SPAD Index in Oregano Crop: A Proposal for Interpretation Ranges

The analysis of non-destructive variables in plants, such as the SPAD index, shows a growing trend of adoption in the field. However, it is necessary to determine comparative reference standards, aiming to assist in the interpretation of results obtained in the field and in making decisions about the management to be adopted. The study aimed to propose levels of interpretation of the SPAD index in oregano leaves based on the yield of the crop. The experiment was conducted in protected environment, randomized blocks design was adopted with four replications in 6 x 4 factorial scheme- six levels of water replacement (60, 70, 80, 90, 100, and 110% of the crop evapotranspiration-ETc) and four doses of bokashi (0, 100, 200, and 300 g m-2). For analysis, the data were subjected to variance analysis, multivariate analysis, regression and correlation. Productive management (water replacement and bokashi dose) influences the SPAD index response. Through mathematical analysis of the relationship between SPAD index and relative yield, the sufficiency ranges based on the SPAD index were determined in very low (<37) low (37-44), medium (44-46) and high (>46). The proposed classification of the sufficiency range for the SPAD index allows advances in the productive management of the oregano crop.