A crop moisture stress index for large areas and its application in the prediction of spring wheat phenology

Abstract

Crop phenology models are used in remote sensing programs for interpreting changes in spectral signatures during the growing season, in yield modeling, and in early warning of episodic events that affect crop production over large areas. An agrometeorological crop phenology model for spring wheat that incorporates the photothermal concept suggested in the Robertson crop calendar model is presented and modified to incorporate a crop moisture stress index as an additional model parameter. The crop stress index parameter is derived from comparison of crop water use under unlimited water conditions. The index may be used in other applications such as yield predictions. The influence of moisture stress on phenological development was derived from the literature. Development in general is retarded when moisture stress occurs early in the vegetative phase. Moisture deficit conditions after flowering hasten senescence, possibly through an increase in leaf temperature. Validity of the model was tested in the 1980 spring wheat areas in north Dakota, South Dakota, Minnesota and Montana. The model is flexible to incorporate remotely sensed multispectral data as inputs.