Alpha-acid Content Research Articles

Effects of Paraquat and Dinoseb in Hops

Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) at 1.1 and 2.2 kg/ha and paraquat + dinoseb (2-sec-butyl-4,6-dinitrophenol) at 1.1 + 0.7 kg/ha controlled redroot pigweed(Amaranthus retroflexusL.) and barnyardgrass [Echinochloa crus-galli(L.) Beauv.] in hops (Humulus lupulusL. ‘Yakima Cluster’) without reducing hop yield or the alpha and beta acid content of the hop cones. Three applications at about 3-week intervals were required to control weeds until harvest. Two applications controlled hop sucker growth. Paraquat at more than 0.6 kg/ha in the third application caused excessive reduction in hop sucker growth.

Late Applications of Hormone Mixtures to Increase the Yield of Seedless Hops (Humulus LupulusL.)

SummaryThe use of gibberellic acid (GA3) before flowering has been shown to increase the yield of some hop cultivars by increasing cone numbers. This work describes the effects of late application of hormone mixtures to hops after flowering, when increases in cone size have been obtained without a reduction in alpha-acid content. Both the physiological and practical implications are discussed.

The influence of temperature and sunshine on the alpha-acid content of hops

Analysis of trials carried out by the European Brewery Convention during 1968–1972 in 6 countries on 4 varieties of hop (Fuggle, Northern Brewer, Hallertau and Saaz) shows that the mean temperature and mean duration of sunshine between the date of coming into hop and the date of picking are the critical meteorological factors affecting the alpha-acid content. There is an optimum temperature for each variety lying between 16° and 17°C; below this optimum quality decreases rapidly with temperature, but above the optimum there is a slower decrease in quality with increasing temperature and some indication that increasing sunshine is the more significant factor.

Phosphorus Fertilization of Hops1

AbstractHops were grown on field plots treated with five levels of phosphorus fertilization to determine the effect of P on vine growth, cone quality, and zinc nutrition. A maximum P treatment of 1,344 kg/ha, applied over a 5‐year period, increased the extractable P level of the surface 20 cm of soil from 10 ppm to approximately 100 ppm. The P level in leaves and cones from this treatment was increased by approximately 0.10 to 0.15% P as compared with the no‐P treatment. Increased levels of P had no observable effect on vine color and vigor or on total growth as determined by vine green weight. The critical level for P in sidearm leaves at early bloom was indicated to be below 0.25%.The alpha acid content of cones decreased where P fertilization exceeded approximately 500 kg/ha. However, this decrease was poorly correlated with the P content of leaves, indicating the lack of a direct causal relationship.The P treatments caused a definite reduction in the Zn concentration in leaf and cone tissues, but did not induce observable Zn deficiency symptoms.