Comparing Commercial Optical Sensors for Crop Monitoring Tasks in Precision Viticulture

Abstract

The emergence of precision agriculture technologies and an increasing demand for higher quality grape products has led to a growing interest in Precision Viticulture. Actually, cultural monitoring is the most important application in PV systems: it requires specific technologies able to investigate the cultural conditions. To this aim, typically remote sensing surveys are adopted. These, anyhow, involve technical, economical and organisational barriers hampering a wide diffusion of their application. In order to overcome these problems, it would be necessary to substitute and/or integrate remote sensing information with alternative ground sensing technologies, to be employed directly inside the vineyard. This paper considers a commercial optical sensor, the GreenSeeker, useful in ground sensing surveys, and it compares its performances in monitoring vine with results obtained by a multispectral digital camera used as a tester. The experimentation was carried out in a greenhouse, on an artificial row including 15 grapevines (Cabernet Sauvignon variety). In front of the row, it was fixed a metallic rail gauge in order to permit a longitudinal movement of the Greenseeker sensor. Each plant was investigated at three different heights with a 5 s data time acquisition. Simultaneously, photos of the same grapevine were took by a multispectral digital camera, in order to obtain NDVI values through image analysis. The multispectral digital camera, normally used for remote sensing survey in agriculture, was considered as a test. Results demonstrate a strength correlation (R2 = 0.97) between the NDVI values measured through the two methods. This shows the same behaviour of the two tools, according to crop vigour and stress conditions induced into the plants. Consequently the GreenSeeker can be considered as a suitable solution for cultural monitoring in viticulture

Evaluation of “ground sensing” optical sensors for diagnosis of Plasmopara viticola on vines

“…Both proximal sensors are normally used to monitor cover crops to manage nitrogen fertilization according to the logic of variable rate application (Govaerts et al, 2007;Sripada et al, 2008). These devices were proposed to monitor crop vigour variations as an alternative to the acquisition of multispectral images (Lamb et al, 2009); in particular, Drissi et al (2009) and Mazzetto et al (2009) suggested the application of the GreenSeeker to monitor vigour variations of Vitis vinifera plants in vineyards. Previous experiences were carried out by the authors in field using a mobile lab equipped with GreenSeeker sensor, in order to evaluate its efficiency in detecting the dynamic diffusion of disease incidence directly in vineyard (Mazzetto et al, 2010(Mazzetto et al, , 2011.…”

Segmentación automática de imágenes digitales para estimar el vigor en viñas

“…The latter, in particular, has been used in vineyard fields to sense canopy reflectance and calculate vegetation indices, which have been further related to canopy porosity (Tardáguila et al, 2008), leaf area index projected onto a vertical plane (VLAI) (Drissi et al, 2009), and pruning weight (Stamatiadis et al, 2006). Mazzeto et al (2009) corroborated the feasibility of calculating standard vegetation indices such as the NDVI with Greenseeker TM in vineyards; nevertheless, these commercial devices are not polyvalent and the information obtained from them has seldom taken part in decision making algorithms of PA applications. Some of them can only be used in bulk crops or do not incorporate GPS receivers, which complicates the sharing of data coming from other sensors with the final goal of explaining variability and casting predictions.…”

Test of Ground-Sensing Devices for Monitoring Canopy Vigour and Downy Mildew Presence in Vineyards: First Qualitative Results

“…The threshold value applied is 0.60 and it was selected in order to emphasise the small differences in vegetative vigour level within the vineyard. This value has been identified through the examination of values proposed in literature and the frequency analysis of data collected during preliminary tests carried out in greenhouse [Mazzetto 2009]. NDVI maps clearly show differences in vegetation conditions in the two groups of rows.…”

“…Currently, there are several commercial active optical ground sensing devices available: one of the most used devices is the GreenSeeker RT100 (Ntech Industries Inc., Ukiah, USA). Recently the GreenSeeker application in viticulture has been studied to characterise spatial distribution of vine vegetation vigour [Drissi 2009;Mazzetto 2009]. Groundsensing optical sensors were also investigated to detect disease symptoms on wheat and to discriminate between pathological and nutritional stresses [Moshou 2006].…”