Water requirement characteristics and the optimal irrigation schedule for the growth, yield, and fruit quality of watermelon under plastic film mulching

The challenge to sustainable agriculture under increasing water scarcity has led to the notion of water-saving irrigation. In this study, we designed a special closed cultural system which can avoid water loss from soil surface and soil leakage. By using this system, we determined that at least 117.5 kg water was required for the whole life of one watermelon and the proportion of water requirement in the seedling, flowering, expanding, and mature stage was 10, 15, 65, and 10%, respectively. The potentially maximum irrigation water use efficiency (iWUE) for watermelon cultivation was 42.1 kg m−3. For watermelon cultivation under plastic film mulching, the optimal irrigation amount was 1800 m3 hm-2 and the proportion of irrigation amount in the seedling, flowering, expanding, and mature stage was 10, 15, 65, and 10%, respectively. Under this irrigation schedule, the iWUE was 26.19 kg m−3. These results are of great reference values for water management in watermelon production and indicate that there is still great potential for improving iWUE. Additionally, due to its better performance in arising soil temperatures, transparent film mulching is better to increase watermelon quality and yield than black film and grey-black film mulching in early spring cultivation.