Monitoring barley and corn growth from remote sensing data at field scale

Vegetation indices have been used for operational quantitative monitoring of vegetation. Here, corn and barley cultures have been used to relate meaningful biophysical parameters such as dry biomass and Crop Growth Rate (CGR) to the well-established Normalized Difference Vegetation Index (NDVI). We explain these relationships by means of the use of the Light Use Efficiency (LUE) models, based on the positive relation between primary production and Absorbed Photosynthetically Active Radiation (APAR). In these models we introduce NDVI as a linear estimator of f APAR. Experimental data over corn and barley show that dry biomass is linearly related to the Time-Integrated Value of the NDVI (TINDVI). The characteristic plateau stage of NDVI coincides temporarily with the linear growth phase. During this stage both NDVI and maximum CGR remain constant for well-watered crops. Water status of vegetation is a relevant parameter because it can modify substantially the relationship between CGR and NDVI. Under this assumption it can be established that NDVI at plateau stage, represents an estimator of the potential rate of dry matter accumulation, dependent on crop and environmental variables.