Soybeans

Question 0

Planting a lower maturity group south of its adaption zone will result in what?

Answer 0

The plant to flower earlier in the season.

Question 1

Soybeans flower based upon what factor

Answer 1

Photoperiod or Day Length

Question 2

Planting a higher maturity group north of its adaption zone will result in what?

Answer 2

The plant will flower earlier in the season.

Question 3

Define growth stage VE

Answer 3

• Cotyledons have emerged

Question 4

Define growth stage VC

Answer 4

• Unifoliate leaves have unrolled

- First node

Question 5

Define growth stage V1

Answer 5

• One unrolled trifoliate leaf

- Two nodes

Question 6

Define growth stage V2 and subsequent vegetative stages

Answer 6

• Two unrolled trifoliate leaves (opposite)
• Nodules have been established
• Three nodes (plant growth stage +1)

Question 7

Nodulation occurs on the roots of soybeans; what is nodulation?

Answer 7

Nodulation is the effect of a mutalistic relationship between legumes and rhizobium bacteria (Bradyrhizobium japonicum).

This relationship provides the bacteria sugars and then plant usable nitrogen.

This process is inhibited by the presence of NO3

Question 8

How fast do soybean plants progress between growth stages?

Answer 8

VC-V5: Every 5-7 days

V5-R5: Every 3-5 days

Question 9

Define growth stage R1

Answer 9

Beginning Flowering

• On open flower at any node
• Rapid root growth

Question 10

Define growth stage R2

Answer 10

Full Flowering

- An open flower at one of the uppermost nodes

Question 11

Define growth stage R3

Answer 11

Beginning Pod

• Pod 3/16in long at one of the four uppermost nodes
• 60-75% of flowers abort and never contribute to yield

Question 12

Define growth stage R4

Answer 12

Full Pod

• Pod is 3/4in long at one of the four uppermost nodes
• Pod number is determined at this stage
• Start of critical yield determination period

Question 13

Define growth stage R5

Answer 13

Beginning Pod

• Seed 1/8” long in pod at one of the four uppermost nodes
• Large demand for water and nutrients
• DM accumulation will stop between R5 and R6

Question 14

Define growth stage R6

Answer 14

Full Seed

- Pod contains a green seed that fills the pod cavity at one of the four uppermost nodes

Question 15

Define growth stage R7

Answer 15

Beginning Maturity

- Any one pod achieves its mature color.

Question 16

Define growth stage R8

Answer 16

Full Maturity

• 95% of pods have achieved mature color
• Harvestable 7-10 days after R8

Question 17

What is the optimum pH level for Soybean production

Answer 17

pH 6.8-7.0

The optimum pH for Bradyrhizobium japonicum