Introduction
Potato (Solanum tuberosum L.) is considered the fourth most important food crop worldwide, following wheat, rice, and maize. Selecting an appropriate planting date that is well adapted to the climatic conditions of Khuzestan is essential for achieving economically viable potato production. Potato is relatively tolerant of low temperatures and is generally considered a cool-season crop. Optimal growth occurs in regions where the average temperature of the warmest month is approximately 25°C or lower, while the ideal temperature range for maximum tuber production is 15–22°C. In temperate regions of Iran, potatoes are typically harvested and consumed during autumn and early winter, resulting in a market supply gap during the subsequent months. Cultivating potatoes in warmer regions, such as Khuzestan, and supplying the crop during late winter and early spring could help reduce this seasonal gap. Therefore, the present study was conducted to investigate the effects of planting date and weed-control treatments on the quantitative yield of potato under the climatic conditions of Khuzestan.

Materials and Methods
To investigate the effects of planting date and weed-control treatments on the quantitative yield of potato, a split-plot experiment was conducted based on a randomized complete block design at Shahid Chamran University of Ahvaz during the 2023–2024 growing season. Planting date was assigned to the main plots at three levels: October 16, November 16, and December 16. Weed control was also investigated at six different levels on the subplots, i.e. weedy (no weed control), weed-free (complete weed control by manual weeding until the potatoes were hilled), manure (10 t ha⁻¹), manure+herbicide oxyfluorfen (1.5 L ha⁻¹ equivalent to 360 mL a.i. ha⁻¹), herbicide oxyfluorfen (1.5 L ha⁻¹) alone, and inter-row cultivation of rye as cover crop. The measured parameters included the number of branches per plant, shoot dry matter (g m⁻²), the number of large (diameter >5 cm), medium (diameter 3–5 cm), and small (diameter <3 cm) tubers per square meter, and the yield of large, medium, and small tubers (t ha⁻¹). These measurements were evaluated at both economic and physiological maturity stages.

Results and Discussion
At economic harvest, the number of tubers obtained from the October, November, and December planting dates was 44.6, 58.1, and 66.0 tubers m⁻², respectively. At physiological harvest, the corresponding values were 41.3, 55.0, and 72.7 tubers m⁻². Thus, the highest number of tubers per unit area at both harvest stages was obtained from the December planting date. Tuber yield at physiological maturity was significantly higher than that at economic maturity. The highest tuber yields at economic and physiological harvests were recorded for the December planting date, reaching 20.7 and 34.6 t ha⁻¹, respectively. The higher tuber number and yield associated with the December planting date may be related to the more favorable temperature conditions prevailing during the subsequent stages of crop development. The cooler temperatures following December planting may have promoted tuber initiation and development while extending the period during which temperatures remained within the favorable range for tuberization, ultimately contributing to greater tuber production. However, this interpretation should be considered in relation to the specific temperature conditions observed during the growing season. Among the weed-control treatments, the lowest tuber yield was recorded in the rye cover-crop treatment, which may be attributed to interspecific competition between rye and potato for water, nutrients, light, and other environmental resources. No leaf injury, including leaf burn, or plant mortality was observed following the pre-emergence application of oxyfluorfen, indicating that the treatment was well tolerated under the conditions of the experiment. Furthermore, the application of oxyfluorfen, either alone or in combination with manure, significantly increased both tuber number and tuber yield compared with the weedy control treatment.

Conclusion
Results showed that pre-emergence application of oxyfluorfen can control weeds in potato fields either alone or in combination with manure from animals. The results also indicated that Khuzestan as a subtropical region has potential for potato production and can supply potatoes to the market during off seasons when potato production in temperate regions is limited.