Mechanical Canopy and Crop-Load Management of Pinot gris in a Warm Climate

Abstract

The interactive effects of mechanical canopy management on the optimum cropping level and Ravaz index of Pinot gris in a warm growing region were determined. The study examined two pruning methods, three shoot thinning treatments, and two leaf removal treatments arranged factorially in a randomized complete block design with four replications. The pruning methods were applied by either hand pruning to 23 nodes/m or mechanically hedging and retaining a 100 mm spur height. The shoot thinning treatments were applied mechanically at modified E-L stage 17 to retain 23 (low), 33 (medium), or 45 (high, not thinned) shoots/m of row. The leaf removal treatments removed leaves on the east side of the canopy in a 450 mm zone in the fruiting zone, 20 days postbloom with a mechanical deleafer or no leaf removal was done. The interaction of mechanical hedging and medium shoot thinning treatments reduced the contribution of noncount shoots to total shoots. Percent canopy gaps and photosynthetically active radiation increased, while canopy leaf layers decreased with the application of leaf removal regardless of pruning or shoot thinning regime in both years. Yield increased and berry and cluster weight decreased in both years with the application of mechanical hedging and medium shoot thinning compared to hand-pruned vines without any detrimental effects on fruit composition. To achieve the economic crop level threshold of 8.15 kg/m, a Ravaz index of 10.2 to 12.0 kg/kg was needed. This Ravaz index corresponded to a pruning weight of 0.82 to 0.92 kg/m. The study identified a mechanical hedging and shoot thinning method where a 100 mm spur height was retained during the dormant season and 35 shoots/m of row was retained at E-L stage 17 to optimize crop load without adversely affecting pruning weight or fruit composition in a warm climate. The identified method provided 79% labor operations cost savings compared to hand pruning alone.