Crop load management of newly planted Pinot gris grown in warm climate of California

Abstract

Context and purpose of the study – San Joaquin Valley accounts for 68% of Pinot gris acreage and produces 83% of Pinot gris wine in California. Strong demand for Pinot gris has prompted growers to restrict the nonbearing period to less than two years, if possible. This requires permanent vine structure establishment the first year with a crop expected in the second year. Precocious cropping raises the risk of overcropping with possible carry-over effects in subsequent years. To identify the optimum crop level and economic threshold for newly planted Pinot gris vines, a field trial was initiated in a commercial vineyard in 2016.  

Materials and methods – Bench grafted Pinot gris vines with Freedom rootstocks were planted in February of 2015. Quadrilateral cordons were established in the same year aiming for the first crop in 2016. Randomized complete block design was set up with four levels of inflorescence thinning in the spring of 2016, and each treatment was replicated in 5 times. Inflorescences were hand thinned approximately 3 weeks pre-bloom. No thinning was applied after 2016, but data were still collected to study the potential carry-over effect in 2017 and 2018. Four treatments included: 1) all fruit removed (0 cluster per shoot); 2) one cluster per two shoots; 3) one cluster per shoot; 4) no fruit removed. Five vines in each block were labeled as data vines and yield components, pruning weight and fruit chemistry were collected in 2016, 2017 and 2018.  

Results – inflorescence removal increased fruit set, average berry weight, and soluble solids in 2016. Increased cluster compaction on thinned vines did not cause excessive bunch rot, but did partially compensate for the potential yield loss associated with inflorescence removal. Yield in 2016 was reduced by 6%, 28% and 100% with the severity of inflorescence removal. No thinning was performed in 2017 and 2018, but yield, fruit chemistry, and pruning weight were still measured. The Ravaz Index (RI) from treatment of one inflorescence per two shoots was 8.3 in 2016 and vines in that treatment had the highest accumulated yield across 2016 and 2017. Vines with RI > 12 showed significant delayed sugar accumulation in 2016 and reduced yields in 2017. Thus, newly planted vines with an RI> 12 in their first crop year were overcropped and will likely see reduced yields the following year, whereas vines with RI of approximate 10 provide maximum yield without affecting fruit chemistry and the following year’s crop. In 2018, yield and fruit chemistry were monitored as well, however no difference has been found across various treatments.