A randomized block experimental design was used, with a 3 x 4 x 6 factorial arrangement, consisting of four nitrogen rates (0, 60, 120 and 180 kg [ha.sup.-1]), three fertilizer application forms (at sowing, as top-dressing, and 50% at sowing and 50% as top-dressing), and six growth stages (21, 29, 43, 57, 71, and 87 DAE), with four replications.
N fertilization was performed according to the treatments (100% at sowing, 100% as top-dressing, and 50% at sowing + 50% as top-dressing).
Plant height fitted to linear models when the nitrogen was applied 50% at sowing and 50% as top-dressing (50S50T), and to quadratic models when applying 100% of the nitrogen at sowing (100S) or 100% of the nitrogen as top-dressing (100T); grain yield data fitted to a quadratic model.
Applications of 100S may reduce application costs and nitrogen application as top-dressing. Significant interaction between N application times and rates was found in 2016 (Table 3).
Nitrogen fertilization at doses higher than 1,600 mg N [dm.sup.-3] as top-dressing led to a reduction in vigor.
Number of leaves (NL) (A) and shoot length (SL) (B) in the initial development of 'pitombeira' as a function of days after transplanting (DAT) and nitrogen doses as top-dressing
Root length (RL) in the initial development of 'pitombeira' under nitrogen doses as top-dressing
Shoot dry matter (SDM) (A) and total dry matter (TDM) (B) in the initial development of 'pitombeira' under nitrogen doses as top-dressing
In general, the mean values indicate a higher response of the evaluated variables to the application of 1/3 at sowing + 2/3 as top-dressing, which suggests that canola plants need a lower amount of N initially and that this demand increases along the crop cycle.
Similar performance of the variables was observed for the split application of N, as 1/3 at sowing + 2/3 as top-dressing, in comparison to 2/3 at sowing + 1/3 as top-dressing (Table 3).
The superior performance of canola with the split application of N is evident when compared with its single application, whether at sowing or as top-dressing (Table 3).
However, a higher oil production in the mass of grains was observed for the split application of N, compared with single applications at sowing or as top-dressing. Cheema et al.