Unit 7: Major Agronomic Crops

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 <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

5. Unit 7: Major Agronomic Crops • 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

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