Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2006
Publication Date: 12/1/2006
Citation: Dragoni, D., Lakso, A.N., Piccioni, R.M., Tarara, J.M. 2006. Transpiration of grapevines in the humid northeastern United States. American Journal of Enology and Viticulture. 57(4):460-467. Interpretive Summary: Irrigation management is a critical farming practice even in rainfed areas like upstate New York, where short-term drought during the growing season is not uncommon. Irregular or unpredicatble summer rains can compromise either the yield or the quality of a crop, including grapes. Optimal application of supplemental water by irrgation depends upon the availability of good data on the water needs of the crop and on local evaporative demand. While data of this sort are generally available in the arid western US, where irrigation is common, such data may be unavailable or in less applicable format in more humid areas like the northeastern US. The study documented by this report included direct measurements of the water being used (transpired) by 'Concord' juice grapes in New York state, and showed that grapevines in that environment can suffer from short-term drought during the summer. Measurements of actual water use by these grapevines were compared with values predicted by a common model that incorporates local evaporative demand. This common model has been shown to work fairly well in arid climates and for many agronomic crops, but it appears to be less appropriate for tall and discontinuous crops like orchards and vineyards. For best management of irrigation water in more humid climates, it will be necessary to develop crop-specific models that incorporate data from the local environment.
Technical Abstract: For irrigation design and scheduling, water use of crops is commonly estimated from grass reference evapotranspiration (ET0) estimates multiplied by published crop coefficients (kc). This method is assumed to stabilize kc in different climates due to the response of ET0 to differing climates. However, the simple application of kc may not be accurate in cool, humid climate, especially for sparse and tall crops that are well coupled to bulk air. The aim of this work was to measure actual transpiration in a vineyard in New York State, and to test the reliability of the reference-grass-based crop coefficient model. Measurements of water use in Concord grapevines (Vitis labruscana Bailey) were made with heat balance sap flow gauges, calibrated with canopy gas exchange chambers. Daily ET0 was estimated from meteorological data acquired by a nearby station. Daily transpiration rates per single vine ranged between 15 and 40 liters per hour, with hourly rate peaks of 4 liters. Water use from vines declined during the hottest and driest part of the season, probably due to either water or heat stress. This suggested that even in humid climates, grapevines might occasionally require irrigation. The reference-grass-base crop coefficient model was limited by its inability to account for the degree of coupling between transpiration regulation and bulk air conditions, in particular the vapor pressure deficit. Overall, the results suggest the necessity of developing crop-specific models for water use management.