1. Unit 7: Major Agronomic Crops Chapter 17

2. 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

3. 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

4. Unit 7: Major Agronomic Crops Temperature  Can survive brief adverse temps  Low ~32, high ~112  Growth decreases when temps are 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

5. Unit 7: Major Agronomic Crops  Latest planting date without much reduced yield June 15 th to July 1 st  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

6. Unit 7: Major Agronomic Crops  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

7. Unit 7: Major Agronomic Crops 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

8. Unit 7: Major Agronomic Crops  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

9. Unit 7: Major Agronomic Crops  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

10. Unit 7: Major Agronomic Crops 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

13. Unit 7: Major Agronomic Crops 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

14. Unit 7: Major Agronomic Crops  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

15. Unit 7: Major Agronomic Crops  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”

16. Unit 7: Major Agronomic Crops  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

17. Unit 7: Major Agronomic Crops  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

18. Unit 7: Major Agronomic Crops  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

19. Unit 7: Major Agronomic Crops 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

20. Unit 7: Major Agronomic Crops  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

21. Unit 7: Major Agronomic Crops  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

22. Unit 7: Major Agronomic Crops  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

23. Unit 7: Major Agronomic Crops  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

28. Unit 7: Major Agronomic Crops 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.

29. 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

30. Unit 7: Major Agronomic Crops 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

31. Unit 7: Major Agronomic Crops  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

32. Unit 7: Major Agronomic Crops 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

33. Unit 7: Major Agronomic Crops  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.

36. Unit 7: Major Agronomic Crops  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

37. Unit 7: Major Agronomic Crops  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

38. Unit 7: Major Agronomic Crops  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

39. Unit 7: Major Agronomic Crops  Adequate nutrient presence  Control disease  Scout weekly from April - June