Tractor Cultivation

“Cultivate” is a funny word. It’s used to mean, “to tend” generically. But it also means, “to tend your crops,” by killing the competition. This year, we have been cultivating more with our tractors. I have been wanting to write a post about tractor cultivation, but it’s something quite new to me and I don’t feel like I have enough experience with it to have anything worth saying…. nevertheless, a comment on a recent post has inspired me to, at the very least, chronicle what we are doing to kill weeds…

Something that’s clear to anyone who has had a garden, or even has met a gardener, is that weeds are generally despised. They compete with our crops for nutrients and water; they shade our plants and stunt their growth; they make the place look unsightly.

Clean beds are pretty

But, there are many reasons why weeds aren’t always so bad. The worst weeds on our farm, not by prevalence but by sheer awfulness, are thistles. Their spiny leaves hurt a lot when accidentally touched, even when they are small. Nevertheless, they are a refuge for ladybugs and ladybug nymphs, beneficial insects which feast on aphids… so thistles, they aren’t all bad. Yet, I wouldn’t be sad if I were able to rid them completely from my farm…

Now, the most effective strategies for keeping the thistle (and buttercup, and lambsquarter, and pigweed, and shepherd’s purse, etc) population in check don’t actually involve tractor mounted cultivators, per se: fallowing a whole field and stale bed cultivation. The easiest way to deal with weeds is when you can take a mower or a disk to an entire field that doesn’t have any crops growing in it.

One acre left fallow adjacent to an acre being planted. The truck in the background is spreading lime, to raise the pH of the soil – we spread 4400 lbs per acre!

This year, we have taken a few fields we used last year out of production. More than anything, we simply want to rest as much of the farm as we can, so our wonderfully fertile ground can stay that way. Yet, it’s also a really easy way to keep weed populations in check. The fields we’ve been fallowing were cover cropped last fall. This spring and summer, when flushes of weeds appeared amidst the oats and vetch, we simply mowed the whole field, setting back or killing the weeds, and giving the grass another opportunity to put on more growth. Similarly, we had a few new fields plowed this year, one of which we aren’t using until next year. Every so often, we take the tractor out there and disk in all the weeds that have germinated. It takes very little time and is very effective. Next year, we anticipate that field having fewer weeds…

For fields that we do intend to plant into, to the greatest extent possible, we try to use stale bed cultivation to control weeds. Whenever you work up soil, getting it ready to plant into, you are also creating a very hospitable environment for weeds. Weather permitting, we try to have a field we are planting into spaded three weeks to a month prior to planting. In that time, weeds will have germinated and started to grow. Right before planting, we make beds with our tiller, which does in most of the weeds that had appeared since the field was spaded.

Makin’ beds and killin’ weeds

Of course, in the lovely Pacific Northwest, the weather rarely is permitting. And for a good portion of our season, dry weather windows that allow us to work the ground are few. So, we frequently spade and till the same day or week, and we don’t get the opportunity to do that sort of stale bed cultivation. Now, it sometimes happens that beds get tilled and marked, but nothing gets immediately transplanted into them. By the time we are ready to transplant into one of these forgotten beds, if it has been colonized by weeds it gets a second tilling. One observation we’ve made, is that these beds are almost always the most weed free beds on the farm. For now, maintaining good soil structure is a higher priority than killing weeds, so we won’t be double tilling all our beds any time soon. But as with everything, there are always tradeoffs to be made and other possibilities to consider.

Our fall broccoli field – cover cropped, stale bedded, spaded, tilled, and ready for transplants this week!

Once crops are in the ground, it’s much harder to kill weeds because you don’t want to accidentally kill your veggies too. Larger, modern farms use herbicide and GPS guided tractors with 30′-wide cultivators.

Big tractor cultivating corn

But back before all that, commercial farmers used tractors with special weed-killing implements mounted in front of the driver to kill weeds. They stopped making these types of tractors in the early ’80s, but small-scale farms like ours still use them because they are the right scale for our sized farms. On our farm we have a Farmall Cub from 1951 and a Kubota 245H from 1984 that we use for cultivation.

Farmall Cub, about to cultivate winter squash, Mt Rainier and Kubota 245H in the background

I have a suspicion that the terminology for these tools might vary, but on the Cub we use what we call “sweeps” and on the Kubota we use what we call “knives.”

