Influence of mineral fertilization (NPK) on the quality of apricot fruit (cv. Canino). The effect of the mode of nitrogen supply

Abstract

International audienceAbstract - The effects of different levels of nitrogen, phosphorus and potassium (NPK) fertilizers were evaluated on biochemical markers involved in the quality of apricots (sugars, organic acids and free acidity) and technological qualities (phenolic compounds: substrates of the enzymatic browning reaction). Apricot fruits (cv. Canino) were picked in the Marrakech area (Morocco). An experimental design was carried out with four factors: N, P and K, each one at two levels, and two modes of N supply. The weight of fruits, refractometric index and free acidity were measured in apricots at the commercial maturity stage. The main phenolic compounds, sugars and organic acids were identified and their concentrations were determined using high performance liquid chromatography (HPLC). Apricot fruits from trees fertilized with 80 kg N ha$^{-1}$ showed a significantly higher content in phenolic compounds, a slightly higher sugar concentration and a lower organic acid concentration than those fertilized with 150 kg N ha$^{-1}$. In this latter case, the weight of fruits was higher. In contrast, fertilization with the lowest K level (60 kg ha$^{-1}$) resulted in lower concentrations in phenolic compounds and sugar content when compared with the fruits which received the highest K level (120 kg ha$^{-1}$). Our results showed that P fertilization is not the main factor in the technological qualities of apricot fruits expressed as phenolic content. The mode of N supply seemed to play a major role in the quality of apricot fruits. The second application resulted in a higher accumulation of phenolic compounds and an increase in fruit weight, while the first application tended to stimulate the biosynthesis of organic acids. In addition, our results showed great interactions between N, P and K fertilization. The N-K interaction was found to be the most significant one for all the biochemical markers studied in this work.Influence de la fertilisation minérale (NPK) sur la qualité de l'Abricot (cv. Canino). Effet du mode de fractionnement d'azote. La qualité de l'abricot, destiné notamment à subir une transformation industrielle, est fortement liée à la teneur en certains composés tels les polyphénols, principaux marqueurs de notre étude, les sucres et les acides organiques. À cet effet l'objectif du présent travail consiste à étudier l'incidence de la fertilisation minérale sur l'évolution de ces réponses dites de qualité. Cette étude a été menée dans le verger expérimental de la Société de Développement Agricole situé au sud de Marrakech (Maroc). Un plan d'expériences avec quatre facteurs : azote, phosphore et potassium, chacun avec deux niveaux, et deux modes de fractionnement d'azote (avec 1/3 d'N au mois de février et 2/3 au mois d'avril ou 2/3 d'N au mois de février et 1/3 au mois d'avril) a été mis en place. Le poids moyen du fruit, l'indice réfractométrique et l'acidité libre ont été mesurés dans les abricots récoltés à maturité commerciale. De même, les composés phénoliques, les sucres et acides organiq...

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