Cropping system optimization based on the comparative analysis of precipitation utilization in Sichuan Province

In the 8 typical stations of agro-ecological zone in Sichuan Province, analysis study on the primary planting models was done to compare the yield reduction rate related with precipitation profit and loss, risk index of yield reduction rate, rainfall use efficiency (RUE) and economic efficiency of precipitation (EEP) of the primary cropping patterns. The results showed that: (1) The averaged yield reduction rates related with precipitation profit and loss significantly varied with regions, cropping patterns, crops and crop growth stages in Sichuan Province. Spatialy, the lowest value of 23% appeared in Ya'an station, the highest value above 50% appeared in Panxi station, and 30%--40% in other regions; in cropping patterns, the value of dry triple cropping pattern with wheat-maize-Chinese trumpet creeper was lower than that of the rotation pattern with wheat-rice; in crop species, the values of winter wheat, winter rape and autumn sowing potato et al. were generally higher than that of rice, maize, cotton, sweet potato and soybean; in growth stages, the values before and after flowering of winter wheat, winter rape and autumn sowing potato were generally higher; however, values at the end stage of each crop were relatively lower. (2) Based on natural precipitation, Panzhihua and Xichang encountered the highest risk of drought, but the risk index of yield reduction rate for the dry triple cropping pattern with wheat-maize-Chinese trumpet creeper was relatively lower; due to excessive staged precipitation in most basin regions like Ya'an, the waterlodgging disaster was more severe, resulting that the rotation pattern with wheat-rice was slightly supior to the dry triple cropping pattern with wheat-maize-Chinese trumpet creeper. Based on the rainfall use efficiency (RUE) and economic efficiency of precipitation (EEP), comparing results were great consistent at all stations: the superior cropping pattern was the double cropping pattern with wheat (rape or potato)-rice followed by the dry triple crooping pattern with wheat (rape)-maize-Chinese trumpet creeper (soybean). (3) Synthetically considering the risk of drought and flood, rainfall use efficiency, economic efficiency of precipitation and complex terrain factors, the double cropping rotation pattern with wheat (rape or potato)-rice was advised in croplands with well irrigation conditions, while dry triple cropping pattern with wheat (rape)-maize-Chinese trumpet creeper (soybean) was advised in dry lands wi