Maize

This section describes the maize growth cycle and its stages through a practical and dynamic approach. In addition, you will also find a guide detailing the main nutrient deficiencies that can affect your crop and how to identify each of them.

What happens at each stage of maize development?

  • EMERGENCE (VE): Begins with the elongation of the primary root followed by the seminar roots which origin from the cotyledonal node. Next, furrowing into the soil surface, the coleoptile emerges to support the plumules. It is made up by five rudimental leaves that emerge from the interior of the coleoptile, starting the growth of the aboveground plant. The seed remains under the soil surface.
  • VEGETATION (V1): Following the emergence (VE), the subsequent vegetative stages are identified by the successive expansion of the leaves. Each expanded leaf presents visible auricular (collar area). This is the identification criteria of each vegetative stage. The lower
    and round shaped leaf is not considered for the counting. Thus, the V1 stage is identified by the expansion of the first apical leaf and visible auricular (collar). The seminal roots begin growth and branching. At this time the stem apex of the plant is below the soil surface.
  • VEGETATION (V2): Second expanded leaf with visible collar. The plant is ready to start the photosynthetic activity. The branched seminal
    roots and the nodal roots are in greatly growth. The stem apex still remains under the soil surface.
  • VEGETATION (V3): Third expanded leaf with visible auricular. Photosynthetic activity in progress. The nutritional reserves are running out. Seminal roots activities ceased. Nodal roots are growing and branching. The stem apex remains under the soil surface.
  • VEGETATION (V4): Fourth leaf expanded with visible collar. Root system in development with differentiated branches and absorbent hair. The stem apex (growing point) is still below the soil surface. The differentiation between male (panicle) and female (ears) flowers starts between the stages V4 and V6, defining the potential yield of the plant.
  • VEGETATION (V5, V6, V7, VN): The identification of the phenological vegetative stage of the maize is based in the observation of the successive leave expansions along with the visualization of the auriculars. Following the expansion of the fourth leaf (V4) occurs the expansion of the fifth (V5), sixth (V6), seventh (V7) and so on until the “n-leaf” (Vn) corresponding the last one formed before the differentiation of the male inflorescence (tassel). According to the genotype, 18 or more leaves of maize might be observed. From this point on only phenologic vegetative stage most important for the management of the culture will be illustrated. V5 to V6 stages the growth area
    reaches the surface of the soil.
  • VEGETATION (V8): Plant with the eighth leaf expanded and visible collar. Root system well distributed in the soil and the adventitious roots begin to grow. The intense elongation of the stalk in height and diameter is observed. Accentuates the development of the male inflorescence (tassel) and the development of the ears increases between the sixth and ninth nodes above the soil. Between the stages V7 and V9 the number of grain rows in the ear is confirmed.
  • VEGETATION (V12): Plant with the twelfth leaf expanded and auricular visible. The adventitious roots are well developed and visible. The plants present 85 to 90% of the leaf area and a high growth rate of the stalk, tassel and upper ear. The tassel reaches maximum development concurrently with the beginning of the silk growth (tassel). Between the stages V12 and V14 the size and number of ear in the plant are confirmed.
  • VEGETATION (R1): Male flowering. Ranges from the partial rise to the visualization of the last branch of the tassel. This stage occurs the greatly growth of the ear silks. The male inflorescence is observed to occur 2 to 4 days prior to the manifestation of the silk (tassel). In the USA it corresponds to “VT” stage, that means, “visible tassel”.
  • BLOOMING (R2): Female flowering and pollination. Starts from the appearance of the first visible ear silk on. The stalk elongation ceases. The ears show their viscid silks, which grow up until pollinated. The silk appears for 3 to 10 days. Pollen grains dispersion occurs 2 to 3 days prior the emission of the silk and lasts 5 to 8 days. In contact with the silk, the pollen grain germinates giving rise to a pollinic tube, responsible for the fecundation of the egg inserted into the ear. Fertilization, on average, occurs 24 hours following pollination.
  • BLOOMING (R3): Milky kernels. Soluble substances start to accumulate in the grains, increasing their volume and weight. In the seeds, the differentiation of the coleoptile, radicle, and rudimentary leaves begin. The kernels are between white and light yellow on the outside and resemble a blister in shape. By the fingernail-pressing, the grain tegument breaks up releasing a large amount of soluble solids (milk). In the field, the ear silk is verified to drying, darken and cannot be pulled by hand.
  • BLOOMING (R4): Doughy kernels. The starch accumulation is very prominent, and the kernels gain considerable weight. When fingernail-pressed, the kernels are relatively consistent, with little milk. In the seeds, the embryonary structures are already totally
    differentiated. In the field, the silk, now darker, is verified to be easily pulled by hand. This stage is known by means of the sweet maize point.
  • BLOOMING (R5): Farinaceous kernels. The concavity on the upper grain part (dented genotypes) appears. With a larger volume due to the
    continuous starch accumulation, the kernels are in a transition stage, from the dough to the farinaceous, and become harder and harder. The humidity inside the kernels is about 70%. In the seed, the embryonic leaves are ready. The light shelled cob starts getting darker. It is the optimum point for silage.
  • BLOOMING (R6): Hard-farinaceous kernels. In the upper part of the kernels of the dented genotypes, the presence of the concavity (dents) is prominent. The starch line is above the half of the kernel indicating the greatly accumulation of starch. Simultaneously, the kernels
    and the plant lose humidity. The humidity is about 55% in the harder and harder kernels. The seed is morphologically developed.
  • BLOOMING (R7): Physiological maturity of kernels. Total cease of starch accumulation in the grains and leaf yellowing. It is the maximum dry matter accumulation in the kernels and maximum seed vigor, with 30 to 38% humidity. This stage is identified by a black layer at the point of insertion of the grain into the cob. Harvesting must be effectuated with 22 to 24% humidity.

