Use of hyperspectral remote sensing in evaluating the rate of net photosynthesis and stressed areas of agricultural fields

Crop growth and development is a function of various limitations imposed by soil properties and management practices coupled with transient conditions as presented by the weather within the growing season. One way to assess crop development is through the use of the radiation use efficiency and water use efficiency, each of which relate to current crop ecophysiological status. These can be determined using micrometeorological methods from measurements over agricultural surfaces in an upwind area from an instrumented tower. In relating carbon and water exchanges over larger spatial areas, remote sensing is key. The advantage of hyperspectral reflectance (HR) is that individual pigments or physiological features can be identified and exploited. The work presented, examines the relationship between temporally discrete HR indices and continuous micrometeorological data. Using ground-based HR measurements, we show that the canopy gross photosynthetic rate is associated with the photochemical reflectance index (PRI) and that canopy water content is related to the water band index (WBI). These relationships are expanded to the field scale through the use of CASI imagery for several years and crops. In our study field, HR successfully identifies areas of potential stress that are correlated with low yield as determined with a final harvest yield map.