Soybean Yield Management and Physiology Comparison To Corn

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Soybean Yield, Management and Physiology: Comparison To Corn North Central Branch, ASA March 16

Soybean Yield, Management and Physiology: Comparison To Corn North Central Branch, ASA March 16 -17, 2005 Emerson D. Nafziger Crop Sciences University of Illinois

Outline for Today • Current status of soybean yields • Yield physiology • Weather

Outline for Today • Current status of soybean yields • Yield physiology • Weather interactions • Management issues • Summary and “proposal”

Corn and Soybean Acreage in Illinois, 1990 -2004

Corn and Soybean Acreage in Illinois, 1990 -2004

For Soybean Yield, How High is “High”? • R. Cooper (in IL and OH)

For Soybean Yield, How High is “High”? • R. Cooper (in IL and OH) reported over 100 bu in subirrigated semi-dwarf types • 300 K seeds/acre in 7 -in rows • The reported world record (Ray Rawson) is 118 in MI • 100+ bu/acre in county strip test in NW Illinois in 1990 on a “virgin” field • Highest county average yield was 57 bu/acre in 1998 in Jo. Daviess County and in 2002 and 2004 in Carroll County, both in NW Illinois • Highest yield in the UI variety trials was 82 bu/acre at Perry in 2004 • Highest Illinois state avg yield is 50. 5 (2004)

Why Not Higher Soybean Yields? • A partial list, compared to corn: • Soybean

Why Not Higher Soybean Yields? • A partial list, compared to corn: • Soybean has ~50 percent higher energy content per lb of seed and 7% heavier bushels than corn • It does photorespiration, losing up to 1/3 rd of photosynthesis to this “useless” process • It fixes some of its own N • It fills rapidly for ~30 days v 45 -50 for corn • More sensitive to air pollutants(? )

Yield v maturity date, Reg. 3, MG 3 RR, 2004

Yield v maturity date, Reg. 3, MG 3 RR, 2004

Yield v maturity date, Reg. 3, RR, 2000

Yield v maturity date, Reg. 3, RR, 2000

Soybean Yield Physiology • The ability to maintain high photosynthetic rates throughout seed filling

Soybean Yield Physiology • The ability to maintain high photosynthetic rates throughout seed filling stages defines high yield potential • Among C 3 crops, soybean has relatively high photosynthetic capacity • The maximum sustained seed fill rate is ~3 bushels per day • This fill rate sustains for ~30 days under normal temps; can be longer if cooler • By far the largest reason for decreased Ps causing lower seed fill and yield is inadequate water

A Mystery of Soybean Yield Physiology • There is no clear indication whether soybean

A Mystery of Soybean Yield Physiology • There is no clear indication whether soybean is “source-limited” (inadequate Ps) or “sink-limited” (not enough places to accept Ps products = sugars) • This “confusion” may be of minimal importance as long as breeders can maintain progress, but it’s still of interest in the field

Evidence for Source Limitation • Increasing CO 2 in the atmosphere increases yields (Soy.

Evidence for Source Limitation • Increasing CO 2 in the atmosphere increases yields (Soy. FACE & others) • Ozone & other pollutants reduce yield • Defoliation reduces yield, if it’s severe enough • Drought reduces yield, often by reducing seed size

Evidence for Sink Limitation • Removing some leaves increases Ps rate in remaining leaves

Evidence for Sink Limitation • Removing some leaves increases Ps rate in remaining leaves • Pale green (low chlorophyll) mutants yield more than Ps rates would suggest • Leaves accumulate starch during the day; inability to utilize sugar fast enough? • Adding N fertilizer (low fixation) fails to increase yields

“Practical” Yield Physiology • With exceptions, soybean plants initiate enough seeds for high yields,

“Practical” Yield Physiology • With exceptions, soybean plants initiate enough seeds for high yields, but may fail to adequately sustain pods or fill seeds due to reduced Ps during critical stages (R 5 -R 6) • Canopies and leaves are usually adequate, but root systems often fail to provide enough water to maintain Ps • With potential seedfilling rates of 3 bu/day, reductions in Ps for even short stretches in August hurt yields • Starting to fill seeds slightly earlier or extending seedfilling slightly longer can increase yields greatly

