The effect of increasing laid-down nodes on carbon and nitrogen resources of high yielding Sauvignon blanc vines

Abstract

A study was undertaken to quantify the importance of carbon and nitrogen reserves for sustained optimal growth and production of Sauvignon blanc grapes. The three-year replicated treatments consisted of two pruning treatments of four (48N) and six (72N) 12- node cane VSP-trained vines in Marlborough, New Zealand. Samples of root and trunk tissues were taken throughout the seasons for carbohydrate (CHO) and nitrogen (N) analyses, along with the collection of annual pruning and yield measurements. Both grape yield and vine pruning weights significantly increased only in the first year in which higher node number treatments were imposed. In the following years, higher node number treatment yields were not different, mainly because of the reduced bunch sizes and increased blind budding at 72 nodes. Changes in CHO and N reserves were found to be very dynamic during different stages of vine development. While little difference was found in CHO concentrations, increased node number decreased N concentration in the roots during the growing season and markedly diminished N build-up during the dormant period. The reduction in N concentration intensified with consecutive years of the treatment. The extra demands on the vine reserves by 72N were demonstrated in the subsequent season by reduced vine growth and yield. Generally, the reductions in trunk and root winter reserves were replenished during the next seasonal cycle of growth, which suggests that grapevine N and CHO partitioning favour the build-up of reserves in the permanent structure over increasing vine size and yield. However, after consecutive years of high node numbers, the cumulative effects of reduced N and CHO reserves and smaller, less fruitful canes from the previous year did reduce both yield and vegetative growth in the second and third growing seasons, to be equivalent to those of the 48-node vines. This work shows that the vine can overcome incidental reductions of vine CHO and N reserves, but repeated reduction of these reserves is manifested in reduced cane fruitfulness, yield and vegetative growth.