修订后水分盈亏指数在甘肃省冬小麦干旱监测中的应用

提高西北旱作农业干旱监测准确性和时效性,对农业生产防灾减灾有重要意义。利用甘肃省3个农业气象观测站长期土壤水分和冬小麦生育状况观测资料、1971—2016年43个冬小麦种植县气象观测资料及产量资料,基于冬小麦播前底墒和生育期水分盈亏量修订了作物水分盈亏指数,并确定了干旱等级指标,改进后作物水分盈亏指数与土壤贮水和冬小麦减产率高度相关,能更准确的反映甘肃省冬小麦干旱实况,并利用ArcGIS分析了近46 a甘肃省冬小麦不同生育期、不同等级干旱发生频率的时空分布特征。结果表明：甘肃省冬小麦从播种至开花期随着发育期推移,呈现干旱频率增加、范围扩大的趋势,多以中旱居多,其中拔节—开花期发生面积最大,陇中、庆阳市北部、平凉市西部、天水市西部、陇南市南部干旱出现频率较高;开花—成熟期随着降水量增加干旱发生频率减少、程度减轻。

Applicability of modified water budget index in winter wheat drought monitoring of Gansu Province

Winter wheat is a major grain crop in Gansu Province, where precipitation is the most limiting factor for winter-wheat production. The uneven space-time distribution of precipitation results in perennial winter-wheat drought in the province. Therefore, it is of great significance to improve the accuracy and timeliness of drought monitoring in dryland agriculture in northwestern China. This could provide the needed scientific basis for decision-making departments to formulate agricultural-disaster prevention and mitigation measures in support of regional food security. In the present study, we collected multiyear data on soil-water content and winter-wheat fertility from three agronomic observatory stations as well as daily observational data on meteorological elements for 43 winter-wheat-growing counties during 1971-2016. On the basis of soil-water content before sowing and on water budget for winter-wheat development stages, the crop water-budget index was revised, and the drought index for different grades was then determined. The correlation coefficient between the water-budget index and soil-water storage was 0.6522. The high correlation between the water-budget index for different growth periods and winter-wheat yield reduction rate passed a 0.01 test of significance. This showed that the modified water-budget index can accurately reflect winter-wheat drought for Gansu Province. Results of using ArcGIS to map the spatial distribution （including intensity and frequency） of drought at different wheat-growth stages in the years 1971-2016 show that the winter-wheat drought occurrence and range in Gansu Province increased with each growth stage from sowing to flowering. The drought distributions during the jointing and flowering periods were the the most widespread, occurring in central Gansu Province, north of Qingyang, west of Pingliang, west of Tianshui, and south of Longnan. The frequency and level of drought in the mature （flowering） period decreased with increasing precipitation. Thus, the modified crop water-budget index objectively reflected winter-wheat drought in Gansu Province, thereby providing a reliable reference application.