The Effect of Different Organic Foliar Fertilization on Physiological and Chemical Characters in Hop (Humulus lupulus L., cv Cascade) Leaves and Cones

Margherita Rodolfi,Tommaso Ganino,Lorenzo Barbanti,Riccardo Casolari,Luca Pretti,Deborah Beghé,Cristiana Giordano,Raffaella Petruccelli,Andrea Fabbri,Massimiliano Rinaldi

doi:10.3390/app11156778

Margherita Rodolfi, Tommaso Ganino + Show 8 more

Open Access

https://doi.org/10.3390/app11156778

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Abstract

Background: Hop cultivation requires an abundant quantity of nutrients to reach higher cone yield and quality. The aim of this work was the evaluation of different fertilization plans to obtain an improvement in product quality. Methods: Foliar analysis, anatomical analysis through the use of light microscope and SEM; physiological measurements through atLEAF, Handy PEA and spectrophotometry, were carried out to determine chlorophyll content, carotenoids and photosynthetic efficiency in two periods (t1, t2) for four experimental treatments and a Control (Treat 1, Treat 2, Treat 3, Treat 4, Untreat). Leaf texture (texture analyzer), color (colorimeter), DPPH activity (spectrophotometer), bitter acid content (HPLC-UV) and essential oil yields (steam distillation) and cone yields were measured. Results: Treat 2 showed the best performance: (i) in leaves, in terms of texture, chlorophyll content and color; (ii) in cones, with 6.98% of alpha acids, 1.78% of oil yield and 3.55 kg of fresh cones per plants. Conclusion: The fertilization plans caused alteration in micro and macro elements content in hop leaves and in the composition of hop cones. In our conditions, the best fertilization plan, in terms of cone productivity and quality, was Treat 2, highlighting the value of a customized organic foliar fertilization plan for hop cultivation.

Highlights

Hop, Humulus lupulus L., is a dioecious species whose female flowers are used as aromatizing and flavoring agents in beers, and in traditional medicine due to the presence of peculiar bioactive compounds
P in t1 reaches the highest amount in Treat 4, even if P was not applied, while in t2, P presence was in accordance with the fertilization plan, with the highest amount in Treat 3 which corresponds to the highest amount of phosphorous (P2O5) applied (Table 1)
Calcium is not present in any treatment; Untreat in t2 has the highest Ca content. This difference is probably due to an altered response for the absorption of Ca due to the interaction with the other elements; it is well known that some elements can promote or inhibit the absorption of others, as in the case of an excess of P that inhibits the absorption of elements like Zn, Cu, Mn and Ca [34,35]

Summary

Introduction

Humulus lupulus L., is a dioecious species whose female flowers are used as aromatizing and flavoring agents in beers, and in traditional medicine due to the presence of peculiar bioactive compounds. Nitrogen (N) is one of the most important macro-nutrients necessary for unconstrained growth of the hop plants. It can influence plant yield, quality and health. This nutrient has an important role in fruit size, flavor and composition [3,4]. Results: Treat 2 showed the best performance: (i) in leaves, in terms of texture, chlorophyll content and color; (ii) in cones, with 6.98% of alpha acids, 1.78% of oil yield and 3.55 kg of fresh cones per plants. The best fertilization plan, in terms of cone productivity and quality, was Treat 2, highlighting the value of a customized organic foliar fertilization plan for hop cultivation

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