The foliage-light product, a measure for assessing orchard canopies, and its relation to the yields of three apple varieties trained to three forms.
The foliage-light product (FLP) is proposed as a simple and rapid means of assessing management systems of orchard trees by combining the two important production factors - foliage distribution and light environment. It is defined as the sum of the products of leaf weight and a mean light score determined for each cell of a grid taken through the canopy. The FLP was determined for each of 9 treatments of 3 tree forms applied to Golden Delicious, Red Jonathan and Granny Smith apple trees, chosen to give a wide range in canopy structure and yield. Canopies were sampled as slices across the hedgerow. Light intensities were measured with a selenium photocell and subsequently transformed into a light score zero below 2 mW/cm2, linear between 2 and 32 mW/cm2 and constant above 32 mW/cm2. Observations were made on 10 occasions, 6 of them under a clear sky. Data are presented on the distribution within the canopy slice of leaf weight, light score and FLP values. For each of these, canopy totals were influenced by treatment much more than by cv., whereas cv. had a considerable effect on distribution within the canopy. Averaged over the treatments, 18% of the slice was both well supplied with foliage and experienced high light scores; this 18% contributed 41% of the total FLP. Conversely, 37% of the slice, poorly foliaged and lit, contributed only 10% of the total FLP. Within each cv. total FLPs were linearly related to yields averaged over 3 years.