Nutrient Deficiency

MICRONUTRIENTS

  • Zinc: White or yellowish stripes between the main vein and the borders to which necrosis may follow and purple tints may occur. In extreme cases, a shortening of the internodes may take place.
  • Boron: Elongated white stripes on new leaves. Poor pollination, flower abortion, smaller ears and poor seed formation. Maize seeds bear voids at the silk end. A shortening of the internodes and a smaller stalk diameter.
  • Manganese: Intervein chlorosis on newer leaves. In more severe cases, long white stripes show up in the tissue and the tissue in the middle of the chlorotic area may die and fall off.
  • Iron: Intervein chlorosis starting with the newer leaves at the whole extension of the blade. A reduction in the ear formation. Under severe conditions, the new leaf will turn white.
  • Copper: The newer leaves become yellowish as soon as they begin to unfold, then the tips bow and bear necrosis. The margins are necrosed. The leaves twist or spiral.
  • Molybdenum: Small white spots on the larger interveins, leaf bending along the central vein. The manifestation of the visual deficiency symptom of molybdenum is infrequent. However, low nutrient levels at the leaves affect the utilization of nitrogen by the crop.

MACRONUTRIENTS

  • Nitrogen: Yellowing of the older leaves from tip to the base in a “V” shape. Drying beginning at the tip of the leaves and progressing along the central vein. Thin stalks. Small ears.
  • Potassium: Cholorosis at the tips and margins of older leaves followed by drying of the tissue. The plant becomes susceptible to stalk rot. Reduction in the stalk diameter and in the overall production.
  • Calcium: The upper leaves successively bear a thin yellowing of the borders, a drying off effect, a necrosis and wavey edges of leaf margins. New leaves are slow to unfold.
  • Phosphorus: A dark green color of the older leaves followed by purple tints at the tip and margins; the stalks may also become purple. The ear formation is greatly affected.
  • Magnesium: The older leaves yellow at the margins and between veins, yielding a striped aspect. A necrosis of the chlorotic areas may follow. The underside of leaf turning purple.
  • Sulfur: reduction in the leaf volume and size. Chlorotic leaves having whitish spots at the base and a purple gradient beginning at the middle of the plant and creeping towards the sheath. Important: for every 10 parts of N, maize needs one part of S.