Efficient sampling to determine the distribution of fruit quality and yield in a commercial apple orchard

In situ assessment of fruit quality and yield can provide critical data for marketing and for logistical planning of the harvest, as well as for site-specific management. Our objective was to develop and validate efficient field sampling procedures for this purpose. We used the previously reported 'fractionator' tree sampling procedure and supporting handheld software (Gardi et al., 2007; Wulfsohn et al., 2012) to obtain representative samples of fruit from a 7.6-ha apple orchard (Malus ×domestica 'Fuji Raku Raku') in central Chile. The resulting sample consisted of 70 fruit on 56 branch segments distributed across 36 trees for yield estimation. A sub-sample of 56 fruit (one per branch segment) was removed; and, individual fruit mass, firmness and contents of malic acid, soluble solids and starch were measured in the laboratory. The data also were used to obtain an imprecise, but unbiased, estimate of yield. Estimated marketable yield was 295.8±50.2 t. Field and packinghouse records indicated that of 348.2 t sent to packing (52.4 t or 15% higher than our estimate), 263.0 t was packed for export (32.8 t less or -12% error compared to our estimate). The estimated distribution of caliber compared very well with packinghouse records. The distributions of sample fruit maturity measurements were used to estimate the proportion of fruit meeting exporter quality standards.