Sweeps, and lacinato kale flowers

Knives, and rainbow chard

Basically, sweeps are sharpened shovel blades mounted on the end of an adjustable shank. They throw soil in both directions. Knives are sharpened unidirectional wings on the end of a shank. They throw soil in one direction (mostly).

The sweeps are really nice to use because they don’t require so much precision. The shovels run down the middle between rows and are a good ways away from the plants, cutting a 6″ swath and throwing soil another few inches, depending on how deep in the soil you set them. You can go pretty quickly and not worry so much about killing your plants. They seem to work well with bigger weeds and grasses, but they aren’t especially accurate because they are fairly far from the crop. Because they throw soil, sweeps seem best suited to bigger plants that can stand having soil tossed on them, like transplanted brassicas, leeks and onions, corn, etc.

Siri cultivating brassicas with the Cub

Knives (or beet knives as they are sometimes called) only throw soil in one direction and only cut in one direction, so you can cultivate very close to your plants. Knives are best suited to plants you don’t want to bury such as lettuce, carrots, and beets when they are small.

In my limited experience, knives work really well when weeds are small and the soil is dry enough to flow around the blades. As soon as the soil is clumpy or weeds are big enough to get hung up on the blade, the knives start pushing soil onto the crop you are trying to cultivate and they don’t work nearly as well. It has also been my experience that getting the depth set just right really improves the outcome. On our farm, are fields are generally flat, but with many undulations and rolls. Our bedshaper does a pretty good job squaring up our beds, but it’s really obvious when one isn’t level when I’m trying to use the knives because it’s impossible to adjust the height of the knives accurately across the bed.

Rawley cultivating carrots

The act of tractor cultivation itself can be a bit like a crazy video game. Especially when you are using the knives, the plants, spaced every 8″ or 12″, seem to be flying by at a million miles an hour. If you could take your eyes off what you are doing for a second, you’d see that you are crawling up the bed at less than 1 mile per hour. It’s fun, and a bit stressful, especially because the third row isn’t visible from the driver’s seat. This is why it’s so important to have the rows in each bed be parallel with each other. As long as the knives that you can see aren’t killing the rows of carrots you can see, you can be pretty sure the knives you can’t see aren’t killing the carrots you can’t see. Nevertheless, I tend to stop every so often and check to make sure.

One last thought about these cultivation techniques – we invested in the Kubota this past winter for two reasons. One reason was that I was the only person on the farm who could reliably get the Cub started, so it was difficult to have anyone else do any cultivation (side note – the Kubota starts up every time, and after some wintertime maintenance, so does the Cub). The other reason is that the Kubota is built to use modern cultivation tools that you can buy at your local tractor store. Finding an inexpensive Farmall Cub or Super A is easy. They were some of the most popular tractors ever made. However, the Cub uses what’s essentially a proprietary system that was discontinued sometime in the 1960s. Finding cultivator parts for the Cub is an exercise in ebay frustration…. do you know how much it costs to ship hundreds of pounds of steel across the country? More than the parts costs. It is possible to have a local welder adapt the Cub’s toolbar to take the standard sized modern shanks and clamps, but that’s pretty expensive too. Sweeps and knives can be purchased relatively inexpensively from a tractor dealer. Farmall cultivators can be found on ebay, craig’s list, etc. But as far as I can tell, they never made knives. Whether knives are worth investing in, I can’t say. But I like having them because I like having options when it comes to killing weeds. Some crops like one cultivator over another, as do some soil conditions.

On that note, we also invested in a tine weeder this year.

The tine weeder, ready to tickle the weeds

We still haven’t used it much, but as our big fall plantings of beets, carrots, brassicas, and radicchio all go in this month, I think we’ll start “tickle weeding” all the beds pretty soon. The tine weeder, they say, works best when the weeds are at their “white thread” stage, meaning their root is just one thread-like radicle. The tine weeder agitates the soil, gently hitting your crops too, but the agitation is rough enough to uproot the baby weeds. One reason I bought the tine weeder, is that it’s an aspirational tool, meaning we’ll really have our act together when we can get at every bed with the tine weeder at just the right stage…. This aspect of the tine weeder is also the reason we haven’t used it much. But it’s something to aspire to.