Comparison of an aerial-based system and an on the ground continuous measuring device to predict yield of winter wheat

The objective of the research was to compare an aerial image with optical data of an on the ground platform device measuring continuously while driving through the field. For this latter, a Cropscan, Inc. multi-spectral radiometer was used to automatically take a measurement every 1-1.5 m. Field images of the normalized difference vegetation index (NDVI) of both devices were compared in their capability estimating yield variability in a wheat field. An experimental field with three seeding densities and five nitrogen application rates was investigated. Every treatment had four repetitions, resulting in 60 plots of 12 m x 16 m. At harvest, yield variables of the plots (grain and straw yield (t/ha), dry matter content in grain and straw (t/ha), nitrogen in grain and straw (kg[N]/ha) and protein content (%) in grain) were collected to relate to the images of both systems. The NDVI of both measurement systems was well related to applied nitrogen in the field: correlation coefficients were 0.78 and 0.85 for the aerial-based and the ground-based system, respectively. There was a high similarity (correlation coefficient of 0.94) between NDVI measurements of both systems. NDVI was also well related to yield variables at harvest. The NDVI of the ground system was better related to yield variables at harvest compared to NDVI of the aerial system. Best correlation coefficient found for both systems was with nitrogen in grain: 0.84 and 0.91 for the aerial-based and the ground-based system, respectively. NDVI images were more related to yield quality. Grain yield already reached its optimum in the field, while grain quality still increased with increasing nitrogen application rate. For the ground system, the average estimation errors, when using linear regression analysis, were smaller than 10% for all yield variables except for estimated straw yield and estimated nitrogen content in straw. For the aerial system, also estimated total nitrogen content exceeded the 10% error percentage. Besides the higher accuracy in the estimation of yields variables, the ground system had the advantage of being cheaper and that the data were immediately available.