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