R. Kalaydzhieva, D. Davidov, A. Matev*, V. Kuneva
Department of Melioration and Geodesy, Faculty of Viticulture and Horticulture, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria
Abstract. The aim of the study is to establish the parameters of the relationship “Yield – ET” for green beans on the base of the growth stages. The experiment was conducted during the period 2010 – 2012 on the experimental field of Agricultural University, Plovdiv. The parameters of this relationship are established on the base of existing formulas as follows: the two-degree formula of Davidov, the linear formula of FAO, the one-degree formula of Davidov and the linear formula of Stewart. Data for yield and ET (for the different growth stages) are used with the following treatments: 1) no irrigation; 2) irrigation with 30% of the optimal irrigation rate; 3) irrigation with 70% optimal rate; 4) optimum irrigation (supply of 100% of the calculated irrigation norm). For this purpose, the vegetation period of the beans is divided into three sub-periods: (before bud formation, bud formation-flowering and bean formation). For the conditions of the experiment, the dependence is represented best by the two-degree formula of Davidov at R = 0.98. The exponent for the entire growing period is N = 1.8. The values for the different sub-periods are as follows: m1 = 0.05, m2 = 0.05 and m3 = 1.12. This means that the sensitivity of the third sub-period is the greatest, and the first and second have insignificant sensitivity.