Evaluation of photosynthetic efficiency and labor cost in cultivation of grape with an “oblique single cordon along ditch” trellis type in northern China

Abstract:【Objective】Grape cultivation is concentrated in the northern regions in China. Grape vine mustbe buried under the soil to cross the winter, which takes large amount of labor. However, the rising laborcost has turned out to be an important burden in grape production. The key to sustainable development ofgrape industry is to develop a simplified management with mechanized operations, which have become theurgent demand in modern grape production. There are many disadvantages in the traditional single cordongrape training system in northern China, such as high labor demanding and difficulty in machine opera-tions. In this study, a modified single cordon trellis type, the“oblique single cordon along ditch”was eval-uated in northern China, with focus on reducing labor demand in vine management so as to put forward asimplified management system and to promote the use of machinery in grape cultivation.【Methods】‘Redglobe'‘Flame Seedless' and‘Crimson Seedless' were used as the experimental materials in this studycarried out from 2011—2015. The“oblique single cordon along ditch”trellis system was compared withthe traditional single cordon system in terms of management efficiency and potential of machinery opera-tion as well as photosynthetic efficiency. Leaf area index was measured and the summer pruning efficiency was evaluated. The characteristics of tree light interception in the two trellis systems were analyzed using geometric dynamics, and the actual light interception area and length of the canopy in the two trellis sysems were compared. Canopy characteristics were analyzed with a CI 110 digital canopy structure analyzer of CID Bio-Science, Inc. and measurements of photosynthesis were carried out using a TPS-2 plant photosynthesis system. The Gauss model, right angle hyperbolic correction model and the Freundlich model were used to analyze and calculate the correlation parameters. The number of yellow leaves was recorded weekly from July 10 to September 4, to observe the changes in leaf senescence. Time cost for each pruning was also recorded. Before fruit matured, the distances from the ground to the trellis surface and the fruit were measured in order to analyze trellis surface sinking level during berry hanging time in the 2 trellis types.【Results】The area covered by leaves and light interception coefficient in two types of trellis were the same, but because the distribution of leaf surface was different from sunrise to sunset, the angle of sunlight intercepted was different, and the actual light interception area in the“oblique single cordon along the ditch”was greater than the traditional single cordon trellis system. The minimum net photosynthetic rate and the diurnal peak value of net photosynthetic rate in the“oblique single cordon along the ditch”trellis system were greater than traditional single cordon system. The integral area of the curve representing the accumulation of photosynthetic products in the“oblique single cordon along the ditch”trellis system was greater than the traditional control. The range of light intensity for net photosynthesis in the former was 1 942 and 1 795 μmol·m^-2·s^-1, while in the traditional single cordon trellis system was 1 830 and1 730 μmol·m^-2·s^-1 in‘Red Globle'and‘Flame Seedless', respectively. Leaf area index in the“oblique single cordon along the ditch”trellis system was lower than the traditional control. On August 15, leaf area index of‘Red Globe'in the former was 3.1, while it was 4.0 in the latter. In case of‘Flame Seedless', leaf index was 3.1 and 4.0 in the“oblique single cordon along the ditch”and the traditional trellis systems, respectively. The process of leaf yellowing in the“oblique single cordon along the ditch”trellis system was50% slower than in the traditional system. The time cost for pruning in the“oblique single cordon along the ditch”trellis system was 4.35 h per 666.7 m² and 16.39 h per 666.7 m² in the traditional control. Before fruit matured, trellis frame sinking was serious with the lowest place being 1.44 m above the group in the traditional single cordon system, while in the“oblique single cordon along the ditch”trellis system, the trellis frame sink was not obvious with the lowest point being 1.62 m above the ground.【Conclusion】Compared with the traditional single cordon trellis system, the“oblique single cordon along the ditch”trellis system has the advantages of high photosynthetic capacity and light utilization efficiency. It also reduces the labor intensity for summer pruning. In addition, the sinking of the trellis frame is not obvious. The fruit clusters are in lines, which is convenient for management and has potential for mechanization.