A relationship between increasing midday canopy PAR intercepted by orchard tree canopies and increasing productivity has been well documented (Jackson, 1980; McFadyen et al., 2004, Robinson and Lakso, 1991; Wagenmakers and Callesen, 1995). However, collecting data on canopy light interception in orchards is time-consuming, and it is difficult to measure large areas. Several different methods of estimating canopy light interception have been used including fisheye photography (Robinson and Lakso, 1991). Wunsche et al. (1995) used a series of light sensors moved on a trailer through the orchard, while Giuliani et al. (2000) used a portable light bar with 48 phototransistors and a Teflon diffuser. A commercially available PAR-sensing bar (Ceptometer; Decagon Devices, Pullman, WA) was used by Grossman and DeJong (1998) and McFadyen et al. (2004) to take multiple readings in a regular pattern under the trees. Although all of these methods can provide useful data, they are all time-consuming, which makes it difficult to measure light interception in large areas of the orchard.
The authors have used the methods described by Grossman and DeJong (1998) to collect PAR interception data using a hand light bar (unpublished). However, the area covered by the hand light bar is small. Since both almonds and walnuts are mechanically harvested, it is difficult to cover large enough areas with the hand light bar to coincide with areas harvested. Therefore, the areas covered with the light bar and harvest data were often not equal.
The mobile platform described here was designed to automate the collection of canopy PAR data. This allowed much larger scale mapping of variability in orchard light interception and better comparison with mechanically harvested yield data.
Danyluk, M.D., Nozawa-Inoue, M., Hristova, K.R., Scow, K.M., Lampinen, B. & Harris, L.J. 2008 Survival and growth of Salmonella Enteritidis PT 30 in almond orchard soils J. Appl. Microbiol. 104 1391 1399
Giuliani, R., Magnanini, E., Fragassa, C. & Nerozzi, F. 2000 Ground monitoring the light-shadow windows of a tree canopy to yield canopy light interception and morphological traits Plant Cell Environ. 23 783 796
Grossman, Y.L. & DeJong, T.M. 1998 Training and pruning system effects on vegetative growth potential, light interception and cropping efficiency in peach trees J. Amer. Soc. Hort. Sci. 123 1058 1064
McFadyen, L.M., Morris, S.G., Oldham, M.A., Huett, D.O., Meyers, N.M., Wood, J. & McConchie, C.A. 2004 The relationship between orchard crowding, light interception, and productivity in macadamia Aust. J. Agr. Res. 55 1029 1038
Robinson, T.L. & Lakso, A.N. 1991 Light interception, yield and fruit quality of ‘Empire’ and ‘Delicious’ apple trees grown in four orchard systems Acta Hort. 243 175 184
Verheij, E.W.M. & Verwer, F.L.J.A.W. 1973 Light studies in a spacing trial with apple on a dwarfing and semi-dwarfing rootstock Sci. Hort. 1 25 42
Wagenmakers, P.S. & Callesen, O. 1995 Light distribution in apple orchard systems in relation to production and fruit quality J. Hort. Sci. 70 935 948
Wunsche, J.N., Lakso, A.N. & Robinson, T.L. 1995 Comparison of four methods for estimating total light interception by apple trees of varying forms HortScience 30 272 276