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Post by nathanp on Apr 3, 2013 16:35:19 GMT -5
If I am trying to grow multiple varieties of corn together in the same vicinity, but want to avoid cross pollination, how much do I need to stagger the planting dates?
Also, given that you harvest sweet corn at a completely different stage of growth than flour corn, how do you reconcile the day to harvest times across multiple varieties.
Example: 70 day sweet corn, 110 day field/flour corn Example 2: 70 day sweet corn, 85 day sweet corn
Just trying to figure this stuff out before I may mistakes...
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Post by Joseph Lofthouse on Apr 3, 2013 17:44:06 GMT -5
Flowering time of sweet corn is about 21 days before harvest. Flowering time of popcorn is about 55 days before harvest. So a 65 day sweet corn would flower at about 44 days, and a 100 day popcorn would flower at about 45 days. I'm writing Days-To-Maturity. I really mean Growing Degree Days Equivalent... In cold weather, it can take a month of calendar days to equal a week of growth in warmer weather. I consider it equal to a week of growth when the first planting is at the 3 leaf stage. Three Leaf Stage: Equivalent to one week growth in hot weather. The Ohio State University published a paper about Pollen Drift. It says that individual corn plants shed pollen for 5-6 days, but the field as a whole might take 10 to 14 days. It's based on planting highly inbred near clones. I figure the variation accounts for differences in soil and water in various parts of a field. If you are planting genetically diverse landraces flowering would last for a longer period. The same article also compares cross-pollination rates, and mentions a study that found cross-pollination rates were reduced by 99% at a distance of 40 to 50 feet.
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Post by RpR on Apr 5, 2013 14:21:47 GMT -5
You are going to have to take into account whether or not the corns come out of the ground at the same time or if one decides to come up a week or more later than it should ideally which means your planting time staggering is now totally out of whack.
I planted over six types of corn in close proximity last year, and the odd weather causing them to come out of the ground in a totally unpredictable manner making any pre-planning worthless, but at the same time, despite very close proximity, I had very little cross pollination.
That surprised me greatly but I did not have truly heavy winds till long after any pollination problems it could cause were long gone.
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Post by 12540dumont on Apr 6, 2013 13:27:34 GMT -5
I have found that I can reliably plant a 120 flint or flour at the same time I plant a 72 day Sweet without any crossing. The problem comes up is when I try to plant something in between these two dates. The corn on the left is a 72 day Sweet, the middle is a 120 posole, the right is an 85 day Sweet. Yeah, both sweets flowered at the same time. Putting them in the same bed always makes this happen. I don't know why. So, If I'm planning on doing something like this I don't put them in the same beds, I plant a block of 25 x 10 or 50x10 and I separate them by 50' (For me 25 x 10 is a good size for sweet corn). The other dimension I use for flint or flour. Attachments:
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Post by oxbowfarm on Apr 6, 2013 19:04:57 GMT -5
If you're growing corns other than modern varieties you should also consider if the earlier variety is likely to produce any tillers which would extend the pollen production period. Many Native American varieties tiller like crazy, Southwestern corns and Northern Flints especially.
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Post by nathanp on Apr 6, 2013 22:39:09 GMT -5
This is what I will be growing (the first 3):
Name Days to Harvest LISP Ashworth (Joseph's Breeding) SU-SU/SE-SE+ 60-65 day Paradise Sweet SE+ 70-80 day Joseph's Popcorn Popcorn 100-110 day
The tricky thing is that in one of the two fields I have access to, they will be adjacent to the following two: Sugar Buns Sweet SE+ Hybrid 70 day Oaxacan Field 95 (75-100) day
I just need to do the math based on when those other two are planted to minimize cross pollination. I am planning on planting one of the 3 there, and the other 2 in the isolated field with no other corn nearby.
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Post by Joseph Lofthouse on Apr 6, 2013 23:44:51 GMT -5
It seems to me like all of the sweet corn could go into the same field. That minimizes the risk of introducing non-sweets into the sweet populations, and makes timing easier... I really like timing by the growth of the previous patch of corn. It seems to work better than trying to time based off a calendar.
