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A new empirical equation for the sigmoid pattern of determinate growth, ‘the beta growth function’, is presented. It calculates weight (w) in dependence of time, using the following three parameters: t_m, the time at which the maximum growth rate is obtained; t_e, the time at the end of growth; and w_max, the maximal value for w, which is achieved at t_e. The beta growth function was compared with four classical (logistic, Richards, Gompertz and Weibull) growth equations, and two expolinear equations. All equations described successfully the sigmoid dynamics of seed filling, plant growth and crop biomass production. However, differences were found in estimating w_max. Features of the beta function are: (1) like the Richards equation it is flexible in describing various asymmetrical sigmoid patterns (its symmetrical form is a cubic polynomial); (2) like the logistic and the Gompertz equations its parameters are …