Greenhouse grapevine transpiration and water use efficiency under different water and nitrogen conditions*

Determining the proper amount of water and nitrogen is important for obtaining reliable information on agricultural production management. This study investigated the effects of water and nitrogen (N) on greenhouse grapevine sap flow, photosynthetic parameters and leaf water use efficiency (WUEi) under three N applications (N1, 114.56 kg ha(-1); N2, 159.99 kg ha(-1); and N3, 240.00 kg ha(-1)) and three irrigation levels (W1, W2 and W3 representing the irrigating lower limits of 55% +/- 2%, 65% +/- 2% and 80% +/- 2% of the field capacity, respectively). The results indicated that sap flow decreased as N increased under the W1 treatment. However, sap flow increased as N concentration increased under W2 and W3 conditions. Photosynthetically active radiation (PAR) was the main meteorological factor controlling sap flow, with R-2 values ranging from 0.857 to 0.928. With the increase in N, the net photosynthetic rate (P-n) increased under the W3 condition. N application enhanced the promotion of WUEi by the W1 and W2 treatments. This study proposes the prospect of implementing an integrated management of water and N for grapevine growth in greenhouses, thereby promoting transpiration and water use efficiency in a scientific way.