unit 7: major agronomic crops chapter 17. unit 7: major agronomic crops unit 7 objectives: genetic...

Unit 7: Major Agronomic Crops

Chapter 17

Unit 7: Major Agronomic Crops Unit 7 Objectives:

Genetic and environmental factors affecting production of corn, soybeans, etc.

Growth requirements Understand the importance of crop rotation

and its implications Identify pests and the need for their control

Unit 7: Major Agronomic Crops Corn

A.k.a Maize Several varieties of corn

Dent, sweet, popcorn, etc. Key factors of a successful system

Recognize and understand the types of interactions that occur among production factors, and what limits yield

Develop management systems that maximize the benefits of those interactions

Knowledge of growth and development factors is essential


Temperature Can survive brief adverse temps

Low ~32, high ~112 Growth decreases when temps are <41 or >95 Optimal range 68 – 73

Planting Date Recommended planting date – mid-April to mid-May 100-150 GDD’s needed for emergence Seed treatments and seed vigor may survive up to 3

wks if soil conditions are not excessively wet 50º temp at ½ to 2” depth indicates enough warmth

for planting Germination is very slow at lower temps


Latest planting date without much reduced yield June 15th to July 1st

Plant only in dry conditions “Mudding in” will decrease yield greater than waiting

for dryer conditions No-till can be planted at the same time as

conventional Plant long-day varieties first

Spread workload Reduce widespread disease risk Increase chance of pollination of some varieties Increase harvest window


Planting delays or replanting may necessitate a change in variety selection

Seeding Depth Varies w/ soil and weather conditions Normal conditions

½ to 2” depth provides frost protection, allows for adequate root development

Shallower planting – poor root development Early planting – no deeper than 1 ½” depth

because of increased moisture As evaporation rates increase and soil warms can plant

deeper


Row Width Most perform well in 30” rows 15-20” rows can increase yields by 3-5%

Both in moderate and high planting populations Both high and moderate yields

Must match equipment to row spacing Plant Populations and Seeding Rate

Grain production 20-30,000+ plants/ac depending on hybrid and

environment Corn silage production

May increase another 2-4,000 plants/ac Newer varieties may require >24,000 to reach yield

potential


Seed companies usually recommend seeding rates Higher seeding rates only recommended for sites w/

high yield potential, high soil fertility, high water-holding capacity

Uneven spacing & emergence may reduce yield potential

Uniform spacing is critical Crowding will result in too much competition and

barren ears, lodging Taller plants cause difficulties for smaller plants Reasons for delayed emergence

Soil moisture variability Poor seed-to-soil contact Malfunctioning planter Soil temp variability


Soil crusting prior to emergence Herbicide injury Insect or soilborne disease pressure

Replanting 10-15% usually fail to establish healthy stands

Number increases as season progresses w/ insects, weather, etc.

Corn is very able to grow out of damage Growth point is below ground until ~6 leaf stage If leaf growth resumes, plant will produce as normal

Making the decision Planting date and stand Earliest possible replant date and stand Cost of seed & pest control


Pests Insects

Earworm, corn borer, aphids, cutworm, etc. Controlled by insecticides from tassel emergence

through grain drying Diseases

Southern leaf blight, northern leaf blot, diplodia rot Select disease resistant varieties Improve management May use fungicides


Fertilizer Requirements Vary according to soil tests Corn removes:

N, P, K, micros Must be supplied in a fertilization program

Crop Rotations Corn-SB most common rotation in the Midwest Many advantages over growing each continuously

More weed control options Fewer difficult weed problems Less disease and insect buildup Less N fertilizer use

Corn following SB typically yields 10% more than continuous corn


No-till corn is better following SB than other crops More pronounced advantage in droughty years

Soybeans Planting Date

Has more effect on yield than any other production practice

Delayed planting can decrease yields from ¼ to 1 bu/ac/d

Depends on row width, date, plant type Canopy should develop by flowering or end June

(whichever comes first) Regardless of planting date, row width, plant type Row width <15” if planting in early May to canopy by

June 30


Early canopy increases grain yield More sunlight converted to grain production

Vigorous stands difficult to establish if planting too early

Seed treatments, good seed-soil contact, reduced seeding depth may help

Herbicide must control weeds longer

Row Spacing Average row width <12

For any planting date, variety, or seeding rate: Yields increase as row width decreases b/c of early

canopy formation 1/3 bu/ac increase/inch of row reduction below 30”


Grain drills are as effective as bean planters Must remove wheel tracks if tillage is used

Seeding Rate Not very responsive to changes in seeding rates >250,000/ac

Tall plants Weak stalks Lodging

<60,000/ac Short Many branches Pods too close to soil surface High harvest losses


Seeding rates producing a harvest population of 80-140,00/ac adequate if planting is before May 15

Delayed planting shoot for 100-160,000/ac Uniform spacing is critical

Yield losses can be 5% if spacing is not proper and uniform

Rapid growth early in the season critical for high yields

Height doesn’t increase after flowering Planting Depth

1-1 ½” ideal when tillage is used ¾ to 1” for no-till

Better for later planting times also No large clods in the soil


Deeper planting increases the risk of soil crusting and reduced emergence

Combined pressure of many plants needed to emerge

If hypocotyl breaks, seedling will not emerge Variety Selection

Most varieties have genetic yield potentials well over 100 bu/ac

Environment & production system sets the yield Select a variety that matches the system rather than

just selecting for yield Smaller seeds if using a grain drill will improve

metering and stand uniformity Each 10d delay planting in May decrease maturity by

