Extended Abstract
1. Introduction: Agricultural plants are the primary source of the human food supply; among them, potatoes hold a special place in the human food basket. Temperature, as an ecological factor, directly and indirectly affects plants. Directly, heat impacts all vital plant processes and the intensity of their metabolism. Indirectly, it affects other critical factors such as water availability, especially in regions characterized by dry or semi-dry conditions. Climatic indices with a thermal basis, such as growth-day degree, heliothermal units, and the photothermal index, serve as useful tools for predicting crop growth and yield. Since the growth period and heat requirements vary among potato cultivars, selecting a suitable cultivar is crucial. Without proper cultivar selection, all efforts in nutritional management and weed control may prove ineffective. Therefore, conducting appropriate research to identify suitable cultivars for each region is essential.
2. Materials and Methods: This experiment was conducted as a factorial in the form of a randomized complete block design with 3 repetitions in the crop year 2022-2023, and to evaluate the life cycle of three potato varieties based on growth degree-day light and thermal indicators and its effect on yield in the research farm of Mohaghegh Ardabili University. To measure the height of the plant the number of six plants were randomly selected for each plot and then measured using a meter. The height of each of the selected plants was measured in centimeters from the soil surface to the tip of the tallest main stem in 5 steps, and the average height of plants was considered for each plot. During the vegetative growth of the potato, 3 squares (50 × 75 cm) were randomly placed in each plot, and the percentage of cover was measured visually, and the average percentage of cover of the plants was included in the calculations. Data were recorded in Excel software, and graphs were drawn with this software. Data variance analysis was performed with SAS version 9.1 software, and mean comparisons were performed using the LSD test at a probability level of 5%.
3. Results and Discussion: In the experiment, it was found that different growth stages of potato cultivars require different times and degree days. The Agria cultivar grew by 80% in 35 days by receiving 308.8 degree days. Also, this cultivar completed the emergence stage up to a height of 51 cm in 32 days by receiving 359.2 degree days, and the tuber formation stage took 1.8 days. After that, by receiving 15 degree days and 10.7 days after that, of receiving 140 days 80% entered flowering. Jeli cultivar became 80% emergence in 30 days with 263 degree days and reached the stage of emergence up to a height of 51 cm in 45.4 days with 502 degree days. Also, tuber formation in this cultivar started before reaching 51 cm, and the tuber formation stage was completed by 80% flowering after 10 days at 100 degrees. The Lady Rosetta cultivar also reached the stage of emergence up to a height of 51 cm in 51.7 days with 597 degree-days, emergence up to tuber formation in 17.6 days with 192 degree-days, and tuber formation up to 80% of flowering in 16.4 days, receiving 183 degree-days. All three cultivars completed their life cycle in 141 days from planting to harvesting by receiving 1578.5 degree days. Figure 1 shows the phenological stages of the cultivars tested. In the present experiment, it was found that the closer we get to the hot months, the amount of photothermal units received per day increases, and the growth stages go faster. The results of Table 5 show these points that the highest percentage of difference in photothermal index between treatments is 6% at the 50% emergence stage, 5% at the height of 51 cm of the plants, 2% at the 70% coverage of the plants 4% at the modulation stage and The flowering stage was 10%. Comparison of average data indicates that in weed-free conditions, the Lady Rosetta cultivar has more heat consumption efficiency than other treatments. This cultivar produces an economic yield (tuber) in 140 days from planting to harvesting for receiving fewer heat units. The cultivar Lady Rosetta was the best treatment in terms of efficiency of heliothermal use in conditions with and without weeds. According to the results, the efficiency of heliothermal consumption of Jeli cultivar decreases by 43.5% Agria by 36.7% and Lady Rosetta by 35.5% in the presence of weeds.
4. Conclusion: The results show that different potato cultivars differ in terms of agro-climatic characteristics. These differences play the main role in selecting and cultivating this product in different regions. The present experiment found that the Lady Rosetta cultivar has the most heat consumption efficiency. Therefore, this cultivar can be grown in areas where the length of the season from planting to harvesting is short due to weather restrictions. Cultivated Lady Rosetta is a semi-late cultivar and can be a good alternative to early cultivars, which have low yields.