Simulating sugarcane yield potential and yield gap in the low latitude plateau of China based on APSIM

Sugarcane is one of the major sugar crops in the dominant sugarcane areas of Yunnan Province of China, located in the traditional low latitude plateau with the most abundant ecological regions for sugarcane growing. In this study, the cane yield potential and yield gap matters were analyzed to greatly promote cane production on large scale. The meteorological data was collected from 1981 to 2010 across 17 locations under varying ecotypes, and then combined with data obtained from the field experiments and APSIM (Agricultural Production Systems sIMulator) modeling. The simulation was performed on the cane yield and sugar content of dominant sugarcane cultivars under full irrigation and nature rain-fed conditions in different ecotypes regions. The results indicated that there were significant differences in the low-latitude plateau, while the large interannual varied greatly from the different levels of the cane yield potential and yield gaps. Furthermore, the yield potential was 123.1-134.6 t/hm2 under the typical spring planting conditions, if as humid region, or 99.3-132.7 t/hm2 if as a semi-humid region. Although the actual cane yield reached 72 t/hm2, there were still 25.2% to 45.4% cane yield potential, 7.4% to 11.1% sugar content yield potential, and 25.5% to 49.7% sucrose yield potential were expected in the low latitude plateau. Three key elements were selected to enhance the yield potential of sugarcane, including the suitable ecological climate, the optimization of sowing date, water, and nitrogen management, as well as the promotion and planting of excellent sugarcane varieties. The humid region presented sufficient precipitation, indicating the small gap of cane yield potential between irrigation and rainfed condition in terms of ecological climate. By contrast, there was no significant between the irrigation and rainfed cane yield, leading to a decrease in the sugar content. Therefore, the natural rainfed was suitable as the main sugarcane planting strategy in a humid region, particularly on the higher and stabler cane yield. There was a significant yield increase by irrigation in the semi-humid region with insufficient precipitation, due to the larger irrigation-rainfed yield gap. It was more suitable for water-saving irrigation as the main sugarcane planting strategy, focusing on the higher sugar content and water-nitrogen use efficiency. In terms of sowing season and water-nitrogen management optimization, the spring cane presented moderate growing days (360 d), moderate water-nitrogen demand (N-fertilization 120 kg/hm2, irrigation 656 mm in humid regions, and 970 mm in semi-humid region), which was far lower than that of the autumn cane demand (growing 480 d, N-fertilization 240 kg/hm2, irrigation 964 mm in the humid region and 1 342 mm in the semi-humid region), meanwhile the spring cane still remained the relatively high cane yield (122-133 t/hm2). The spring cane dominated the planting mode and combined with the optimization of the sowing-date. The water-nitrogen management was widely accepted as effective cultivation to improve the sugarcane yield and water-nitrogen use efficiency in the low latitude plateau. In the promotion of excellent cultivars, the YZ0551 was recommended as the main cultivar in both humid and semi-humid regions for outstanding cane yield performance. GL05136 was also recommended as the main cultivar in the humid region for its outstanding sugar content performance. The finding can provide a basis for the sustainable development of the sugarcane industry in the low-latitude plateau cane area, especially water-saving and drought-resistant cultivation.