Exam 1 Flashcards
2019
What is the formula for GDU’s?
[(max temp + min. temp)/2)]-Crop threshold temp.
What is limits on GDU calculation?
Temps must be between 50F and 86F.
What is threshold temp for corn?
Corn-50F
How do you figure the accumulated GDU’s to-date?
Do the formula for each day and add the answers together.
What are GDU’s used for?
- when pollination should occur
- when black layer should be reached
Why is seedling establishment critical to corn plants?
Because the seed coat is broken and several organisms immediately begin attacking the new sprout.
What is the most common corn planting depth?
2”
What does Fergie plant corn at here at MSU Farm? Why?
2-1/2” to 3” because of blackbirds
Vegetative Stage of Growth for corn is classified by:
The number of collars on leaves that are visible.
What occurs at V6 in corn?
- The growing point (meristem) is now at the soil surface
- Tassel development begins
What happens at V8 in corn?
- ear initiation begins
- # of rows of ovules which potentially will be kernels starts to be determined
- between V8 and V12, number of ovules per ear is determined
What happens at V12 in corn?
-# of ovules per ear has been set
What is an ear of corn? Where do ear shoots form? How many develop into a full ear?
- An infloresence structure that terminates on lateral branches on the corn.
- An ear shoot will form on every above-ground node 6-8 nodules below the tassel.
- Only the upper 1 or 2 will fully develop into an ear
What is VT in corn? What has occured at this point?
- The tasseling stage
- The tassel has emerged but the silk has not.
What is R1 in corn?
When does it occur in corn?
- Beginning of the reproductive stage
- Silking occurs (becomes visible outside of ear)
- Occurs 1-3 days after VT
What is the silk on corn?
The stigma and style (part of the pistol) of the female flower on the ear.
What is R2 in corn?
Blister stage
What is R3 in corn?
Milk Stage
What is R4 in corn?
Dough stage
What is R5 in corn?
Dent stage
What is R6 in corn?
Physiological maturity is reached (formation of black layer)
What happens during pollination in corn?
Tranfer of pollen from the tassels to the silk.
How is corn pollen transferred?
Easily via the wind.
Describle fertilization in corn.
- pollen lands on the silk and germinates
- produces pollen tubes that grow down to the ovule (kernels)
- sperm cells go down the tubes and fertilize the ovules which potentially become kernels
What is Xenia?
The immediate observable effect of foreign pollen on the endosperm, which is accounted for by the double fertilization mechanism.
Ex> When white corn is pollinated by yellow corn and therefore has yellow kernels or vice versa.
How is problems arising from xenia adressed?
Planting dates or maturity differences in varieties.
Difference in early season varieties of corn vs. late season varietes?
Due to the number of GDU’s required for the vegetative period of growth. Is similar to the number of GDU’s required from silking to maturity.
What does black layer mean in corn?
- indicates physiological maturity.
- marks end of nutrient transfer to kernels
When does black layer in corn occur (in general, not by variety)?
When moisture drops below 35%
Is a dry down still required after black layer is reached?
Yes
What is significant of the pollination and fertilization period in corn?
- act as the on/off switch for eventual yield
- fertilization must occur for a kernel to develop
What does drought stress do to corn that is in the pollination and fertilization period?
- delays silk emergence in relation to pollen shed
- silks may become unreceptive (doesn’t really happen, just appear to be)
Do pollen tubes continue to grow down silks during drought stress?
Yes
What are two examples of herbicide tolerant corn?
- Roundup Ready
- Liberty Link
What are 2 examples of a new type of herbicide resistant variety of corn?
- RoundupReady2
- Viptera
What is the purpose of the Viptera variety of corn?
It has an additional gene for the control of lepidopterea insects.
What are two examples of older types of corn varieties?
-Bt corn
>Corn rootworm resistant varietes
>European corn borer
What are 5 different types of corn by kernel traits?
- Dent (yellow corn)
- White corn
- Waxy corn
- High Lysine corn
- Quality Protein Maize (QPM)
What was the purpose of waxy corn? When was it developed?
Is high in amylopectin. It was developed for starch during WWII.
What is the purpose of High Lysine Corn?
It contains a gene that increases lysine content of endosperm proteins.
What were the two issues with high lysine corn?
- ear rot
- soft kernels
What were the traits of Quality Protein Maize?
-new higher lysine corn with improved yield and kernel traits.
What is liguleless?
A gene in corn that gives an upright leaf orientation.
What are some new varieties of corn by trait?(2)
- Drought resistance
- Alpha
What is alpha-amylase corn? What is its traits? Trade name? Can humans consume it? Where can you sell it?
- A corn variety that has a thermostable enzyme (alpha-amylase) in the grain that can help in ethanol production. The enzyme helps break down starch.
- Enogen
- Not consumable by humans
- Can only market at ethanol production markets or livestock feed markets
What is the VE stage in soybeans? When does it occur? What does it depend on?
- emergence stage
- 5-21 days after planting
- Temp. and moisture content
What happens at VC in soybeans?
