For standardization of definitions, maize researchers developed a guide for identifying different growth stages of maize. Not all plants in a field reach a particular stage at the same time. Therefore, researchers assume that the crop reaches a specific stage when at least 50% of the plants show the corresponding features.
Standardization of definitions allows researchers to relate problems to specific growth stages. Researchers can also compare the phenology of maize under different environmental conditions and experimental treatments.
Researchers divide growth stages into two broad categories:
- vegetative (V)
- reproductive (R)
Additionally, growth stages can be grouped into four major periods (see Table 2 for more details):
- Seedling growth (stages VE and V1)
- Vegetative growth (stages V2, V3... Vn)
- Flowering and fertilization (stages VT, R0, and R1)
- Grain filling and maturity (stages R2 to R6)
Table 2. Growth stages
| Stage | DAS* | Features |
|---|---|---|
| VE | 5 | The coleoptile emerges from the soil surface. |
| V1 | 9 | The collar of the first leaf is visible. |
| V2 | 12 | The collar of the second leaf is visible. |
| Vn | The collar of the leaf number 'n' is visible. The maximum value of 'n' represents the final number of leaves, which is usually 16-23, but by flowering, the lower 4-7 leaves have disappeared. | |
| VT | 55 | The last branch of the tassel is completely visible. |
| R0 | 57 | Anthesis or male flowering. Pollen shed begins. |
| R1 | 59 | Silks are visible. |
| R2 | 71 | Blister stage. Kernels are filled with clear fluid and the embryo can be seen. |
| R3 | 80 | Milk stage. Kernels are filled with a white, milky fluid. |
| R4 | 90 | Dough stage. Kernels are filled with a white paste. The embryo is about half as wide as the kernel. The top part of the kernels are filled with solid starch. |
| R5 | 102 | Dent stage. If the genotype is a dent type, the grains are dented. The 'milk line' is close to teh base when the kernel is viewed from the side in both flint and dent types. |
| R6 | 112 | Physiological maturity. THe black layer is visible at the base of the grain. Grain moisture is usually about 35% |
| * DAS: approximate number of days after sowing in lowland tropics, where maximum and minimum temperatures may be 33° C and 22° C, respectively. In cooler environments, these times are extended. | ||