When to apply cover crops into soybeans

For some time I have promoted aerial applying cover crops into standing cash crops.  We have a pretty definitive maturity set for corn when it comes to aerial application.

But there is some question of when to fly cover crops into soybeans.  The range of discussion on this topic usually goes from 50% yellow leaf to 50% leaf drop.  The main goal from both viewpoints is sunlight reaching the soil to benefit the young seedlings.

To plant at 50% yellow leaf stage usually gains a farmer an extra 7-10 days of cover crop growth.  However, applying at 50% leaf drop assures better exposure to the sunlight for the seedlings.  I think that both options are excellent choices because I have seen both work very well. One thing we know for sure on the timing is that if the soybeans are still green over much of the field then the producer will have to wait for the beans to mature more.

This field was aerial applied on September 16. It was approximately 50% yellow leaf. The beans were planted in 7" rows. The cover crops in this field look very good.


Is it ever too early to apply when the soybeans are at 50% yellow leaf? Possibly – but when?

  • When planting into narrow rows (7-8″ rows) it seems that we might want to wait until the soybeans are more mature.
  • When there is great variation in the field.  It’s not uncommon to find “pockets” in the field that are still quite green when the rest of the field is more yellow.  When this happens I’d suggest waiting to apply until the vast majority of the field is yellowing. In the area where the soybeans are green there will be considerably less cover crop established.
  • If the soybeans are maturing earlier  and you are waiting for moisture (like in 2010) then waiting seems to make economic and agronomic sense. If it stays dry up until harvest then consider waiting until after harvest and incorporate the cover crops into the soil (by drilling or using a light “vertical tillage” after the cover crops have been spread).


Patience is often very rewarding.  Being patient to aerial apply cover crops into soybeans most often gives great rewards!



The left half of the photo above had been in 30" soybean rows. The right half had been beans in 7" rows. When aerial applying into soybeans planted in 7" rows be sure that the soybeans are around 75% yellow leaf and possibly at 50% leaf drop stage for the best establishment success.


This field needs to be more mature before aerial applying cover crops. In this situation the cover crop would be less likely to establish well.

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3 Responses to When to apply cover crops into soybeans

  1. Brian November 30, 2011 at 11:54 pm #

    Is there any concern with seeding so early such that it would interfere with harvesting the soybeans? Those cutting platforms don’t like green stuff, and it’s not ideal for the cover either I’m sure.

  2. Mark Gaerte December 17, 2011 at 11:07 am #

    Brian, from an aerial applicators standpoint, it seems some growers are jumping the gun on the timing of applications, I’m sure they all have many legitimate reasons and concerns, BUT…………we all want this stuff to work, I included! I have had a few have growers getting slowed down by the height or mass of the green stuff I’ve flown on for them. As far as the response from the cover itself I’d question Dave on this…..

  3. Dave December 17, 2011 at 9:55 pm #

    Hey guys, thanks for the comments and questions. I have heard of a few occasions where the cover crops were tall enough to interfere with harvest but that has been very rare. However when it has happened it didn’t matter how rare it was…it was a pain! I know of a gent in So. IL who had Hairy Vetch as tall as his soybeans at harvest one year. How did that happen? It rained plenty as the beans were nearing maturity and it did not stop raining for weeks. The temperatures were pretty warm and the moisture was plentiful and the light to the plants was decent too (between showers). I guess the biggest key is to get the cover crops planted “on time” and do your best to harvest on time as well.