Soybean Reproductive Development R 1 R 2 R 3 R 4 R 5 R

Soybean Reproductive Development R 1 R 2 R 3 R 4 R 5 R 7 R 6 R 8 Seed Filling Pod Development Flowering Indeterminate Growth Vegetative Growth 0 10 20 30 40 50 60 70 Days after flowering ©Palle Pedersen

Seed and Pod Development R 5 R 6 R 7 (1) R 8 (all)

Seed and Pod Development R 5 R 6 R 7 (1) R 8 (all) ©Palle Pedersen

Soybean management goals: • To enable to crop to take full advantage of good

Soybean management goals: • To enable to crop to take full advantage of good weather when it happens • To protect the yield of the crop, at least partly, from disastrously low yields when the weather is poor • In practical terms, we need to “position” the crop for maximum seedfilling rates

Planted Apr. 5 Photo May 24

Planted Apr. 5 Photo May 24

Planting Date & Rate ave. 9 No. IL sites, 2001 -03, mid-maturity, 4 seeding

Planting Date & Rate ave. 9 No. IL sites, 2001 -03, mid-maturity, 4 seeding rates

Effect of Planting Date on Maturity and Plant Height (response to day length) Planting

Effect of Planting Date on Maturity and Plant Height (response to day length) Planting Date April 11 Maturity Date Sept. 16 Plant Height-in. April 24 Sept. 17 30. 5 May 11 Sept. 22 31. 6 May 29 Sept. 28 33. 2 Monmouth 28. 9

Planting Date and Seeding Rate Data from J. Gander, Pioneer Hi-Bred

Planting Date and Seeding Rate Data from J. Gander, Pioneer Hi-Bred

Planting Date and Seeding Rate University of Illinois

Planting Date and Seeding Rate University of Illinois

Planting Rate and Variety Data from J. Gander, Pioneer Hi-Bred

Planting Rate and Variety Data from J. Gander, Pioneer Hi-Bred

Seeding Rate and Row Spacing E. Adee, University of Illinois

Seeding Rate and Row Spacing E. Adee, University of Illinois

Seeding Rate and Row Spacing P. Pedersen, Iowa State Univ.

Seeding Rate and Row Spacing P. Pedersen, Iowa State Univ.

Seeding Rate Economics ↑ Optimum University of Illinois

Seeding Rate Economics ↑ Optimum University of Illinois

Variety Maturity & Planting Date, 2001 -03

Variety Maturity & Planting Date, 2001 -03

Planting Management • 100, 000 plants per acre is enough to maximize yield, if

Planting Management • 100, 000 plants per acre is enough to maximize yield, if they’re all healthy and evenly distributed • Variety, varietal maturity, row spacing, and planting date don’t seem to affect seeding rate/plant population response much • Good quality soybean seed responds little if any to seed fungicidal seed treatment or inoculant • Planting in the first half of May is appropriate for soybean, with little loss 1 -2 weeks on either side of that period

According to Some… High corn yields are an accomplishment While High soybean yields are

According to Some… High corn yields are an accomplishment While High soybean yields are an accident

Now We Know Better! • Still, it’s clear that managing soybean within our weather

Now We Know Better! • Still, it’s clear that managing soybean within our weather and soils will disappoint sometimes • But, the US remains a good place to grow soybeans, and with continued attention to genetics and inputs, we can continue to compete

Seedfill Monitoring in Soybean • As a pilot in 2005, we are going to

Seedfill Monitoring in Soybean • As a pilot in 2005, we are going to take weekly samples of soybean pods from 25 -30 plants • Dry and thresh to determine seed wt per plant • Relate ΔDW to temperature, moisture, and solar radiation during past week • Care to join us? [email protected] edu

Thank You

Thank You