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Serving: IN

Where Did All the Soybean Stubble Go?

Big wheels turn, soy residue lost.

From the looks of things while making windshield tours here and there across Indiana recently, it appears that the soil and water conservation folk need to bring back their slogan from the '90s: Don't till soybean stubble. Sometimes they characterized it by a red circle, with residue inside, and a big red 'X' across the middle.

Plenty of past soybean fields have been turned upside down. And while we've yet to actually see a moldboard plow out this season, either in soybean stubble or corn stalks, some of the jobs done on soybean stubble with chisel plows resemble moldboard plowing. We've seen some people running aggressive disk-coulter chisels across soybean fields.

After two decades of convincing evidence that you can either no-till into soybean stubble next spring or, if you prefer, work it once with a light tillage pass with a secondary tillage tool before you plant, the question is why till it now? Some of the fields were weedy- perhaps the farmer wants to cut up the weeds. We've seen one field where lime was going to be applied. Some agronomists can make a reasonable argument for working in lime with a tillage pass, particularly if it's level ground that's not subject to erosion as steeper fields. Remember, though, if you're using a chisel plow to incorporate lime or fertilizer applied this fall, that it only incorporates to about half the working depth of the tool. So if you're running the chisel eight inches deep, odds are you're only incorporating nutrients about four inches deep.

In some cases, there doesn't appear to be an obvious reason. Perhaps some think it will warm up quicker next spring- that's why several people are going to strip tillage, like Joe Rush, Walton. But only the area where the row will be is disturbed and tilled up. Lots of soybean stubble remains to cover the rest of the field. One of Rush' reasons for strip-tilling is to give the soil where the seed will go a chance to warm up and dry out a bit quicker next spring.

Perhaps weed control is another reason, that in tilling you prevent winter annual growth, but chiseled fields can still promote weed growth next spring. There are also fall herbicide options, many that could still be applied yet before the ground freezes, that would guarantee a cleaner seedbed next spring.

If the reason is just because harvest wound up early and they want something to do, it may be an expensive activity, with diesel fuel at super-high prices, and wear and tear on machinery commanding more in terms of dollars spent on repairs these days as steel prices rise. Trading for new equipment is also costly.

The best advice we've heard came from a farmer tilling corn stalks exactly one inch deep! His goal was to leave almost as much residue as was there originally. In some cases, especially when he ran on an angle, he actually left more of the surface covered by pieces of crop residue than where he didn't do anything at all. But his real goal was to level out the soil just a tad and also to start the breakdown process of crop residue by missing a very small amount of soil with the residue.

What he didn't want were rootballs and chunks of wet soil pulled up from deeper down to deal with next spring. The only thing worse than chiseling soybean stubble needlessly is tilling it wet needlessly. Time-honored stories that freeze-thaw will eliminate and problems with soil compaction in the first winter after the damage occurs are highly over-rated. Soil compaction created this fall could last several seasons, most agronomists conclude.

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