Test 2 Flashcards
1
Q
corn first cultivated
A
5500+/- central mexico
2
Q
earliest types of corn
A
flint
flour
(modern dent)
3
Q
type of corn pollination
A
open
4
Q
dent corn developed
A
1500 years ago
5
Q
hybrid corn developed
A
1940
6
Q
hybrid seed corn development
A
develop stable inbred lines
cross 2 different inbreds
plant them (F1 hybrids)
offspring yields 2-5X parents
7
Q
selecting hybrid
A
yield transgenic traits maturity cost, availability of seed disease resistance
8
Q
why corn valuable
A
many uses high yielding valuable commodity high in energy long storage life
9
Q
top 3 corn uses
A
- animal feed
- high fructose corn syrup
- ethanol (rising)
10
Q
basic corn botany characteristics
A
zea mays c4 summer annual monoecious 3 root systems open pollinated hybrids
11
Q
3 root systems corn
A
seminal (temporary)
secondary (main)
brace roots (support)
12
Q
5 main kernel types of corn
A
flint (ornamental, popcorn) flour (corn nuts) waxy sweet (white, yellow, mixed) dent (yellow and white, harder)
13
Q
why popcorn pops
A
moist endosperm inside capsule that makes it explode
14
Q
race
A
a class of corn of which all plants of that class share certain characteristics such as ear shape and number of kernel rows 3 main regions with 3 main races each
15
Q
SW region corn
A
- Pima-papago
- SW 12 row flints and flours
- SW semi-dents
16
Q
SE region corn
A
- SE flints
- derived southern dents
- southern dents
17
Q
Midwest region corn
A
- great plains flints and flours
- northern flints and flours
- corn belt dents
18
Q
transgenic types of corn
A
herbicide (RR)
insecticide (Yieldguard Bt)
others coming
19
Q
Main growth stages of corn
A
emergence
V5-7 (apply mid-season fertilizer)
internode elongation (jointing)
reproduction
20
Q
reproduction stages of corn
A
tasseling silking anthesis (pollen shed) milking (soft dough, dough, early dent) late dent black dot (physiological maturity)
21
Q
vegetative growth stages of corn
A
VE - emergence V1 - first leaf V2 - second leaf V3 - third leaf V(n) - nth leaf VT - tasseling
22
Q
reproductive growth stages of corn
A
R1 - silking R2 - blister R3 - milk R4 - dough R5- dent (early and late) R6 - black dot (physiological maturity)
23
Q
corn growth facts
A
leaf number goes to last leaf with a visible leaf collar
first 5 leaves embryonic, rest manufactured after emergence
first leaf round tipped, all others pointed
in field growth stage denoted when 50% showing next stage
24
Q
Growth stage highlights
A
V3: # of leaves and ear shoots programmed
V6-V8: growing point and tassel are aboveground and rapid growing begins
V12-V17: # of kernels/ears and ear size programmed
R3: milk stage occurs about a week after blister denoted by milky fluid in seeds
R6: black dot seen at kernal bases when peeled back with fingernail
25
Corn harvest
entire plant allowed to turn yellow
harvest at 15-18% moisture for optimum quality
grain usually dried before stored
calibrate combine and check field losses periodically
26
6 steps seed to stand
1. seed imbibes water
2. nutrients in endosperm dissolve
3. root radical extends and emerges (2-3 days)
4. shoot extension occurs
5. coleoptile breaks soil surface (5-7 days)
6. embryonic shoots break through coleoptile, turn green
27
ear flex
ability of ear to increase in length, girth, and seeds per ear in low populations
full flex- only produce 1 ear per stalk (adjust to low plant population better)
semi flex- produce 1 big ear 1 small per stalk
28
GDD
```
growing degree days
daily accumulation of heat for crop growth
min- 50 degrees
max- 86 degrees
DD50= (high+low)/2-50
```
29
ideal corn pH
5.8-7.0
| high pH results in Zn deficiency and soil acidity
30
liming corn
```
soil test (Ca determines soil CEC)
quality lime (CCE and fineness factor)
precision grid sampling (saves money)
```
31
N for corn
most important
1-1.5 lbs every bu/acre
half preplant, half sidedress at V5
loamy soils best, clay ties up N
32
realistic yield goals affecting N related to
```
variety
soil
irrigation
markets
resources
fertilizer costs and availability
```
33
potential corn yield reductions from drought stress
vegetative (prior to tassel)- 10-20%
tassel to soft dough- 20-60%
soft dough to maturity- 10-35%
34
most critical irrigation time frame for corn
2 weeks prior to silk - 3 weeks after silk
35
scheduling irrigation
