Modelagem do desenvolvimento da batata (solanum tuberosum l.) à campo

Abstract

Potato (Solanum tuberosum L.), Solanaceae, native of Cordilheira dos Andes, South America, is the fourth food crop worldwide, being only overcome by wheat, rice and corn. Potato production in Brazil is concentrated in the states of Minas Gerais, São Paulo, Paraná e Rio Grande do Sul. Thermal time is a simple method and a better time descriptor than the calendar days or days after planting. However, thermal time has been criticized because of the assumption of a linear relationship between plant growth or development and temperature. The objectives of this study were: 1. To determine thermal time from emergency to tuber initiation, from tuber initiation to beginning of senescence and from beginning of senescence to harvest of field grown potato. 2. To construct and evaluate a model to simulate potato development that is superior to current models from a biological as well as from a simulation point of view. Experiments were carried out at Santa Maria RS, Brazil, 9 in the year of 2003 (21/01; 12/02; 28/02; 27/03; 12/08; 15/09; 15/10; 20/11e 24/12) and 6 in the year of 2004 (28/01; 27/02; 26/03; 26/04; 31/05 and 26/08). The experimental design was a complete random block design with four replications. Plots had 3.0 x 3.0 m and consisted of 4 lines of plants with 3.0 m length and 0.75m among them. The distance between plants was 0.33m, totalizing 40 plants/plot. Three plants were chosen from the two central lines. The plants were labeled right after emergence and used to determine the beginning of senescence and harvest time. Tuber initiation was determined by digging up eight plants from the border lines daily (two plants from each plot). Thermal time of different phases varied according to the planting date, calculation method, and the cardinal temperatures. These results indicate that the thermal time should be used with caution to tell time in potato. The proposed development model was superior to the thermal time approach with an average RMSE of 10,41 days. The RMSE value for tuber initiation was 3.7 days.