- unifoliate leaves have unrolled
- leaves are opposite
- first node
What happens at V1 in soybeans?
- 1 unrolled trifoliate leaf
- 2 nodes
What happens at V2 in soybeans?
- 2 unrolled trifoliates
- 3 nodes
- nodules have been established
What happens at V6 in soybeans?
-roots reach across 30” rows
What are the Reproductive stages of soybeans?
R1- beginning bloom R2-full bloom R3-beginning pod R4-full pod R5-beginning seed R6-full seed R7-beginning maturity R8-full maturity
At what rate do soybeans advance from VC to V5? V5 to R5?
VC-V5-every 5-7 days
V5-R5-every 3-5 days
What is the formula for Nitrogen fixation?
N^2+6e-+6h^+»»»»2NH^3
What does early-season nitrate presence do to soybeans?
-reduce nodule formation
How long does it take before N-fixation supplies soybeans with most of their N needs?
2-3 weeks from planting
How does corn like its climate?
Warm days and cool nights
What are 3 determining factors of water availability in crops?
- Rain during season
- Irrigation (is it available or not)
- Moisture stored in soil
3ft deep soil holds ____in. of stored water.
6”
10ft deep soil holds ____in. of stored water.
20”
What 2 factors determine the amount of water needed in a certain area?
- Humidity
2. Temp.
How much rain does corn in our area need during one growing season?
20-25”
What crop is good for areas with low amounts of rain fall? Why?
Sorghum. Because it has a specialized stomata that improves the plants water use efficiency.
What primarily causes kernel loss in corn?
heat
What is the cold tolerance of soybeans?
High.
What are soybeans very sensitive to during growth?
photoperiod (day length)
Soybeans are ____-day plants. This means they:
- short-day plants
- means that shorter days encourage earlier flowering and longer days delay flowering.
What does exessive light cause soybeans to do?
Stay green and not flower
____ is more important than light in regulating flowering in soybeans.
Temperature
Temps over ___C/____F speed up soybeans flowering.
25C/77F
What is the range of soybean maturity groups? What groups can we grow here?
What are the specific two types we use most here?
- 00-IX
- III and IV
- 4.8 and 4.9
What is the purpose of having different soybean maturity groups?
Responses to photoperiod vary between the groups; lower #’s are grown in the north and higher numbers are grown in the south to account for different season lengths and different temps.
If you plant the same cultivar of soybeans in KY and MS and temps are the same at each location, which will flower first?
MS due to shorter days (further south)
What are the two types of soybeans when it comes to vegetative growth? What is the difference in the two? What decides this?
Determinate- stops vegetative growth completely when flowering begins. (will not get taller)
Indeterminate- continues vegetative growth after flowering begins for short period of time. (may continue to get taller)
-Determined by 1 gene.
Where are determinate soybeans usually grown?
In the southern US
Where are indeterminate soybeans usually grown?
Northern US
What type of determinance is most common in soybeans grown here?
Either. Neither yields better here.
What are two key differences between determinate and indeterminate soybeans?
- determinate soybeans flower quickly all over and in a short time span and have many mods on their raceme (long flowering stalk)
- indeterminate soybeans flower from the bottom up over a long period of time and have only a few flowers on their raceme.
What are semi-determinate soybeans? Why were they developed?
- Type developed for northern areas that are very fertile.
- Because indeterminates lodge and determinates suffer yield loss
What do soybeans rely on for pollination?
Themselves; they are self-pollinated.
Are soybeans more or less tolerant than corn of short periods of stress? Why?
- more tolerant
- because they produce more flowers than pods that the plant can support.
What period is the most critical for soybeans?
R4-R6 (seed filling period)
What are soybeans particularly intolerable to?
Drought (especially late season)
When does physiological maturity occur in soybeans? What does this mean? What indicates this?
- 55-60% moisture
- dry matter accumulation within seeds has ended
- when soybean seed has lost all of green color and is yellow (only requires 1)
What stage does soybeans reach physiological maturity?
R7
What moisture content do you harvest soybeans at? What is better, slightly wet or too dry?
- 18-13%
- slightly wet, too dry reduces weight
What is the minimum temp (threshold temp) for soybeans?
49-50F (slightly lower than corn)
Emergence issues are more common in soybeans or corn?
soybeans
What is the ideal daytime temp for soybeans?
85F
Ideal climate for soybeans is:
Why?
- cool days and warm nights
- because soybeans accumulate starch during the day and distribute it during the night throughout the plant
What happens when soybeans experience water stress early in the season (such as during flowering)? What happens when water stress occurs late season (during seed filling)?
- they may reflower later if rain comes
- pods are aborted
Majority of soybean varieties used today are of what variety?
RoundupReady.
What is a new trait introduced in soybeans? What is their purpose?
- High Oleic Soybeans
- They are used for preservatives to avoid hydrogenation which is responsible for transfats.
Are soybeans hybrids?
No.
What is the formula for stand counts?
of plants in a row sample/row width (ft.) x row sample length (ft.) = x/43560