```
soil coring - feel method
soil monitors - tensiometers
pan evaporation monitors - tub gauge
weather stations
university computer program
```
36
irrigation methods
furrow
flood (levee 48hr max standing)
border (precision graded slope)
center pivot (uneven ground)
37
avoid insects corn
```
plant early
rotate crops
good agronomic practices
know your problem insects and select proper Bt GMO technology variety
in-furrow insecticides
weed control
scouting
```
38
Corn insects
```
early season (soil):
cutworm
wireworm
seed corn maggot
sugarcane beetle
mid to late season (foliar):
fall armyworm
corn borers
corn ear worm
aphids
```
39
seed insecticides
```
poncho
cruiser
attendant
senator
intrepid
```
40
at planting spray insecticides
```
lorsban
counter
aztec
force
bifenthrin
```
41
main disease groups in corn
1. seed, seedling (fusarium, pythium, blight)
2. stalk, foliar (anthracnose, rust, gray leaf spot)
3. ear and kernel (smut, aflatoxin, gibberella)
4. viral (dwarf mosaic, maize chlorotic dwarf)
5. nematodes (root knot, 40+)
6. aflatoxin (toxic fungus)
42
aflatoxin management
```
keep grain dry (don't let wet grain sit in hot truck/bin)
harvest unstressed portions seperately
plant early and irrigate
control late season insects
promoted by hot humid weather
harvest at 19-24% moisture
Afla-Guard non toxic strain $20/acre
```
43
main weed groups in corn
annual grasses (crab, signal, barnyard)
johnsongrass
broadleaf weeds (sicklepod, velvetleaf, teaweed)
morningglories
herbicide resistant weeds (goosegrass, palmer amaranth)
nutsedge
44
weed game plan
```
tillage/ preplant burndown
good ag practice
preemergence herbicides
timely use of post emergence herbicides
scout weeds (know them, control early)
crop rotation
timely sidedress N and irrigation
```
45
transgenic hybrid
GMO with resistance to certain herbicides
RR hybrid: resistance to glyphosate
LL hybrid: resistance to liberty herbicide
46
weed control methods
burndown/preplant- clean up before plant
preplant incorporated- applied before plant incorp. into top 2in
preemergence- work horse of corn weed control
postemergence
hooded sprayer- applied between corn rows under hood
flame cultivation- burner heads scorch weeds between rows-
47
Bt corn traits
target above - ground caterpillars, borers and worms
| target below- ground root worms
48
corn breeding objective
```
yield
herbicide, insecticide
drought resistance
clay/poor soil improvement
disease resistance
added value
```
49
grain sorghum history
first cultivated africa then india
US 1700s
5th leading cereal
US #1 producer
50
5 main types sorghum
1. grain sorghum
2. sweet sorghum
3. forage sorghum
4. broomcorn
5. johnsongrass
51
3 main types GRAIN sorghum
milo- US short/compact
kafir- S Africa/India thick/juicy stems (popped like corn)
hegari- N Africa/Middle East like kafir, more drought resist
52
grain sorghum seedhead types
loose (more blackbird problems)
| compact
53
why grain sorghum
```
consistent yields
good rotation crop
steady market
easy to grown and establish
can be integrated with existing equipment
add organic matter to soil
min-notill sorghum most profitable
```
54
3 main growth stages grain sorghum
```
seedling development (emergence)
panicle initiation (seed head extension)
reproduction (flower to maturity)
```
55
3 insect areas grain sorghum
early season
sorghum midge fly (bloom)
late season
56
sugar cane aphid
```
new early season insect
catastrophic numbers
no naturally occurring pathogens
species shift of white sugarcane aphid
up to 100% yield loss
2x week scouting NECESSARY if any seen
sticky messes
```
57
sorghum midge fly
```
adults (small orange fly looks like mosquito)
lay eggs in flowers
maggots hatch and eat the seeds
stagger planting by 2 weeks if possible
careful scouting during flowering
timely insecticide
attracted to johnsongrass
rest easy after soft dough
```
58
grain sorghum advantages to corn
drought evador
more consistent yields
less fertilizer
can grow without irrigation without drastic yield loss
not as sensitive to uneven stands and seedling population
cheaper to grow per acre
great rotational crop for nematode problem
59
grain sorghum disadvantages to corn
```
lower yielding
lower market value
less money per acre
can't grow it with bad rhizome johnsongrass problem
fewer herbicide options
```
