Abstract
Although it is common to consider crop height in agricultural management, variation in plant height within the field is seldom addressed because it is challenging to assess from discrete field measurements. However, creating spatial crop height models (CHMs) using structure from motion (SfM) applied to unmanned aerial vehicle (UAV) imagery can easily be done. Therefore, looking into intra- and inter-season height variability has the potential to provide regular information for precision management. This study aimed to test different approaches to deriving crop height from CHM and subsequently estimate the crop coefficient (Kc). CHMs were created for three crops (tomato, potato, and cotton) during five growing seasons, in addition to manual height measurements. The Kc time-series were derived from eddy-covariance measurements in commercial fields and estimated from multispectral UAV imagery in small plots, based on known relationships between Kc and spectral vegetation indices. A comparison of four methods (Mean, Sample, Median, and Peak) was performed to derive single height values from CHMs. Linear regression was performed between crop height estimations from CHMs against manual height measurements and Kc. Height was best predicted using the Mean and the Sample methods for all three crops (R2 = 0.94, 0.84, 0.74 and RMSE = 0.056, 0.071, 0.051 for cotton, potato, and tomato, respectively), as was the prediction of Kc (R2 = 0.98, 0.84, 0.8 and RMSE = 0.026, 0.049, 0.023 for cotton, potato, and tomato, respectively). The Median and Peak methods had far less success in predicting both, and the Peak method was shown to be sensitive to the size of the area analyzed. This study shows that CHMs can help growers identify spatial heterogeneity in crop height and estimate the crop coefficient for precision irrigation applications.
Highlights
Machado et al [5] found a relationship between corn height variability in the field and yield, especially in drought conditions, which was influenced by water use, soil characteristics, and elevation
Repeated unmanned aerial vehicle (UAV) survey flights were performed over five fields in Israel (Figure 1, Repeated UAV survey flights were performed over five fields in Israel (Figure 1, TaTable 1): a cotton field near Megido airfield in the Jezreel valley, two tomato fields in ble 1): a cotton field near Megido airfield in the Jezreel valley, two tomato fields in Gadash
Plant heights were measured in the field using a handheld ruler
Summary
Farmers use height measurements to assess plant characteristics, such as biomass, leaf area index, and yield [1,2,3]. The height of those crops represents the growth stage and is linked to crop water consumption [4]. The most common practice is the manual measurement of several plants in a location convenient to the farmer, according to which the whole field is uniformly managed. This method ignores the spatial variability in most fields, and optimal management adapted to that in-field variability is not practiced. Maps of the current crop height can help farmers make informed decisions and manage the field by zones
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
