Deteksi Dini Tanaman yang Mengalami Kekurangan Air untuk Menentukan Waktu Pengairan

Abstract

Detection of water stress in plants may help to schedule irrigation and improve water use eflciency. The objective ofthis study was to determine the reflectance vegetation index (RVI) obtained from remote sensing of the crops during soil drying and fully watered plots as a tool for detection of water stress. RVI was calculated from incoming (PAR;) and reflected (PARc) photosynthetically active radiation andfrom incoming (NIQ and reflected (NIc) near infrared radiation using the equation RVI= (NIc/NIQ/PARc/PARi). The effects of soil drying on leaf expansion, biomass accumulation, abscisic acid (ABA) in xylem sap and leaf water potential were used as drought indicators in n~uizeg rown in lpimeter in the field. Leaf area expansion and biomass accumulation were decreased by drought. The reflectance vegetation index was measured when green crop area index increased during the vegetative stage of growth. Xylem [ABA] increment coincided with decrease in RVI of drought plants. Changes in RVI of drought plants which were compared to R VI of fully irrigated reference plants occurred at early stages of drought stress when relative uvailahle soil water content was 60%. RVI was highly correlated with green crop area index (~*=0.84a)n d biomass accumulution (~'=0.88). We suggest that measurements of RVI in drought field plants compared to RVI measurements qfjiillly irriguted reference plants within the same field can be used as an early warning system of irrigation.