Effects Of Planting Density And Branching Promoting Technologies On Growth And Development Of Apple Nursery Trees

The Apple (Malus domestica Borth) cultivar 'Fuji Nagafu No.2' was used to study theeffects of designed planting densities (50.0,20.0,16.7,14.3,10.0,8.3,7.1,6.7,6.3,5.6and4.8plants/m2) and several branching promoting measures (foliar spraying treatments of6-benzylaminopurine (6-BA) and equal mixture of6-BA and gibberellin (GA4+7), leafremoving, pinching and bud notching) on the growth of apple nursery trees. Experimentalresults showed (1) the period from mid-June to mid-Sept. was critical for apple nursery plantgrowth and final nursery quality grading in the treatments with the designed planting densities.Exactly in this period the influence of planting density on morphological parameters gotremarkable.(2) With decreasing planting densities, the growth indices including plant height,diameter of cultivar trunk, leaf weight, bud weight, single leaf area, total leaf area and totaldry weight exhibited an overall trend of increasing.(3) The growth indices of the plants with10.0-7.1plants/m2planting density were significantly higher than those with higher(16.7-50.0plants/m2) planting densities, and were slightly lower, even at the same levelstatistically, than those with lower (6.7-4.8plants/m2) planting densities.(4) When each treewas treated with the same amount of fertilizer,10.0plants/m2was the inflection point of thevariation tendency of total nonstructural carbohydrate (TNC) contents which declined firstand then increased gradually along with planting densities decreasing. Total nitrogen (N)content experienced rapid increment in treatments with planting densities from50.0to16.7plants/m2, but kept relatively stable in treatments with planting densities from14.3to4.8plants/m2. In terms of both plant morphological indices and nutrient status,10.0plants/m2wasthe highest planting density that met the requirement of important morphological parametersand could still have potential to get improvement in nutrition status through other measures.Also considering the economic efficiency of both land use and investment, we proposed that10.0plants/m2(row spacing of50cm, planting distance of20cm) is the most rationalplanting density for apple nursery stock production in the Loess Plateau of China.In addition, The results of several branching promoting measures treatments conductedaccording to the growth status of apple nursery trees, showed (1) spraying treatments of6-BAand the equal mixture of6-BA and GA4+7were effective for improving plant branchingsituation. When applying same concentration the mixture treatment's effect was better than 6-BA alone and the most appropriate concentration was1500mg/L.(2) Leaf removing andbud notching could not make nursery trees produce any lateral branches; though pinchingtreatment could produce a small number of long shoots, it could not meet requirementbecause of the narrow branching angle of new-produced shoots and week new-build leader ofthe whole plant.(3) The spraying treatments combining leaf removing with6-BA or themixture spraying gained better effect than6-BA or the equal mixture of6-BA and GA4+7spraying alone when applying lower spraying concentrations (500mg/L); but thisimprovement could not be obtained when applying higher spraying concentrations(1000-2000mg/L). According to the experiment results, the equal mixture of6-BA and GA4+7sparyingtreatment with concentration of1500mg/L is proposed to gain apple nursery with wellbranching situation.