3-5d in the fall


Disease Control Phytophthora root rot is a major problem anywhere

SB are planted Most susceptible in the seedling stage Saturated soils w/ temps >60 increase risk Don’t grow susceptible varieties in wet or poorly

drained soils Use seed treatments for control, or resistant varieties

w/ seed treatment Pythium & Rhizoctonia

Damage greatest on poorly drained soils and high rainfall seasons

Controlled by fungicide seed treatments


Sclerotinia stem rot Severe if wet weather during flowering No known resistance, some varieties more suscpetible Water soaked lesions, cottony growth, black irregular

shaped sclerotia Brown stem rot

Can severely reduce yield Enters through roots and grows through xylem w/ plant

Interferes w/ water flow Symptoms develop after flowering

Internal browning of the stem in August Foliar symptoms are rare Leaves may wilt and stay attached to the plant


Phomosis seed rot Occurs when rainfall is intermittent during dry-down

and harvest Incidence increases as grain remains in the field after

ripening Use varieties that will increase the timeliness of harvest Can be decreased w/ crop rotation

Soybean Cyst Nematode Found in the south in early 1950’s

Has migrated to the Canadian border Symptoms

Can be easily confused w/ other problems Usually circular patterns of stunted yellow plants Evident in July or August when drought stressed


May see symptoms under normal conditions if SCN population is high

May increase in size in the direction of tillage each yr.

Laboratory analysis required for identification Roots may be stunted and have few rhizobium

nodules Detection of SCN

Sample suspect soils May see females on roots, but must identify larvae

in soil samples Many nematodes exist, not all are bad Sample from top 4” of soil Follow sampling recommendations on suspect fields


Control of SCN No control method will eradicate SCN completely,

just decrease yield loss risk Prevent introduction of SCN – SCN can only move

few inches/yr on their own, may only move long distances on equipment

Crop Rotation – nonhost plants can decrease SCN population – high risk, 3yrs. Nonhost between SB

Resistant Varieties Nematicides – only one has proven effective Fertility – good fertility will decrease yield losses

from SCN Planting Date – Early planting can reduce yield

losses, roots develop before SCN becomes active


Tillage Soil should be smooth, somewhat fine to promote

quick emergence Avoid compaction that restricts root growth Type and amount of tillage has little effect, end result

is key Rhizobium Inoculation

Can help fix nitrogen more quickly Should be inoculated at planting time Consider if SB have not been planting in >5 yrs.

Unit 7: Major Agronomic Crops Wheat

Variety Selection Should be based on winter hardiness, standability,

disease resistance, yield potential Planting date has the greatest effect on winter

survival Yield potential usually >150 bu/ac

Usually not approached because of short grain fill period during high air temps in June

Ideal air temp at grain fill 68-76º Disease must be controlled to get high yields

Use resistant varieties and fungicides


Seeding Date Never seed prior to “fly-safe date”

Possible severe damage by the Hessian fly Best time is 14d period after fly safe date

Provides for ample growth before winter Reduces likelihood of disease infections

Seeding Rate Too heavy will increase lodging and disease

Decreases seed size Increases harvest lodge

Rates should be based on seeds/ft. of row rather than lbs/ac

13-20 seeds/ft of row recommended at normal seeding date


1-1.5 m seeds/ac is ideal seeding rate

Row Width 7” is common May be 10” to allow for residue movement >10” will decrease yields

Lodging Control Serious deterrent to high yields Apply proper N rates Select lodging resistant varieties

Increased lodging will increase incidence of disease Reduces straw quality Slows harvest


Disease Control Usually major limiting factor in yield potential

Losses can be 30-50% if no disease controls are used Correct diagnosis is key Select resistant varieties Plant well-cleaned, disease-free seed, treated w/

fungicide Plant in well-prepared seedbed after fly-safe date Rotate crops, never continuous wheat Plow down diseased residues Well-balanced fertility program

Top-dress N in the spring


Control grass Use fungicides only when necessary

Scout from flag leaf through flowering Head scab is a risk when no-tilling after corn

Same pathogen causing stalk rot and head scab Seed treatment should be used

Controls many diseases Protect young seedlings as they establish themselves

Fertilization N

Important step to high yields As N increases, risk for lodging and disease increases N needs may vary greatly depending on previous crop,

etc.


Each 1% organic matter provides 8-12 lbs N/ac Previous SB crop can provide 30-40 lbs N/ac

Spring N should be applied between Mar. & Apr. 15 Should be applied before spring growth starts to

stimulate tillering and promote larger head growth P

Soil P should be 90 lbs/ac or higher 1:4:2 ratio should provide good starter fertilizer

K Maintain soil level of 275 plus 5x the CEC for optimum

yields No-till Wheat

Smoot seedbed, proper seeding depth and date, absence of carryover herbicides, proper seed treatment


Normally follows SB in rotation Doesn’t grow well in poorly drained soils, especially

during wet conditions Major cause of stand loss is standing water Don’t no-till in fields that were harvested (SB) wet Spread soybean straw and chaff evenly so as not to

interfere w/ seeding Place seed 1” deep through residue

Seeds must be covered Slit must be closed

Exposure will decrease stands, disease, and injury Don’t drive too fast

Never exceed 5 mph


Disease severity decreases when tillage is removed from the production scheme

Reduces production costs, retains soil moisture Management

Determined by three factors Varieties genetic potential Management practices Environment or weather

All must be optimized to get maximal yields Steps to increased wheat yields

Highly productive and fertile soils High yield potential varieties Proper seeding time Proper seeding rates and stiff straw varieties


Adequate nutrient presence Control disease Scout weekly from April - June

unit 7: major agronomic crops chapter 17. unit 7: major agronomic crops unit 7 objectives: genetic...

Documents

major agronomic crops

major agronomic crops

major agronomic crops

major agronomic crops

soil conditions

yield potential slide

deeper slide

high planting populations