Optimizing Irrigation Scheduling for Major Crops in the Middle of Iraq Using the CROPWAT Model to Promote Sustainable Agriculture: Scheduling and Water Requirements for Major Crops in Iraq

Water shortage crisis and poor water quality in Iraq represent a substantial environmental challenge caused by climate change and the constructed dams on the Euphrates and Tigris rivers in upstream countries. It is important to minimize the usage of water. Irrigated agriculture relies on surface and groundwater, rendering it the primary water consumer in Iraq. Utilizing the FAO CROPWAT 8.0 model indicated that evapotranspiration in Al-Qadisiya Governorate, the middle of Iraq, peaked in July and reached its bottom in January. A high evapotranspiration number signifies enhanced evaporation due to elevated temperatures and maximal sunlight exposure. Conversely, a low evapotranspiration value due to lower temperatures indicates lower crop water requirements. Evapotranspiration is intimately connected with the length and intensity of solar radiation. The effective rainfall values were 23.2%, 26.3 %, and 0% which were used by wheat, barley, and rice, respectively. In this study, it was obvious that the main feature of rainfall values for crops was that their amounts varied temporally. The total amount of water that wheat, barley, and rice needed for irrigation in the study area was 99.1 mm, 103.1 mm, and 404.1 mm, respectively. The data demonstrated that the irrigation need for rice (summer crops) was greater compared to other seasonal crops, such as wheat and barley. The study highlighted the fact that the crop grown in the hot season required more water consumption, which was adversely correlated with less rainfall and positively with higher Etc. On the contrary, high rainfall and lower crop evapotranspiration are prevalent in the cold season (winter season). The irrigation water needs of wheat, barley, and rice in the study area were 99.1 mm, 103.1 mm, and 404.1 mm, respectively. Furthermore, water demand remained rather stable, with a peak during the intermediate phase. This peak is essential to avoid water stress, especially during critical growth stages such as root formation stage, tillering, flowering, grain formation and dough stage, when consistent moisture is critical for optimal growth. However, water requirements declined in the later phase, reflecting the necessity of dry conditions to facilitate harvesting. The results indicated that rice requires longer irrigation periods than the other two crops due to the lack of rainfall during its growing season. The research promotes the use of CROPWAT for the calculation of crop water requirement, irrigation water requirements, and irrigation scheduling for sustainable agriculture in Iraq and globally.