The cool weather continues, maybe just to spite us for featuring NOAA’s September forecast calling for warmer than typical temperatures.
Decisions moving into fall
As cool nights roll in, many of our crops start to slow down. Knowing when to pull a crop out of the field or high tunnel can be a tough decision, but having a plan for what will be planted next can help. Do you want to keep the season going with fall and winter crops? Do you want to plant a cover crop for soil fertility? In our crop updates below, we’ll discuss considerations for when it might be time to remove each crop to make space for the next thing.
What can still be planted this time of year?
In a high tunnel, September is a great time to plant:
- A short-season lettuce crop for harvest in November
- A winter spinach crop, which will grow and establish throughout the fall, slow down significantly over the winter, and then pick back up in late winter / early spring for harvest around March.
In the field, there’s still time to plant a quick fall crop like radishes or a cold hardy lettuce. This is also a great time to plant a cover crop to keep your soil covered through the fall (and potentially winter if you choose something that will overwinter), and potentially give you some nitrogen.
Flipping beds
There are many ways to “flip a bed”, or remove residue to make way for the next thing. We held a field day in the campus high tunnel yesterday where we explored some different approaches to bed flipping.
One goal should be to minimize tillage as much as possible in this process. If you learned farming or gardening from your parents or grandparents, tilling in the fall might be very ingrained as the standard way to end the season. However, in our 100 farms project (confirmed by many other research projects on soil health), we learned that every tillage pass counts against soil health. Farms with less tillage had healthier soil: they had better aggregate stability and structure, and more organic matter. So, what are some ways to deal with residues at the end of the season?
- Mowing residues: A flail mower is my #1 favorite tool on a vegetable farm. Flail mowers chop residue into fine pieces, and do a good job of leaving residue in the same spot it came from vs. throwing it all over the place. Chopping residues helps them to break down quickly. In some cases it’s appropriate to leave the residues right on the soil surface as a much for the winter. If you’re trying to seed a cover crop, you may need to incorporate residues with some tillage to help them break down quickly and to get a nice, smooth seedbed.
- Tarps: If you have a crop that needs to be killed, and mowing won’t kill it (e.g. many cover crops), you’ll need another way of killing the crop. Tarps can be a great option for blocking light, thereby killing the crop. Many farmers combine mowing with tarping. Mowing the residues down makes it easier to put a tarp over the field, and having the leftover residue already mowed and chopped makes for more manageable residues after you pull the tarp up.
- Tilling: While we generally should be reducing tillage, tilling a field at the end of the season is a good way to incorporate residues for faster breakdown, and to get the soil ready with a smooth seedbed for the next planting. For plots with a lot of residue, mowing before tilling can be helpful.
A comparison: Two weeks ago, the Grossman lab team flail mowed a very robust cover crop stand in the campus high tunnel. They tilled one half (on the left in the photo), and tarped the other half (on the right in the photo). We were surprised to see that after two weeks, the two sides looked pretty much the same, and the half with the tarp had a lot more soil moisture (this is a good thing). They ran a shallow tillage pass over each bed, and the side that had been previously tarped was actually in better shape to plant directly into than the side that had been tilled two weeks ago. The tarp conserved soil moisture better than the tilled side, making the soil softer and easier to work with. The soil was still tilled, but the tarp allowed us to cut out a deep tillage pass.
 | |
| The left half of the bed was tilled two weeks ago, the right half was tarped. Both were then tilled at a shallow depth to prepare the seedbed for planting. |
| There was another bed in the tunnel where we had been growing cucumbers. The weeds were managed very well in this bed thanks to a weekly pass with a wheel hoe, and when we pulled the cucumbers, the beds were pretty much residue free. We did bring a sprinkler into the tunnel about a week before we planned to plant our fall crop. The cucumber bed just had one line of drip tape, and the soil had become bone dry outside of that thin line of irrigation water. Overhead watering helped to make the soil softer and more easier to manage. |
 |
| Cucumber bed after removing residues and doing a shallow tillage pass for seedbed prep |
Crop Updates
Cucumbers
If temperatures dip down into the 40s cucumbers will be done. Even in high tunnels, cucumbers are starting to slow down significantly. The deciding factor for when to pull them may be a back-of-the-napkin calculation about the value of your labor. Two weeks ago you may have been packing 2 boxes of cucumbers per row, and now you’re picking about ½ box. How much time is taking you to find cucumbers each week, and how much are you charging for them? At some point, the return just isn’t there. Other times, cucumbers can become so overrun with aphids, whiteflies, or disease that it’s better to just pull them.
Melons
We are hearing reports from Iowa that the watermelon harvest wrapped a month and a half earlier than usual, due to wet weather. The calculation on whether to hold out hope for a few more melons is the same as cucumbers. How much time are you spending looking for lingering melons? As the nights get colder, melons will show clear signs of being done for the season.
Pumpkins and squash
The cool week ahead will likely get some people in a fall decorating mood, hopefully early harvested pumpkins and squash can find homes.
A common question during this time of year is what to do about powdery mildew. If you are seeing widespread powdery mildew, it isn’t the right time to use fungicides. Fungicides are preventative in nature, and would have worked to slow the disease down when you found your first white spot a month or two ago. As fields get defoliated, try to get pumpkins in the shade to prevent potential sunburn.
If you have been doing sprays for powdery mildew, those can stop three weeks before harvest.
Radishes
The first successions of fall radishes are coming in, and there’s still time to plant another succession of quick to mature radishes and / or turnips. Watermelon radishes are particularly popular for fall / winter harvest.
Spinach
The time to plant winter spinach in high tunnels is approaching. Generally mid to late September is a good time to plant spinach that will be harvested in the spring. Johnny’s has a number of varieties that are specifically bred for overwintering.
Tomatoes
Just as tomato production is really catching up after a slow start to the season, the cool nights will begin to slow down tomato fruit development. Tomatoes are generally worth leaving in the field until they succumb to a hard freeze. If there is a freeze in the forecast, harvest everything that has begun to turn red, as these fruits will slowly ripen off the vine. In a high tunnel, this calculation is trickier, especially if you hope to plant winter spinach, fall lettuce, or a cover crop in the rows where you currently have tomatoes. The thing is, as temperatures get colder, tomato ripening really slows down. We definitely have a few good weeks of production left in high tunnels, but as September ends, the value of keeping tomatoes in the ground becomes more questionable. Just like in the field, you can harvest your unripe tomatoes before pulling them. If you heat your high tunnel, your tomatoes should survive and produce well into October as long as foliar disease is under control.
Let us know if these updates are helpful!
Comments
Post a Comment