Mineral nutritional factors associated with alternate-bearing in American grapevines.

摘要

New York viticulture is challenged by the problem of irregular yields, particularly in American grape (Vitis spp.) vineyards. On the whole state basis, alternation of crops is minimal, but individual vineyards can have “off” year yields as low as 20–30% of “on” (high-yield) years. The “on” year diminishes fruit quality and delays maturation.; The main objective of this study was to focus on the effects of pruning, previous year defoliation and over-cropping on the allocation of mineral nutrients within the grapevine. Concord and Elvira varieties were selected as subjects.; Minimal pruning induced over-cropping and increased mineral losses from harvested fruit, but maximized yields, increased woody biomass structure, accelerated canopy development, minimized ‘prunings’ nutrient export and increased the leaf to stem ratio. Severe hand pruning enhanced root growth, minimized nutrient losses via fruit-harvest, reduced yield, reduced woody biomass reserves, slowed canopy development, and reduced leaves to stems ratios.; The effects of previous year stresses were studied. Early defoliation had a larger impact during the subsequent resting period, but it effects tended to dissipate by the following season pre-bloom stage of development. Early defoliation and heavy cropping had additive effects. Over-cropping effects during the resting period were hardly noticed, but were clearly evident at pre-bloom, also resulting in increased Ca concentration in the vines. Over-cropping reduced the following season whole vine uptake of nitrogen, phosphorus, potassium, calcium and boron from the resting season until pre-bloom. The capacity of roots and trunks to store and to make available nutrient for the developing canopy is addressed for nitrogen, phosphorus, potassium, calcium, magnesium, boron, and zinc.; Previous year defoliation and pruning negatively affected allocation of resources into reproductive organs. Less stressed vines tended to show more stable nutrient concentration. Fruit set was not consistently correlated with reproductive parameters. Number of cluster/vine was the reproductive parameter most consistently associated with yield. Correlations of reproductive factors with nutrient status of previous year early complete defoliation and previous year crop removal were affected by pruning. Boron was consistently correlated with number of clusters/vine and yields.