Pennsylvania Corn, Soybeans: Planting into Runaway Cover Crop Rye

Photo: Dave Wilson, Pennsylvania State University

Planting considerations

Questions from various growers have come in to different Extension educators around the state concerning planting into ryleage or cover crop rye that has gotten away and is now at a taller stage of growth.

I have planted no-till corn into short green cover crop rye, larger intermediate-height rye and in tall standing mature straw stage rye. Planting into the less mature stage rye and intermediate rye was “planting green”; planting into the taller straw stage rye was “planting brown.”

The shorter green cover crop rye is typically easiest to no-till plant into. We need to spray to kill the rye crop at this stage. At this stage and even up to about 12-14 inches of height we can spray first and then plant green or we can plant green and then spray, both methods work.

What about Rolling?

The main consideration about rolling is that we need to consider rolling to make the cover into a mat so that it doesn’t canopy over the small seedlings. With shorter green stands of cover crop rye we can get away without rolling because the immature green cover crop falls over and sort of “melts down” quicker after burn down causing less competition from shading. If the cover crop is taller and thicker then we need to consider rolling for management, every year is different.

Last year where we no-till planted green and did not roll it, our tall cover crop canopied over top of the small corn seedlings blocking the sunlight. We had a week or so of cooler weather and cloudy skies after the planting and this impacted the growth of the seedlings, (less sunlight and a canopy that fell over top of the corn seedling).

The prior two years we had nice sunny weather after planting and this was not an issue. So rolling gives us more physical control of the canopy.

If planting green 10 to 12 inches or smaller we can spray and roll or roll and spray. If planting green with a taller rye plant or planting brown with mature tall rye, we should consider rolling before planting and roll the cover crop down in the same direction of planting, make a flat mat to plant into. With taller Rye plants the rolling will prevent the canopy effect on the small corn seedlings.

When planting into a mature headed rye we can roll it and kill it, the plant as a winter annual after dehiscence is in the reproductive stage and it will dye on its own at this stage we don’t need to spray it to kill the plant. (We have done this on organic farms without herbicides) the rolling and crimping will kill the plant, It’s going to die anyway we are just helping it along and making a rolled mat of rye to plant into.

On conventional farms with the taller mature rye the herbicide consideration is that if we are using a preemergence herbicide we want to get that down to the soil level before we roll the rye. Sometimes, once we have a heavy rolled mat and we are spraying down on top of the mat of straw there can be some blocking that takes place.

AgFax Weed Solutions


What I’ve found is that the heavy mat of rye straw does suppress the weeds early on, in some situations for quite a while into the growing season. Eventually some weeds will break through the mat and then we may be able to hit them with a postemergence herbicide, but we need the right equipment to apply this depending on the timing of the weed breakthrough and the height of the corn. Usually this weed emergence occurs later in a field with a rolled down cover crop mat compared to a field with no soil cover which is open to sunlight.

Residue Management

For no-till planting considerations as we get into taller rye then the challenge becomes one of “residue management” and planting into the thicker mat of cover crop.

With the taller rolled down rye – having the right no-till equipment and set-up becomes paramount and this is the main concern for farmers planting into a heavier cover crop. If the grower doesn’t have the correct equipment and is not set up for this then its best to cut the standing rye get it off the field and no-till plant into the rye stubble.

Planting corn into smaller rye 12-15 inches or less, is more achievable. But if they are going to attempt no-till planting into the taller standing rye, here are some recommendations and considerations.

If there is a choice I would recommend no-tilling soybeans into the tall rolled down rye before planting corn.

This is because of rotation effect and less issues with available Nitrogen upfront early which is needed for the corn and not so the soybeans. A mature rye crop has taken out more nitrogen than a younger less mature rye crop. Also a less mature rye cover crop will decompose and give some of the nitrogen back sooner than a more mature lignified rye. Because of this if we are going to follow with corn we need to figure a full rate of starter fertilizer with enough available N to be available for the corn seedlings.

