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Soybean Row Spacing Results, And Another Palmer Amaranth Siting

Soybean Row Spacing Results, And Another Palmer Amaranth Siting

How did narrow row beans measure up this year? And what's the latest word on that new weed in Iowa?

Welcome to the tail end of October, says Clarke McGrath, in his latest online newsletter. He is the Iowa State University Extension field agronomist in western Iowa, based at Harlan. He's also a regular columnist each month in Wallaces Farmer magazine. Today McGrath reports: "We are either back in the field or will be shortly in most areas, so hopefully harvest will wrap up smoothly, although it is hard to tell how quickly it will go. Growers are finding that corn has sort of become stuck at grain moistures in the upper teens and low 20% grain moisture range--and this is bottlenecking transportation and storage issues. A warm spell would be welcomed right now, best of luck to all."

15" VS. 30" ROW WIDTH SOYBEANS: Soybean row spacing is a question that comes up continually. Investing in the extra equipment to plant narrow row soybeans isn't cheap, so farmers want to know they are getting the right return on investment from whatever row spacing they're in or may be switching to. "We've done and will continue to do row spacing trials in soybeans," says ISU agronomist Clarke McGrath.

"And by the way, high school fall sports playoffs will start this week, enjoy those if you get a chance." Clarke is a former referee for high school football games, now retired from that endeavor--but still going strong as ever as an agronomist. Here's what he has to say in his latest Extension crop production newsletter published a few days ago:

Cover Crop Field Days—Practical Farmers of Iowa has scheduled cover crop field days across Iowa this fall. Our southwest Iowa area field day will be near Stanton, on Mark Peterson's farm. That field day is set for November 14 from 1 p.m.-3:30 p. m. We will be starting at Mark's farm: 2311 N Ave., Stanton IA 51573. More info will be posted here as it becomes available, save the date and spread the word.

ISU FARM Plot: 15" vs. 30" row width soybeans—Soybean row spacing is a question that comes up continually. Investing in the extra equipment to plant narrow row soybeans isn't cheap, so farmers want to know they are getting the right ROI from whatever row spacing they are in or may be switching to. We have done and will continue to do row spacing trials in soybeans in our area about every year. You'll see more plot data as we get into the meeting season this winter, but this was my "best" row spacing plot and where I thought we'd see the biggest difference. Wrong. It will be fun to see how the rest of the plots turn out.~~~PAGE_BREAK_HERE~~~

We had a big plot south of Avoca, 5 replications on a high flat and down onto a B slope, looking at new varieties (2014 seed production for a major company). The 15-inch row width beans averaged 70 bushels per acre; the 30-inch row beans averaged 71 bushels per acre.

My cooperator had just bought a 50% larger planter and based on ISU data and local experiences decided to stay with 15-inch row beans so bought all the extra row units, drives, etc. that come with 15-inch row beans. When we did the math and gave him the results he had one word to say, which I cannot repeat here. On the other hand, last year we saw a nearly 3 bushel per acre advantage in the area for 15-inch row beans… so as we discussed it further we agreed that:

* We have a lot to learn about row spacing in soybeans (and corn for that matter)

* 15-inch rows still may very well have the long run yield advantage that Palle Pedersen found in his research

* We need to look at this continually since the variables--especially the seed varieties--change continually

* Knee high, green stemmy beans in September that look like they'll be lucky to make 45 bushels per acre and end up making 70+ are hard to argue about, no matter what the row spacing is.

Another palmer confirmation in Page County—The notorious weed Palmer amaranth, new to Iowa and first found earlier this fall in a couple of places, has now been confirmed in Page County in southwest Iowa. The exact location is undisclosed, but it's far from the previous finds in Harrison County and Eastern Iowa. This is just another reminder that we will want to step our scouting and weed management game up a notch or two. We'll get deeper into the Palmer Amaranth and weed control topics in winter meetings.~~~PAGE_BREAK_HERE~~~

Obscure weed found near Council Bluffs—Speaking of weeds, one of our local agronomists found some odd weed patches a few weeks ago and asked us for an ID. Bob Hartzler, ISU Extension weed management specialist, is pretty sure it's hophornbeam copperleaf, a southern weed never seen in Iowa before to our knowledge- Rich Pope, can you weigh in on this? Here is a University of Tennessee bulletin that describes it and some herbicides that are effective against it.

These weeds found near Council Bluffs were doing quite well in the crops and had escaped quite a few herbicides and spring tillage, so we will be on the lookout for this weed in other areas. Hopefully this is just an anomaly, much like the field pansy that causes some headaches in areas of Southern Iowa but doesn't seem to stray far from the areas we identified it a few years ago.

Fall Alfalfa-bloat and last cutting issues—I'll keep the bloat discussion really simple here… for more information on bloat I defer to Chris Clark, our ISU Extension livestock specialist. We have been getting questions on this topic as farmers start to turn cows out. Some of our concerns with frosted alfalfa--It used to be commonly thought that alfalfa didn't cause bloat after a killing freeze or light frost; this isn't true, in fact the risk of bloat can increase after a frost, killing or not, until the plant tissue is adequately dried out (think "baled hay" dry).

* When alfalfa is frosted, it breaks down cell walls and also increases the availability of some compounds that can increase the risk of bloat.

* Often our frosts coincide with guys getting adjoining fields harvested so they can get the cows off of the beat up summer pastures and onto cornstalks, and alfalfa that may be in the same fenced areas. While I am no "cow psychologist", experience tells me this seems to make the cows happy; they often enthusiastically hit the alfalfa pretty hard. So a little more bloat supervision/prevention can help guys steer clear of problems until the forage is dried out after a killing freeze.~~~PAGE_BREAK_HERE~~~

So while there is probably a slightly higher bloat risk for grazed alfalfa and white clover the first few days after a frost, if we follow normal bloat preventing grazing management when grazing alfalfa and clover, the risk can be mitigated.

The last cutting for hay—when should you take it? That's a hard question to answer. In a perfect world, we'd have enough hay for the winter stockpiled so we could leave the alfalfa standing for the winter--this is the best option for stand longevity. But, reality is we often need the tonnage so we have to take that last cutting. When to take it is the key to keeping a hay field healthier.

We tell farmers to try to wait for alfalfa to go dormant after a freeze before taking that October/November cutting. When is it "dormant"? It depends on whether the frost/freeze event was a "killing frost" or not. According to ISU's Extension forage agronomist Steve Barnhart, a "killing frost" for alfalfa is a roughly 23 or 24 F degree freeze that lasts for 4 to 6 hours or so. If the plants have been through a killing freeze like this, harvest ASAP. The longer we wait to cut and bale this hay, the more leaves and nutrition we lose.

A more common issue we get questions on relates to the "light freezes" or early fall frosts we have had. These are not as cold or as long in duration so they often just nip the tops of the plants. Alfalfa dinged by frost will try to keep growing--and using it's stored sugar reserves (which help with overwintering and spring growth, and ultimately contribute to stand life and tonnage)- so it is best to leave it alone until a true killing freeze hits, then hay it or graze it when it will no longer attempt to regrow (dormancy). With the drought stress on the hay this season, it may be even more risky than most years to try to take a late cutting before a killing freeze.

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