Abstract
Abstract: Soil water content is the main factor affecting plant growth and dry matter accumulation. The study of grape fruit enlargement, fruit quality and yield under delayed cultivation facility in cold area is of important significance for fresh grape's balanced supply. A field experiment was conducted during the grape growing season in Zhang Ye, China in 2013 to investigate the influence of water stress in different growth stages on grape growth and yield under delayed cultivation facility. The growing season of delayed planting grapes was divided into five growth stages including germination, vining, flowering, fruit enlargement and colored mature. Three soil water treatment levels were designed in each growth stage by either drying or adding water to reach the designed soil water content (75%-100% field capacity, 65%-90% field capacity, and 55%-80% field capacity). Grape yield, quality and water efficiency were studied under above water regimes. The results showed that there were two distinct high and low peaks in delayed planting grapes enlargement cycle. The first enlargement peak appeared in the former 16 days of enlargement period, and the average horizontal and vertical enlargement rate reached 0.747 and 0.959 mm/d. The grapes' second transverses enlargement peak appeared in the first 44-52 days, the vertical diameter was postponed one week, and the average rate of inflation was only 0.134 mm/d, which was smaller than the transverse by 0.063 mm/d. There was significantly positive correlation between grape fruit's transverse diameter enlargement rate and longitudinal diameter enlargement rate at the same time except in fruit expanding period of 52-59 days, and the grape fruit transverse and longitudinal enlargement were strongly synchronous. In the early fruit enlargement stage, fruit enlargement rate showed evident re-watering compensation effects under the VS (moderate water stress in grape's vining stage) and FS (moderate water stress in flowering stage) treatments, and later the rate was slow again. Before July 30th (within 30 days of fruit enlargement stage) the processing of fruit growth rate of FS treatment has been at a high level, and the fruit cumulative transverse diameter and longitudinal diameter enlargement were up to 16.82 mm and 20.16 mm in this period, respectively, which reached 71.1% and 78.23% of the final grape fruit sizes. That meant fruit enlargement rate of early enlarging period determined the final grape fruit size, which must be paid attention to in the process of grape plant. Grape yield, water use efficiency (WUE), irrigation water use efficiency (IWUE) of GS (moderate water stress in germination stage) were higher than other treatments, and its value reached 36 333 kg/hm2, 7.69 kg/m3, 10.27 kg/m3, respectively; and CM treatment (mild stress in coloring maturity stage) ranked second. So from the yield, WUE and IWUE point of view, the best water treatment was carrying out moderate water stress in germination period (the minimum soil water content was 55% field capacity, upper limit was 80% field capacity), and the rest of the growth period carried out sufficient water supply (the minimum soil water content was 75%, upper limit was field capacity). Grapes soluble solids, VC, fructose, glucose, total sugar of CM treatment were 19.0%, 1.66 mg/50 mL, 9.64%, 13.46%, 24.76%, respectively, which were significantly higher than CK (P＜0.05). Therefore, with a comprehensive consideration of yield, WUE, IWUE and fruit quality indicators, the optimal water regulation treatment under delayed cultivation was CM, namely mild water stress (soil water content was 65% field capacity-90% field capacity) in ripe period, and sufficient water supply (soil water content was 75% field capacity-100% field capacity) in other periods. The research can provide valuble information for precise management of soil moisture in grape's growth period, and to achieve the purposes of water saving and grape quality and production improvement.
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