SPAD index in the diagnosis of nitrogen status in cauliflower as a function of nitrogen fertilization

Resumo

The correct management of fertilization in cauliflower crop can be obtained by synchronizing the plant demand with the N supply during the crop cycle. There is no study indicating that the SPAD index can be used in the eval­uation of nitrogen nutrition of cauliflower. Thus, the objective of this work was to evaluate the nitrogen nutritional status of cauliflower using the SPAD index, and curd yield as a function of nitrogen fertilization. Four rates of N in topdressing (0, 150, 300, and 450 kg ha^-1) were evaluated in the experimental design of randomized blocks with four replicates. The final harvest of curds occurred from 68 to 76 days after transplanting. The first- and second-year results showed a significant difference. Curd fresh mass showed a quadratic adjustment, with the maximum value of 1,435 and 1,611 g, estimated with the rates of 331 and 307 kg ha^-1 N, in the first and second year, respectively. The critical levels for leaf total N content were between 48.4 and 57.8 g kg^-1; and for SPAD units, between 55.90 and 66.63. The nitrogen nutritional status of cauliflower can be estimated using the SPAD index. The critical level for the SPAD index and leaf N content varied from year to year. Higher production of cauliflower curd fresh mass can be obtained with the application of N rates higher than currently recommended.