EFFECTS OF PLANTING DATE ON WATER REQUIREMENTS OF MAIN VEGETABLE CROPS IN SAUDI ARABIA

The effects of planting date on the evapotran-spiration (ETC) were studied for Tomato, Egg-plant, Squash, Cucumber, Carrot, Potato, Onion, and Watermelon, in Riyadh, Makkah, Njran, Al-Qassim, Eastern region, Tabuk, Al-Jouf, Aseeir, Al-Madenah, Hail and Jazan Regions based on the crop pattern in each region. The ETC of each crop was estimated based on Penman-Monteith Equa-tion. The results showed that the ETC for crops planted in January, February, March, April or May
were higher than those crops planed in September, October, November, or December. The average ETC was higher when planting date was closer to summer months (June, July and August). Also, the results showed differences in ETC among the dif-ferent regions. The ETC in Al-Madenah region was higher than the other regions for Tomato and Eggplant. While, Riyadh region had the highest ETC values compared with the other regions for Squash, Cucumber, Carrot, Potato, Onion, and Water melon