title: Empiric mathematical model for predicting the content of alpha-acids in hop (Humulus lupulus L.) cv. Aurora.
abstract: The aim of this research is to find a simple mathematical model due to sum of effective temperatures and rainfalls from second germination after spring pruning till the technological maturity of hop cones, in order to achieve reliable prognosis of alpha-acids content in hop cv. Aurora. After mathematical analyses of experimental data by Eurequa Formulize 0.96 Beta software 17 equations were offered, and after substituting the values of dependent and independent variables in all equations only one equation was chosen with p = 0.034 (p<0.05). This equation is not reliable in extremely drought year if crop evapotranspiration ET0 in July is higher than 4.5, primarily because of negative influence on formation and development of hop glandular trichomes. Considering achieved results it is possible to suggest following general equation for alpha-acids accumulation in hop: y = [(k 1 w) - k 2 - (k 3 w (2))/x] ÷ (-10) ↔ ET 0 July  ≤ 4.5. Where y is alpha acids content in dry matter (%), x = sum of effective temperatures and w = sum of rainfals, both from second germination after spring pruning till technological maturity of hop cones. Coefficients k 1 , k 2 and k 3 are determined for cultivar Aurora (53.8, 453 and 1.33, respectively).
authors.affiliation: Križevci College of Agriculture, M. Demerca 1, HR-48260 Križevci, Croatia.
authors.forename: Siniša
authors.initials: S
authors.lastname: Srečec
authors.forename: Barbara
authors.initials: B
authors.lastname: Ceh
authors.forename: Tanja Savić
authors.initials: TS
authors.lastname: Ciler
authors.forename: Alenka Ferlež
authors.initials: AF
authors.lastname: Rus
keywords: Accumulation of alpha-acids; Alpha-acids; Empiric mathematical model; Eurequa software; Hop; Humulus lupulus L