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. 2019 May 27;5(5):e01695. doi: 10.1016/j.heliyon.2019.e01695

Table 3.

Coded and natural values of selected factors at different levels.

Factors Levels
-1.68 -1 0 +1 +1.68
NaNO3 1 2 3 4 5
K2HPO4 0.2 0.6 1 1.4 1.8
pH 3.2 5.2 7.2 9.2 11.2