The following publications should help answer any questions
What is in these papersMost farmers are not seeding at optimum seeding rates even considering high hybrid seed costs Early varieties needs high populations in narrow rows for maximum yield.
Silage corn yields under very high populations, although quality declines somewhat
Early varieties can avoid some drought Lack of moisture is the most limiting yield factor on most corn acres
Plant spacing is not important at high populations. (This allows faster seeding, as well as use of other planter and seeder equipment)
Maximum grain yield is already occurring under ideal corn yielding conditions. Light becomes the limiting factor under these conditions. (Despite hype from corn companies, there is a real limit to yields. Average future farm yields of 300 bushels per acre is highly unlikely)
Corn has highest evapotranspiration of any crop
Early maturing corn can avoid the corn borer
Population and Plant Densities
1
Yield Response of Corn to Crowding Stress. http://agron.scijournals.org/cgi/content/abstract/97/3/839Plant competition between the periods of vegetative stage (V5) and anthesis and anthesis to early grain filling had the greatest effect on grain yield.
2
Row Width and Plant Density Effects on Corn Grain Production in the Northern Corn Belt. http://agron.scijournals.org/cgi/content/abstract/94/5/1020Narrow rows and highest plant populations had the highest yields.
3
Corn Plant Density…. Where we‘ve been and where we’re going www.uwex.edu/ces/crops/CornPlantDensity04.htmCalls for higher corn populations.
4
Corn Maturity and Ensiling Corn http://www.ag.ndsu.nodak.edu/dickinso/agronomy/cornmaturity.htmInfo on corn development
5
Plant Population Effects on Silage Yield www.pioneer.com/web/site/portal/menuitem.7d750b63e7394ade3c3d48e7d10093a0/Shows higher yields at very high populations, but quality decreases
6
Corn Hybrid Response to Plant Populations www.pioneer.com/web/site/portal/menuitem.d329704b991fbeac81127b05d10093a0/Figure showing that yield narrow between early and later hybrids as plant populations increase
Graph showing lodging under different population (Scroll down to figures 4 and 5)
7
Higher and Lower Planter Rates www.pioneer.com/web/site/portal/menuitem.8da514bd9c4d58de3c3d48e7d10093a0/Shows planter rate income advantage with under adequate and short moisture conditions
8
Hybrid Switch Decisions www.agriculture.purdue.edu/aganswers/story.asp?storyID=575Corn Maturity and Drought
9
Evaluation of the Adoption of Ultra-short Season Corn for the Mid-south. www.ag.auburn.edu/nsdl/sctcsa/Proceedings/1999/Keisling_b.pdfIdea was to avoid summer drought. Concluded narrower rows are necessary.
10
Drought Tolerance www.pioneer.com/web/site/portal/menuitem.3788e12c5693c2444cfe78e1d10093a0/Map of U.S. shows average yield loses due to drought
11
What Happens Within the Corn Plant Under Dry Conditions www.uwex.edu/ces/ag/issues/drought2003/corneffect.html12
Evapotranspiration of Corn http://www.cprl.ars.usda.gov/wmru/pdfs/96et_corn.pdfCorn (Zea mays L.) has one of the highest evapotranspiration (ET) rates of all the irrigated crops
Corn Yield Potential
13
Calculation of the rate and duration of grain filling in corn http://crop.scijournals.org/cgi/content/abstract/12/4/48590% of grain filling accumulated linearly beginning 2 ½ weeks after silking
14
Ohio Agronomy Guide http://ohioline.osu.edu/b472/Early to mid-maturing hybrids have been developed in recent years with yield potential approaching full season hybrids.
15
Post-Green Revolution Trends in Yield Potential of temperate Maize in the North Central United States. http://crop.scijournals.org/cgi/content/abstract/39/6/1622The author suggest maximum grain yield has already occurred as yields of corn contest winners have not increase over the past 25 years. Average yields are increasing as breeders are developing hybrids better able to withstand stress.
16
Adaptedness and Heterosis in Corn and Mule Hybrids http://crop.scijournals.org/cgi/content/full/46/2/528Duvick's (1999) regressions for actual rates of gain per year for yield favor the larger, higher yielding hybrids; however, the smaller, lower yielding inbreds gain faster in percentage of gain for yield. If the trends in percentage of gain continue, inbreds that yield more than hybrids may occur within the present century.
17
Forage Yield and Quality of Corn Cultivars Developed in Different Eras http://crop.scijournals.org/cgi/content/abstract/41/5/1449Since 1930 forage, stover, and ear yield have increased 1.4, 0.7, and 2.4% yr-1, respectively.
18
300 bushels of Corn……When and How www.ipm.iastate.edu/ipm/icm/2007/2-12/300bpa.htmlYields under optimum conditions have not increased … 300 bushels highly unlikely
19
Vegetable and Corn Yields in the United States, 1900-Present http://www.hort.wisc.edu/Goldman/Web%20Pages%20New/cropyield.pdfYou may find this paper interesting. Potato yields and increased seven fold since the 1930’s almost entirely due to environmental factors, mainly nitrogen fertilizer and irrigation. We know this because most of the production had been with the russet potato, developed over 100 years ago. Alfalfa yields have not increased at all, nor has any legume forage crop as there is no nitrogen response and the entire top growth is harvested. Corn yields have gone up five fold, but corn silage tonnage half of that.
Plant spacing - Drills and Air Seeders
20
Plant Spacing www.pioneer.com/web/site/portal/menuitem.268d86162ece78de3c3d48e7d10093a0/Research confirms benefits of improved plant spacing except at high plant populations. (Paragraph under figure 1)
21
Response of Drilled Early Corn to Several Plant Populations.www.oznet.ksu.edu/library/crpsl2/SRL116.pdf
This paper is about early maturity corn drilled in 7 or 6-inch rows at 4 location in Kansas. Highest yields were at 80,000 plants per acre. 85, 95, and 105-day hybrids had similar yields, but the 75-day hybrid had considerable lower yields. I suspect the poorer yields of the 75 day hybrid due to poorer genetics.
22
Air Seeders http://www.topcropmanager.com/content/view/873/38/Information on seeding with air seeders in Canada. Don’t worry about plant spacing when planting silage and grazing corn
Miscellaneous Pertinent Subjects
23
European Corn Borer http://entomology.unl.edu/ecb/ecb1.htmAn early maturity corn will have significantly fewer borers. (also adult beetles) scroll down to CULTURAL CONTROLS and then Maturity group
24
Quantitative Trait Loci Controlling Leaf and Tassel Traits in a B73 x Mo17 Population of Maize. http://crop.scijournals.org/cgi/content/abstract/42/6/1902Discusses light availability - effect of tassel and upright leaves.
25
Understanding Green Snap www.uap.com/profprod/docs/Understanding%20Green%20Snap%20in%20Corn.pdf26
Pioneer Locations27
Crop Watch28 Using corn maturity to maintain grain yield in the presence of late-season drought
29 BMR Corn Silage