Vegetation indices obtained from satellite images are widely used in the monitoring of agricultural crops and the prediction of yields. The changes in meteorological factors and especially the irregular rainfall regime have positive and negative effects on different ecological regions. The aim of this study is to investigate the relationships between spectral vegetation indices, yield and biomass on the basis of agricultural climatic regions (ACZ) and to determine effective vegetation indices on a temporal basis. In this context, 5 different regions were determined by using aridity index and growing degree days (GDD) parameters in establishing ACZ. In the field studies, the plant samples were collected from 108 plots of wheat cultivated in Ankara and Konya provinces and yield and biomass values were obtained.

During the crop growing period, Normalized Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) of 15 different periods from MODIS satellite image were used. The relationship between vegetation indices and biomass and yield was examined by Pearson correlation coefficient. The highest correlation between vegetation indices and biomass was observed in May in 12th period (75%) and 13th period (72%) for NDVI, 12th period (71%) and 13th period (72%) for EVI. The highest correlation rate between vegetation indices and yield was determined as NDVI (72%) and EVI (70%) in the 12th period. During the vegetation period, the 12th and 13th periods correspond to the heading / anthesis period.

Linear regression models were created according to the significance levels (p <0.05) of the parameters. The R2 values for the vegetation indexes determined for ACZ-based models ranged from 0.37 to 0.87 for biomass-NDVI and 0.56 for the whole area, 0.24 to 0.68 for the biomass-EVI and 0.52 for the whole area. These ratios vary between 0.28 and 0.72 between yield and NDVI, whereas 0.53 in whole area. The yield-EVI ranges from 0.32 to 0.54, while it is 0.48 for the whole area. In ACZ based estimation models, a higher level of relationship was obtained than the model made for the whole area.