| Weibei Plateau was the largest high-quality apple (Malus domestica Borkh.) productive base in China and the world's at present, and most of the fruit orchard was in full productive stage or in final full productive stage. When apple tree in full productive stage or in final full productive stage, its reproductive growth was stronger than vegetative growth, and radial growth was stronger than centrifugal growth, but local farmers also pruned apple trees by light pruning or long-branch pruning, these caused the tree's growth weak, crown closure, fruit-setting position outside, fruit becoming smaller. In order to improve orchard air and light, increase the fruit quality and orchard economic output, Shaanxi province promoted"modifying tree forms", but it destroyed the growth balance between aboveground and underground, caused the rot(Valsa mali Migable et Yamada) flooded, and shortened full productive time, decreased orchard economic output. Renewal pruning could maintain crown structural integrity, maintain the balance between vegetative and reproductive growth, prolonged full productive time, but fewer farmers pruned apple trees by renewal pruning in recent years. This experiment completed at Changwu county in Weibei plateau, took 25 years old"Red Fuji"apples tree as test materials, and its stock was Xinjiang wild apple [Malus sieversii (Ldb.) Roem], monitored the effects of renewal pruning and long-branch pruning (control) on photosynthetic ability, the quality of fruit and yield, tree nutrition, canopy structure, soil moisture and growth of branches, leaves, fruit, and achieved the following results.1. The diurnal variation of photosynthetic rate and stomatal conductance of lateral shoot of bearing part, leafage shoot and vegetative shoot all showed bimodal curve, the diurnal variation of transpiration showed single curve, the diurnal variation of intercellular concentration showed anti-parabola curve. Renewal pruning significantly increased photosynthetic rate, stomatal conductance and transpiration of different shoots; and significantly decreased intercellular concentration.2. Renewal pruning significantly increased leaf area index and average foliar obliquity, slightly increased extinction coefficient, and significantly reduced canopy openness.3. Renewal pruning increased nitrogen, phosphorus, potassium, calcium contents in leaves, shoots, fruit and roots, and significantly increased nitrogen, phosphorus, potassium, calcium contents in shoots.4. The growth dynamic change of development shoot and bourse shoot of bearing part were single peak, and renewal pruning increased the length by 63.92% and 51.14% of development shoot and lateral shoot of bearing part compared to long-branch pruning, and their thickness increased by 20.93% and 9.76%. Renewal pruning significantly decreased total branch number, significantly decreased the number of short branch, leafage branch and flower bud branch, significantly increased the number of water branch, long-branch, and medium branch.5. Renewal pruning increased soil moisture in 0~240 cm depths, and had no significant effects below 240 cm soil layer from sprout stage to defoliation stage. The peak of soil evapotranspiration intersity of renewal pruning was higher and delayed 20 d than long-branch pruning, but the average intensity had no significant difference in growing period. Renewal pruning improved soil moisture.6. Renewal pruning significantly increased fruit yields, fruit weight, fruit shape index and the content of soluble sugar; and had no significant effect on fruit firmness, soluble solids, acid content, vitamin C. Vertical diameter and transverse diameter of fruit by renewal pruning increased 15.6% and 16.1% compared with long-branch pruning, and significantly higher than long-branch pruning.Renewal pruning increased photosynthetic rate of leaves, increased tree's nutrition, improve the canopy structure, increased soil moisture, and promote the growth of branches, leaves and fruit, increased fruit yield and economic output. |
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