HIGHLIGHTS
Improvement of the simulation by calculating a temperature function with the daily minimum and maximum temperatures.
Equation to determine the maximum rate of node appearance of soybean cultivars recommended for Southern Brazil.
Maximum node appearance rate varies with the maturity group and not with the type of growth of soybean cultivars.
Key words:
Glycine max; agricultural models; stages of development; phenology; plastochron
ABSTRACT
Agricultural models that simulate the appearance of nodes are tools that describe the vegetative stages of soy and help to understand the physiological processes of the plant. This study aimed to calibrate and validate a non-linear node appearance model for soybean cultivars recommended for Southern Brazil. Data from 47 experiments carried out in the Rio Grande do Sul between 2010 and 2018 were used, with 35 soybean cultivars of determined and indeterminate growth type and relative maturity groups ranging from 3.9 to 8.3. The calibration of the node appearance model was performed using the least-squares method of the residue, between the number of observed and simulated nodes, for three versions of the model regarding the temperature function calculation [f(T)]. The performance of the model was validated with data on the number of nodes in experiments and crops, with irrigated and non-irrigated water regimes, highland and lowland environments. The simulation of the number of nodes is improved when a temperature function is calculated with the minimum daily air temperature and another with the maximum daily air temperature. Then the average of the two functions is calculated (Tmm version). Also, the general equation, which does not consider the growth type of the cultivar, can calculate the maximum rate of nodes appearance (NARMAX) without loss of precision in the simulation.
Key words:
Glycine max; agricultural models; stages of development; phenology; plastochron
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The blue color is the Tmean version (A, D), the green color is the Tmm version (B, E), and the orange color is the Thmean version (C, F). The circles are the numbers of nodes simulated with NARMAX obtained through the general equation (A, B, C), and the triangles are the numbers of nodes simulated by the equation according to the type of growth (D, E, F). The solid line is the 1:1 line. The inserts are the residues between the simulated and observed (Si - Oi)
The blue color is the Tmean version (A, D), the green color is the Tmm version (B, E), and the orange color is the Thmean version (C, F). The circles are the numbers of nodes simulated with NARMAX obtained through the general equation (A, B, C), and the triangles are the numbers of nodes simulated by the equation according to the type of growth (D, E, F). The solid line is the 1:1 line. The inserts are the residues between the simulated and observed (Si - Oi)
The blue color is the Tmean version (A, D), the green color is the Tmm version (B, E), and the orange color is the Thmean version (C, F). The circles are the numbers of nodes simulated with NARMAX obtained through the general equation (A, B, C), and the triangles are the numbers of nodes simulated by the equation according to the type of growth (D, E, F). The solid line is the 1:1 line. The inserts are the residues between the simulated and observed (Si - Oi)
The solid line is the 1:1 line. The inserts are the residues between the simulated and observed (Si - Oi)
Cultivars with RMG ≤ 5.5 (A), 5.5 < RMG < 7 (B), RMG ≥ 7 (C). Soybean sowing in August/September (D), October/November/December (E), and January/February/March (F). The solid line is the 1:1 line. The inserts are the residues between the simulated and observed (Si - Oi)