Abstract

Plant diagnosis was proven to be useful for predicting maize growth condition. The number of days to male flowering and that to silk emergence differed among the four sites, reflecting differences in growth condition. Maize stalk weight decreased when the number of days to male flowering exceeded 65. Two growth indexes (GIs), plant height and stem diameter, well predicted maize fresh weight as expressed by the equation: Fresh weight = -0.013 + 1.26 × (Plant height × Stem diameter) (r² = 0.57). Those two parameters changed with the growth stage according to the maize growth condition. GI monitoring revealed that week 4 (W4) or week 8 (W8) after germination was the determinant of overall maize growth. Leaf color also changed in the course of growth; leaf color at W4 was the best indicator of maize grain yield. Such plant diagnosis parameters as GI and leaf color are useful for the determination of optimum fertilizer application time.

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