Hop dry matter yield and cone quality responses to amino acid and potassium-rich foliar spray applications

Abstract

The use of amino acid and K-rich foliar sprays was evaluated in a commercial hop field in North-eastern Portugal. Four applications of an amino acid-rich foliar spray were performed in place of a second side dress N application of ~70 kg N ha À1 , which is usually applied by the farmer. The K-rich foliar spray was applied once at the cone developing stage as a supplement to the farmer's fertilization plan. The amino acid-enriched foliar spray maintained crop dry matter yield at the levels of the control treatment and increased cone alpha-acids concentration (41.8% in 2018 and 9.3% in 2019). Foliar K did not increase cone dry matter yield, cone size or bitter acid concentration. Tissue K concentration was not significantly affected by foliar treatments whereas the application of K seemed to increase N uptake, with leaves and stems being the predominant allocation tissues. Both foliar treatments increased leaf and stem Mg concentrations. The results seem to emphasize the importance of amino acids in the biosynthesis of bitter acids, while K and Zn seemed to play an important secondary role, maybe related to N metabolism and its reduction into amino acids. The concentrations of total phenols in cones and leaves were lower in the foliar treatments in comparison to the control, and the higher values registered in leaves. In this study, the use of amino acids as a foliar spray provided an interesting result, since they maintained cone dry matter yield and increased cone bitter acid concentration with reduced N use.

Large Chestnut Trees Did Not Respond to Annual Fertiliser Applications, Requiring a Long-Term Approach to Establishing Effective Fertilisation Plans

“…Leaf K concentrations varied greatly over the years and between treatments, although they generally remained within the sufficiency range. This pattern of K is common in shrub and tree species [13,21,38,48] and may be due to source/sink relationships and/or environmental constraints. Growing fruits are a primary sink for available K, the nutrient being remobilized from leaves [33].…”

“…Additionally in the fruits, B concentrations were the highest in the YA13:11:21 treatment, in particular, in the shell. Boron is very important in dicots, where it plays an important role in cell wall and membrane integrity, with these plants requiring greater amounts of B than monocots [48][49][50]. In the region, dicots often respond to the application of B [12,41,51].…”

Chemical constituents and bioactivities of hops (Humulus lupulus L.) and their effects on beer‐related microorganisms

“…Flavanol dimers Flavanol dimers linked through a methylene bridge and related unsymmetrical diaromatic methylene have been recently described as natural substances from Glycosmis montana, Agrimonia pilosa or produced by fermentation of cacao liquor (Boyer & Ducrot, 2005) Oligomeric flavanols Flavanols are biologically active molecules that have a wide range of effects and are known as very strong antioxidants that can scavenge various forms of free radicals (Fernandes et al, 2012) Polymers(tannins) Tannins are universally present in plants and represent the fourth most abundant group of secondary metabolites after cellulose, hemicellulose and lignins (Sharma, 2019) Phenolic carboxylic acids Ferulic Acid Ferulic acid (FA) is a type of aromatic acid compound that mainly exists in the cell walls of grass, plants, nuts, etc. During wine making and beer brewing, these phenolic acids can be released from the grape and malt into the juice and wort respectively (Xu et al, 2020) Other polyphenols Prenylflavanoids Prenylflavanoids are present in human fluids (plasma and urine) mainly as glucuronidated and sulphated metabolites (Quifer-Rada et al, 2017) Multifidol glucosides co-, ad-, n-and co-iso-multifidol glucosides, which are phloroglucinol derivatives with prenyl side chains, have been found in hops (Stevens et al, 1998;Chadwick et al, 2004;Stevens et al, 2002;Taylor et al, 2003) Resveratrol Resveratrol is a phytoalexin produced by a variety of plants in response to stress, injury or fungal infection (Jerkovic & Collin, 2007) (Afonso et al, 2021). The αacids isomerized to iso-αacids under high temperature conditions.…”

“…The α‐ and β‐acids represent a great portion of the dry constituents of hop cones and they are associated with flavour and bitterness of beer, besides playing an important role in plant properties, including antimicrobial potential (Afonso et al, 2021). The α‐acids isomerized to iso‐α‐acids under high temperature conditions.…”

Nitrogen Fixation and Growth of Potted Olive Plants through Foliar Application of a Nitrogen-Fixing Microorganism

“…Currently, in agricultural systems with high agricultural intensification, an increasing number of producers use plant biostimulants, mainly those that can be applied as foliar sprays, such as seaweed extracts and amino acids [18]. Plant biostimulants can be products of a very different nature, currently also including those that contain beneficial microorganisms [19].…”