Response of Hops to Algae-Based and Nutrient-Rich Foliar Sprays

Abstract

Over recent years, some hopyards of northeast Portugal have presented poorly developed plants and reduced productivity. In this study, an attempt was made to improve the homogeneity of hop fields and restore their productivity by using plant biostimulants as foliar sprays. The experimental apparatus included four field trials carried out in four plots of different plant vigour, as evaluated by farmers over previous years (weak, fair, good and very good). The experiments were arranged as a factorial of foliar treatment (two plant biostimulants containing extracts of seaweed algae and an untreated control) and year (2017 and 2018). The plot and the year influenced greatly almost all the measured variables related to tissue nutrient concentration and crop performance. In the control plots, cone dry matter (DM) yield varied from 83.3 to 394.4 g plant−1 from the weak to the very good plots. In 2018, cone DM yield was significantly higher than in 2017. The use of foliar sprays influenced less the elemental composition of plant tissue than the plot or the year. The use of foliar sprays only increased significantly crop yield in the plot of weak plant vigour. The foliar treatments did not increase α- and β-acid concentration in the cones; in the control treatment of the most productive plot, the values were, respectively, 11.2 and 3.9%. Although seaweed extracts tend to help plants cope with several abiotic and biotic stresses, they showed to be effective in mitigating the stress that is affecting these plants, which probably is poor soil drainage caused by the flooding irrigation system, only under conditions of severe stress.

Intercropped Maize and Cowpea Increased the Land Equivalent Ratio and Enhanced Crop Access to More Nitrogen and Phosphorus Compared to Cultivation as Sole Crops

“…The results suggest that N may have been a limiting factor for maize growth, a thesis supported by the significantly lower N concentration values in maize leaves compared to the sufficiency range for the species [32]. The concentration/dilution effect of a given nutrient in plant tissues occurs when, for a given soil nutrient availability, there is variation in DMY due to other agro-environmental variables unrelated to nutrient acquisition [40][41][42][43].…”

The Phenolic Composition of Hops (Humulus lupulus L.) Was Highly Influenced by Cultivar and Year and Little by Soil Liming or Foliar Spray Rich in Nutrients or Algae

“…It is also known that environmental variables can affect the secondary metabolism of plants and, therefore, the accumulation of phenolic compounds [35,36]. Although plant vigor had a marked effect on tissue nutrient concentration [24], its effect on total phenols in hop coves was reduced.…”

“…Furthermore, the relationship between total phenols and nutrient concentration in hop cones was evaluated through a principal component analysis (PCA) and correlation analysis. The results of the elemental composition of hop cones, already reported in previous studies [22][23][24], were used to evaluate their relationship with hop phenols. Data on dry matter (DM) yield and hop acids from these experiments have also been reported [21][22][23][24], but the relevant information to understand the accumulation of phenols in plants in response to the different factors of variation was discussed here.…”

“…The results of the elemental composition of hop cones, already reported in previous studies [22][23][24], were used to evaluate their relationship with hop phenols. Data on dry matter (DM) yield and hop acids from these experiments have also been reported [21][22][23][24], but the relevant information to understand the accumulation of phenols in plants in response to the different factors of variation was discussed here. In short, the ultimate objective of this research was to obtain useful data for both hop producers and the craft beer industry.…”