Evaluating different active crop canopy sensors for estimating rice yield potential

GreenSeeker active crop canopy sensor has been widely reported in literature for in-season nitrogen (N) management. An N fertilization optimization algorithm has been developed to use this sensor for topdressing N recommendation. An important component of this algorithm is to use crop sensor to estimate yield potential before topdressing N application. In addition to GreenSeeker, another commercial crop sensor, Crop Circle ACS - 470, has been recently developed with 6 possible spectral band choices (blue, green, two red bands, red edge and NIR). Little research has been conducted to compare these two sensors for estimating rice yield potential. The objective of this research was to determine how much improvements the Crop Circle ACS 470 would achieve for estimating rice yield potential at stem elongation stage, as compared with GreenSeeker sensor. Four N rate experiments were conducted in Jiansanjiang, Heilongjiang Province, in Northeast China in 2008 and 2009. The FieldSpec 3 hyperspectral canopy sensor was used to collect canopy reflectance, which was used to simulate spectral bands of GreenSeeker and Crop Circle sensors. The results indicated that in-season estimate of yield (INSEY) calculated with GreenSeeker NDVI and RVI could explain 42% and 62% of yield potential variability. The INSEY calculated with nine vegetation indices using simulated Crop Circle spectral bands performed better than GreenSeeker indices, with R² being 0.64-0.75. INSEY (MTCARI) had the best performance, explaining 75% of the yield potential variability, followed by INSEY (MCARI1) (R²=0.73). The preliminary result indicated that Crop Circle ACS 470 sensor could explain 13% more variability in rice yield potential at stem elongation stage. More studies are needed to more systematically evaluate all possible vegetation indices that can be calculated with Crop Circle spectral bands for estimating rice yield potential at different growth stages.