Patterns of Nutrient Accumulation in ‘Hass' Avocado Fruits

‘Hass’ avocado trees absorb nutrients in relation to key stages of tree phenology. An understanding of the tree’s seasonal nutrient requirements is critical for developing best management fertilizer practices. Nutrient analyses of developing ‘Hass’ avocado fruit collected monthly provided evidence that fruit accumulated all nutrients studied, except calcium (Ca), in a double sigmoid curve representing uptake during the summer and the following spring, with only limited accumulation during the winter months. The accumulation patterns, however, differed among nutrients. For example, nitrogen (N) and phosphorus (P) accumulation paralleled fruit dry matter accumulation, with about 50% of the total fruit N and P taken up by young fruit from mid-May through November and the remaining 50% taken up by mature fruit from April to July the following year. In contrast, approx. 30% of the total fruit potassium (K) concentration accumulated between mid-May to November, whereas the remaining 70% of fruit K accumulated the following year between April and July. Fruit Ca concentration followed a single sigmoid accumulation pattern, initiated at full bloom, proceeding over the next 5 months and then remaining static through legal maturity and harvest. The results were used to time fertilizer applications to coincide with periods of fruit nutrient demand to improve nutrient uptake and reduce the potential for groundwater pollution.