Effects of canopy characteristics on fruit yield and quality with different training systems in nectarines

Abstract: 【Objective】The traditional shape of peach tree is easy to make the crown clogging, and the light inside the canopy is not enough, thus reducing the fruit yield and quality. Meanwhile, the traditional planting mode occupies a large amount of land, which increases the planting cost and waste of land resources. Recent years one of the key changes in peach cultivation is the increasing of planting density.Based on the development of intensive production, new requirements are put forward for peach tree cultivation, and higher requirements are put forward for saving management labor in future. Therefore, it is the current research direction to train reasonable tree shape and formulate corresponding evaluation criteria to figure out the optimal tree shape and planting density for both better yield and quality. The amount of radiation intercepted by the canopy is closely related to the growth and development of plants. Tree shape evaluation mainly focuses the light canopy, which can provide scientific and reasonable theoretical basis and technical support for tree shape selection. Through the determination and analysis of canopy characteristics, the light energy utilization, fruit yield and quality with three planting densities were cpmpared, which were pillar system, Y system and three-limb-open center system. Studying on the tree shape and cultivation mode can be helpful to provide suitable reference for the development in high arid peach-produing area in Northwest China.【Methods】Correlations between the number and arrangement of the scaffold limbs, canopy structure, and fruit quality of'Longyou 1'nectarine with 3 training systems(Three-limb-open center system, Y system and pillar system) were investigated using CI-110 canopy analyzer by means of hemispherical image analysis. Three-limbopen-center system was at a planting space of 3 m × 5 m, with a trunk height of 60 cm and central angle at 120°; Y system was at a planting space of 2 m × 5 m, with a trunk height of 60 cm, and central angle at 45°; Pillar system was at a planting space of 1.2 m × 2.5 m, with trees being about 2.5 m high.【Results】The number of shoots of 4-6 years tree with Pillar system reached 10 400-12 000 per 666.7 m2, higher than the other two kinds of systems, and the observation for three years showed that shoot number with Pillar system was the highest per 666.7 m2. The 5-year-old pillar tree reached a stable shoot quantity. The leaf area index was significantly higher than the other two systems, but the direct light transmission coefficient was the lowest. The results also showed that the pillar tree could reach a higher shoot number within the shortest time, thus achieving the goal of early fruit harvest and early cost return. However, the fruit quality decreased due to the high planting density, and the soluble solid content, soluble sugar content and sugar-acid ratio were significantly lower than the other two systems. In the early fruiting stage(4 years old), the shoot volume per 666.7 m2 of the Y system was the lowest among the three systems, but the difference between the Y and the pillar systems decreased year by year after the fruiting stage(5 years old). The yield of Y system was higher than that of threelimb-open-center system, but the difference in fruit quality was not significant. The average leaf dip angle of Pillar tree was only 25.12°, which showed that the orchard was airtight and the high quality fruit rate was low. Y system and three-limbopen-center system had good fruit quality, indicating that the planting density was reasonable. The analysis of inter-row canopy characteristics between the leaf area index and average leaf angle difference was not significant. TCDP of Threelimb-open-center system in inter-row was significantly greater than Y system, probably due to that Threelimb-open-center system had two limbs on the north side, one limb in the south, causing better inter-row illumination, but Y system showed no significant difference in fruit quality, however, the yield per unit of Y system was significantly higher than three-limb-open-center system of 6 year-old trees.【Conclusion】In early fruit-bearing stage, the canopy structure with pillar system had the advantages of fast completion of training and high yield that can obtain earlier return,but the fruit qualitywas lower. The fruit quality of the Y system and three-limb-open-center system was better, but early productivity was lower, the yield of the Y system increased year by year after entering the fruiting stage. The Y system was a shape suitable for using in modern nectarine orchards.