What happens at each stage of soybean development?

• EMERGENCE: Cotyledons are above the soil surface. Observe the color of the area below the cotyledons. A green color means a soybean cultivar with white flowers. Purple or purplish-green color identifies a soybean cultivar with purple flowers.
• VEGETATIVE: Cotyledons are well developed and the pair of opposite leaves are already open, in such a way that the edges of each single leaf do not touch each other. Thick cotyledons with a dark green color.
• VEGETATIVE V1: The pair of opposite leaves is completely developed and the first trifoliolate isopen, in such a way that the edges of each leaflet do not touch.
• VEGETATIVE V2: The first trifoliolate leaf is extended with the three leaflets expanded and the second trifoliolate already open. The edges of each leaflet are not touching. This indicates the beginning of formation of the first nodules.
• VEGETATIVE V3: The second trifoliolate has its three leaflets expanded and the third trifoliolate is open in such a way that the edges of each leaflet do not touch.
• VEGETATIVE V4: The third trifoliolate is extended with its leaflets expanded with the fourth trifoliolate open. The edges of each leaflet are not touching. Between the V2 and V4 phases of development the yellowing and abscission of the cotyledons is observed indicating that the soybean plant already has a minimum amount of leaves and roots to support its growth.
• VEGETATIVE V5: The fourth trifoliolate has the three leaflets expanded and the fifth trifoliolate is already open. Until the V5-V6 development phases the soy plant expands a trifoliolate every 5-6 days. After these developmental phases, the expansion of a new trifoliolate occurs every 3-4 days. Depending on the cultivar and the time of sowing, the soybean can develop up to 20 trifoliolates (V21) along the main stem.
• REPRODUCTIVE R1: The beginning of flowering is indicated by one open flower on any node on the main stem. Depending on the soya cultivar, the flower may be white or purple.
• REPRODUCTIVE R2: Full flowering. The majority of the in florescence’s in the main stem have open flowers.
• REPRODUCTIVE R3: Beginning of pod development. Pods with 0.5 to 1.5 cm length on the upper third of the main stem. Pods with 1.5 cm indicate the end of flowering.
• REPRODUCTIVE R4: Full pod development. The majority of the pods in the upper third of the main stem with a length of 2 to 4 cm (“pen-knife”).
  • The beginning of the formation of the seed or grain. As of this phase the filling of the pods is noticeable to the touch or visually through the progressive accumulation of dry matter in the seeds. R5.1 means up to 10% of the maximum formation of seeds in the pods located on the upper third of the main stem.
  • The majority of the pods in the upper third of the main stem have between 10 and 25% of their seeds fully developed seeds.
  • Phase corresponding to medium seed formation in the pods. The majority of the pods located in the upper third of the main stem are 25 to 50% fully developed.
  • The majority of the pods located on the upper third of the main stem with 50 to 75% fully developed seeds.
  • The majority of the pods in the upper third of the main stem have between 75% and 100% of their seeds fully developed.

Nutrient Deficiency

MICRONUTRIENTS

• Zinc:Smaller new leaves having a spear shape and bearing chlorotic areas which may turn into a grey or brown coloration. Plants are smaller due to internode shortening. Bending of the stem and low production of the racemes.
• Boron: Slow development of the growing points which may die. The leaflets of newer leaves remain smaller, deformed, wrinkled, having a green-blueish coloration. Low flower production and marked abortion.
• Manganese: The new leaves become gradually yellowish between the veins. The plants develop poorly, having small leaves. Brown necrotic areas appear on leaves as the deficiency increases.
• Iron: New leaves go from a pale green to a whitish coloration between the veins. Then, the veins also lose their coloration and necrotic spots may appear having a brown coloration close to the border.
• Copper: Necrosis at the tip of the leaflets of new leaves which progresses towards the border that curls up. The leaves take on a “dry” appearance and the color changes to a bluish green, bronze green or olive green.
• Molybdenum / Cobalt: Chlorotic leaves having symptoms similar to those due to lack of nitrogen. Flowers and raceme fall off. Reduction in vegetation and root growth, in the weight of the beans and production of them. Small and little active nodules having an internal pale yellow or greenish coloration.

MACRONUTRIENTS

• Nitrogen: Lower leaves bear an overall chlorosis and may fall off as the symptom progresses. Newer leaves take on a lighter coloration, poor vegetation and root development.
• Potassium: Older leaves are yellowishly speckled at the borders of the leaflets. This chlorosis progresses toward the center of the leaflets while a necrosis begins at the borders and progresses toward the center. Pods are poorly formed and numbers are reduced.
• Calcium: Reduction of the meristem growth. The terminal buds become deteriorated and a petiole collapse occurs. The newer leaves become wrinkled with chlorosis beginning at the border and progressing toward the center. Marked flower and pod and seed abortion.
• Phosphorus: Older leaves are smaller bearing a bluish dark green coloration. There may appear a chlorosis from the tip down to the base of the leaves. Purple color appears at the base of the stem. Pod production is reduced.
• Magnesium: Initial yellowing of the borders and progressing to the center of older leaves which become chlorotic between veins. There may be a drying of the border.
• Sulfur: The new leaves bear first the symptom of an overall chlorosis and a poor size. Then the leaves become yellowish as if it were due to a nitrogen deficiency.