positive correlation was between the number of days to 50% flowering and plant height (r=0.483). The results were consistent with what (Prakash et al., 2023), who studied the linkage of traits in the genetic makeup of wheat (Triticum aestivum L.): implications for breeding programs.

Table 6: Correlation between the studied traits.

In light of the obtained results, the study offers the following recommendations:

1. Varieties varied in their response to planting dates, and the Babylon 113 variety can be used in agricultural production programs, particularly in the northern regions of Iraq, due to its superior performance in key agronomic traits and proven genetic stability across different planting dates.
2. Early planting is an effective agricultural practice, given its positive impact on improving the number of days to 50% flowering, plant height, flag leaf area, and the number of spikes per plant. This effect has contributed to improved resource use efficiency.
3. Focus on the interaction between variety and planting date in applied research and crop improvement programs. Different results may be obtained when studying other dates or studying the same dates over multiple seasons.

We thank the workers in the field where the experiment was conducted, and we also thank the workers of the field crops laboratory of the Agricultural Technical College.

Nineveh Governorate, one of the governorates of Iraq, is characterized by its high production of wheat and is considered the highest in Iraq. Therefore, this article aimed to study the effect of different planting dates on different types of wheat in order to increase production.

Yarub Samer Ahmed Alnuimy: Essay Idea Formulation and Supervision.

Omar Ahmed Fathi Al-Rubaie: Field supervision with some practical experiments.

Azhar Idrees Thanoun Khattab: Field supervision with some practical experiments.

Sarah Mohammed Ali Al-Jubouri: Data Collection

Wadhah Thabit Abed Al-Dahi: Data Analysis with Feedback.

Ali M. Saadi: Article Writing, Formatting, and General Supervision.

The authors declare that no generative AI and AI assisted technology was used in the creation of this manuscript.

The authors have declared no conflict of interest.