In the case if you have a rolled down rye mat on top of the soil, this doesn’t decompose readily so typically that is not a nitrogen tie-up concern. But the root mass of the rye plants can be. In the case of a rye stand that was planted as a cover crop we may have planted a bushel to a bushel and a half of rye (less than 100 lbs. per acre seeding rate) but in contrast If these fields are on dairy farms and were planted intended to be cut as forages then we typically plant as heavier rates, 120 -130 lbs. per acre some up to 150 lbs. per acre.

This means more plants per foot row which was intended for the heavier forage cutting which also gives us a much heavier root biomass in the top 2 to 4 inches of the soil (our corn planting zone) compared to a lower cover crop seeding rate root biomass. This heavy root biomass is unseen but the microbes will break it down and they require N to do that, initially if enough root zone N is not available we may see nitrate depression in the field in the critical early stages of growth of the corn.

So for corn an adequate starter fertilizer application needs to be applied here because forage planting rates of root biomass are typically much more than cover crop planting rates of root biomass.

With Soybeans this is typically not the same issue.

Also my experience has been that a long term no-tilled field with organic matter buildup is more forgiving than a shorter term no-till field. This is because the top 4 inches of soil are more active (we call this our soil health) and decomposition of the root materials takes place more efficiently as a result.

In some cases with planting corn after rye and after triticale I have seen an alleopathic effect (grass after grass) This is difficult to measure and varies year to year, also some of this is intensified if we have low levels of available N in the seed zone for seedling development.

For these reasons, I would recommend no-tilling soybean instead of corn. But No-tilling corn into rye, either green or a rolled down mat is achievable.

In either case no-tilling Corn or Soy, for tall rye or heavy biomass in the field.

1. Roll the tall rye in the same direction as you plan to no-till plant.

2. Ballast – Weight becomes an issue when planting into heavy mats

Older no-till 4 row planters typically aren’t designed for no-tilling into these heavier rolled down mats (especially dry rye straw) Comparatively legume mats (hairy vetch, crimson clover) are easier to cut into compared to straw rye, but still can be challenging.

Remember we are cutting through a rolled down mat above the soil surface and we are cutting through a significant root mass in the soil which hasn’t broken down, combined this can give us a lot of resistance.

On older 4 row John Deere Conservation planters you typically need to add weight. I’ve added 1 or 2 (90 lb.) suitcase weights on each of the planter units (In the insecticide box or mounted otherwise on the unit) to get enough ballast. On a 4 row Kinze planter we had 150 pound weights attached to each planting unit to give ballast.

With the newer and larger no-till planters with more row units we have heavier tool bars and we gain weight.

Some newer planters have hydraulic down pressure, some older planters have been retrofitted with rubber pneumatic units to give us adequate downward pressure on the planting units.

3. Aggressive wavy coulter units.

4. Row cleaners to move straw residue aside for double disk openers to follow and form a deep enough seed furrow.

5. Plant corn seed at two inches! We need to check this and adjust the depth gage wheels. The heavier the mat, the higher our depth gauge wheels are riding above the soil surface, and not cutting into the soil as deep because we are riding on top of the mat. We need to adjust the depth gauge wheels to make sure we are making our seed furrow deep enough. This is achieved by adjusting the depth gauge wheels and having enough ballast on the planting unit.

6. Seed firmers are recommended.

7. Finally, we need to achieve good seed to soil contact in the seed furrow.

Closing wheels: typically the lighter rubber coated closing wheels are not always aggressive enough to get a good seed furrow closing when dealing with a heavy cover crop residue or mat. This is a function of both ballast and design. We typically need a more aggressive closing wheel. In some cases we changed the rubber wheels with cast iron closing wheels, in some cases a dual finger closing wheel or dual shark tooth type closing wheels or one on one side and flat wheel on the other side.

Depending on the clay percentage of the soil and the moisture level under the cover crop we may cut open the seed furrow and have it left open as a V. We need to look carefully at this and make sure we are closing the seed furrow adequately to accomplish seed to soil contact. This open V seed furrow also can create an advantageous environment for slugs to stay cool and moist and I’ve seen them go right down the furrow below the soil surface level eating the corn seedlings.

 


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