by Jeremy Sweeten
The 2017 farming season was very tough on forage stands in the Midwest, especially the spring seeded forages. Numerous field visits clearly demonstrated the differences in field preparation.
Let’s dive into this a little bit. In the right year, just about anything will work when planting small seeds; however, in a challenging year, it pays to do a good job planting small seeds. Why? Because the failure rate can be quite high.
The most important thing is that small seeds need good seed to soil contact at the proper depth. The good contact allows the seed to absorb moisture, germinate, and establish roots into the soil. Seeding depth is just as important because small seeds need to germinate and start photosynthesis soon after emerging.
Most forage seeds don’t have the energy that a corn seed has. So alfalfa seedlings can come out of ¼” of soil, not 2” like a corn plant can.
Loose Seedbeds Cause Two Problems for Small Seeds
The first problem is uneven emergence due to poor seed to soil contact. Not all of the seeds will absorb moisture at the same rate, which will cause uneven emergence. Even worse is that they can’t absorb enough moisture to germinate. An uneven forage stand provides excellent areas for weeds to fill in the holes and take over. A thick seeded and growing stand of forages is a great form of weed control.
This chart is from Marvin Hall from Penn State. It is a chart referencing seeding depth compared to yield and emergence for birdsfoot trefoil. Notice - the deeper you plant, the less success you will have.
The other problem loose seedbeds provide is poor seeding depth. Ideally forages need to be seeded between ¼” to ½” depending on the soil type. Planting small seeds deeper than the recommended depth reduces the stand. This is due to uneven emergence or no emergence because the seedling runs out of energy before it can start capturing sunlight.
Should I Use a Disc or Harrow?
When seed is broadcast or planted with a conventional grain drill, some farmers talk about using a disc or harrow to “scratch” the seed in. I have yet to see a disc that can move ¼” to ½” of soil. Many times this action buries the seed too deep. A better alternative is a packer or a Brillion seeder. Conventional drills without press wheels work well with a packer pulled behind them.
Another common cause of a poor seedbed is the use of a rototiller. The tillers are very good at burying weeds and residue. However, they can leave the seedbed too loose. It is best to make sure to use a packer to firm the soil up after using the tiller.
What About No-Till?
No-till seedings work well if the forage seed can be placed shallow enough. Many no-till drills are made for larger seed placement, so special attention and setup needs to be done when planting forages. Get off the tractor and check seed rate and depth. Another key to no-till is effective, planned weed control. Too much residue will cause shading issues, hairpinning in the seed slot, and poor depth control.
A Few Rules of Thumb When Planting Small Seeds
- A firm seedbed is being able to walk on the soil and only sink in ½-3/4 of an inch.
- It is better to see 10-15% of the seed on the soil surface. That means you are not burying it too deep.
- If you can’t find any seed on the soil surface, shallow up the planting depth.
- Don’t just drive the tractor, get off and check out what is going on.
- Take your time, forage seed and lost time are both expensive.