Optimizing crop water productivity and altering root distribution of Chardonnay grapevine (Vitis vinifera L.) in a silt loam soil through direct root-zone deficit irrigation.

The potential for sustaining grape production and improving crop water productivity in semi-arid areas through direct root-zone irrigation (DRZ) has been demonstrated in recent studies; however, it has only been tested for red wine grapes in sandy soils. To expand its application, a field study was conducted to investigate the influences of DRZ with reduced irrigation rate on yield, berry quality, root growth, plant water status and crop water productivity of white wine grape Vitis vinifera L. cv. Chardonnay grown in a silt loam soil within a semi-arid region of Washington state, USA. Compared with the surface drip irrigation which has been applied for decades in the study area, DRZ could improve the crop water productivity by 23 – 34 % and reduce the irrigation amount by 16 – 23 % without yield loss under variable weather conditions, indicating the efficacy of the DRZ as a novel subsurface irrigation strategy. Concurrently, DRZ restricted root distribution within 0 – 60 cm soil layers, and significantly reduced root number and root length density were observed in 20 – 40 cm soil depth. Moreover, grapevines under moderate water stress induced by DRZ accumulated more soluble sugar (8.8 % increase in °Brix on average) and yeast assimilable nitrogen (24.4 % increase on average) in berries. We conclude that proper deficit irrigation applied through DRZ would be applicable to optimize the water use for production and efficiently alter the root distribution pattern of Chardonnay grapevine cultivated in moderately permeable soils with improved berry quality. • Direct root-zone irrigation (DRZ) was compared with surface drip irrigation in Chardonnay vineyards. • DRZ strategy enhanced crop water productivity with minor effects on yield. • DRZ significantly restricted root growth in the 20–40 cm soil layer. • Total soluble solids and yeast assimilable nitrogen in berries were increased under DRZ. [ABSTRACT FROM AUTHOR]