The Effect of Concord Vineyard Microclimate on Yield. I. The Effects of Pruning, Training, and Shoot Positioning on Radiation Microclimate

Abstract

The effect of pruning severity (3-51 nodes retained per meter of row), training method (Hudson River Umbrella or Geneva Double Curtain), and shoot positioning on the radiation microclimate of Concord grapevines was investigated at Hector, New York. Basal leaf illuminance was improved early in the season by canopy division and low shoot density; after flowering, the major effect was of shoot positioning. Generally, the light climate of individual leaves changed with growth of the vine during the season, but was most consistent for undivided canopies of high shoot density and after shoot positioning.

Typically, there was poor correlation of illuminance between adjacent individual leaves on a shoot, an expression of the ability of individual leaves to optimize their radiation microclimate. Axillary buds showed a reduced range of illuminance compared to the subtending leaves. Measurements of leaf aspect and inclination showed a preference for angle of about 45° to the horizon and to face the region of maximum illuminance — that is, the inter-row area.

Leaves in the canopy interior receive levels of photosynthetically active radiation (PAR) up to 1/100 of that of exterior leaves, and the proportion of 660 nm/730 nm radiation is also decreased to 1/10. Exterior leaves experience a relatively constant 660 nm/730 nm ratio independent of cloud cover, but PAR levels may drop to less than 50% with cloud cover.