关键词: 光合特性, 甘薯, 减氮运筹, 叶绿素荧光参数

Abstract: Drought is frequent and severe in Shaanxi Province because of the special geographical location and climate. Thus, it is critically needed for efficient agricultural drought monitoring and drought impact analysis using remote sensing technology. Here, we used vegetation conditionindex (VCI) as the monitoring indicator of agricultural drought at growing season to explore the applicability of VCI in agricultural drought monitoring in Shaanxi Province and its correlation with precipitation. Then VCI was adopted to identify and analyze the temporal and spatial dynamics of agricultural drought from March 2002 to May 2016. The results showed that VCI had some advantages in monitoring agricultural drought in Shaanxi Province. VCI did not show good correlation with precipitation on monthly scale, which indicated that precipitation was just one of many factors affecting vegetation coverage and growth. VCI had lag response to precipitation change, with about one month lag in Guanzhong plain and southern Shaanxi, less than one month lag in northern Shaanxi. Over the past fifteen years, agricultural drought events of Shaanxi Province mainly occurred in March, followed by October and November. While continuous agricultural droughts mainly occurred in spring or autumn, the overall drought condition had been alleviated. Theproportion of drought area was the largest in autumn and smallest in summer. The droughtfrequency was the highest in autumn and lowest in summer. Most of the region in northern Shaanxi was prone to spring drought and autumn drought, while some areas of Guanzhong plain and southern Shaanxi were prone to spring drought and autumn drought. The drought frequency was the highest in northern Shaanxi, followed by Guanzhong plain and lowest in southern Shaanxi.

Key words: nitrogen application management under reduced rate, photosynthetic characteristics, chlorophyll fluorescence parameter, sweetpotato (Ipomoea batatas)