GDD calculations are great for timing. I figure 22 GDD per DTM, so a 65 DTM corn is harvested at 1430 GDD:50F. I like to download data from http:/DegreeDays.net into a spreadsheet. That lets me run scenarios. Growing Degree days accumulate very slowly on Long Island until about June 1st.
LISP Ashworth has the least se gene in it, and is earliest, so perhaps it would work well with the popcorn and Oaxacan green.
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Post by reed on Aug 23, 2014 6:38:31 GMT -5
The university report Joseph linked to on pollen drift is very encouraging. Based on it I have far less to worry about than I always thought. I can grow my corn (that I mentioned to Joseph before) and run two or three other corn experiments at the same time, even if they tassel together! My two small fields are about 400' feet apart and the big new one I'm borrowing from my neighbor is at least 600' feet from either one. It all is at least a mile to any other corn. One of my experiments is with a corn called Nuetta from Sand Hill Preservation. They say it is good in poor conditions, I can provide that. I'm going to mix it with some mid season types that have done well for me like Blue Jade, Hookers and Black Mexican. Then I'm going to throw in some extra early ones also from Sand Hill called Orchard Baby and Yukon Supreme. I'm going to pollinate them all with an early homozygous SE or two and see what comes out. I want to make a tough early sweet corn that has two or more ears per stalk and produces with out being watered as I have no good source to do so. Does anyone know of any other varieties I might throw into this mix? Thanks to all of you for the information and advice I find on this forum.
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Post by Carol Deppe on Oct 10, 2014 1:09:08 GMT -5
On isolating corn varieties by maturity times:
University information on the subject usually relates to strains or hybrids that are highly uniform and have highly synchronous pollen shed. It just doesn't apply to most op varieties.
In addition, corns maturity dates are usually listed as to the first ears. For many op corns, the harvest extends a month or more. So a "70 day" corn is really a "70 to 100 day" corn, and will probably overlap in pollination windows with a "90 day" corn. Most native American corns tassel out and shed pollen very nonsynchronously and over a very long period, a month or more usually.
My experience here in Willamette Valley Oregon, in spite of our huge frost free growing period, two timing-based isolation niches per season is the best I can do. Three may sometimes be possible, but takes luck and vigilance and extra work (such as getting out there and detasselling all late tassels off one variety as the first silks on show up on the other), and just can't be counted on. (The varieties will have better or worse soil fertility and other conditions, which can affect the speed of development enough so that one whole patch has to be eliminated after all the work of planting and growing it in order to save the others.) Even with just two crops, I also practice additional tricks. So, for example, I might plant a very early white flint and a very late yellow sweet corn. And use the rows where they come together as food. Then inspect the ears. With this combination, any crosses of the yellow sweet onto the white flint show up as obvious yellow kernels. And any crosses of the flint onto the sweet show up as obvious field type kernels in the background of wrinkled-kernel ears. Even so, there is enough overlap so that I also prefer to plant the late corn a couple of weeks later than the early corn. And it is important that the early corn does not go on better soil or get better fertilized than the late corn.
I plant only the combination of an early and a late. If I plant a midseason corn, I can't plant anything else. For this reason, among others, I'm much more interested in early corns and late corns and not particularly interested in midseason corns. And the late corns have to be ones that can be harvested after the rainy season starts, varieties that don't mold easily.
If I can't recognize crosses of the late corn onto the early corn, I can get around the problem by just saving seed from the biggest ears of the early corn. These will usually be the first ears on each plant, which are almost certain to have been pollinated before there was any overlap with the late variety. If there are crosses, they will be in the second or later ears. That also selects automatically for earliness in the early variety by makes it impossible to select for total yield in the early variety (which is what you get automatically when you save seed from all the ears).
If I can't recognize crosses of the early corn onto the late corn, I can get around that by walking the early rows and removing any late tassels before the silks on the later corn emerge. But that's work. And plenty of times it just doesn't get noticed and done at the right time. I prefer to set things up where I can recognize the crosses in at least one direction if not both as the backup plan whenever I isolate two corn varieties by maturity times rather than depending upon detasseling-assisted isolation.
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