Effects of Pruning Mulch on Nutrient Concentration of Avocado (Persea americana Mill.) Fruit under Subtropical Conditions

In this study, avocados of the Hass variety cultivated in Almunecar (Granada, Spain) are analyzed after soil mulching with pruning debris. The mulch treatment assay was composed of pruning wastes from subtropical crops (avocado, cherimoya, and mango) and garden wastes from the surrounding areas. The aim of this work is to analyze the nutrient content in avocado fruit and the effect of pruning-waste mulching on fruit development over four years. Avocado fruits collected in 2013, 2016, and 2017 were weighed, their volume and their sugar content were calculated, and macro- and micronutrients were analyzed in the peel, pulp, and stone (endocarp and seed). The pulp contained the highest concentration of nutrients, especially Cu, Zn, P, Na, and Ca. The peel presented high concentrations of Mn, K, and N, while the stone recorded the lowest values in nutrients, with the greatest decreases in years with the lowest precipitations registered. Over the study period, a decline was detected in the nutrient concentrations related to the alternation of high and low yields, typical of this crop, due to environmental factors. In the years 2016 and 2017, avocados accumulated higher amounts of micronutrients and P, presumably because of greater water availability in the soil. During the study period, the application of pruning wastes did not affect the nutrient concentration of fruits except for the garden pruning waste in certain elements in the pulp during the last study year.