It's not for the faint of heart
Going no-till certainly has been picking up steam in recent years, and overall it’s a good thing. When I first got involved in viticulture back in 2010 I was living in Italy. Like a lot of Medditerranean viticultural areas, there was a tendency to disc everything all the time. If you didn’t have a barren wasteland with vines poking out of it, you weren’t a good farmer. Anything you couldn’t get to with a tractor you sprayed with herbicide. One of my first vineyard jobs in Italy was spraying glyphosate out of a backpack sprayer all spring. I felt like I was in the final scene of the Godfather! Minus the dying part.
Herbicide: the new four-letter word
Mentalities have shifted since then both in Europe and here in the states. All in all it’s a good shift. We’ve all seen places that have gone on for years and years using herbicide to a point where you don’t even need to spray it anymore because that soil is so dead. The only thing that grows on it is that weird reddish moss.
Percolation suffers. The soil forms a crust on top and water can’t infiltrate it. You’ll walk these vineyards and you see the water from the emitter just beads up and drips off the berm like Teflon. Then it pools in the tractor row. There is just no porosity to these soils and it makes irrigation almost impossible.
Aside from that, herbicides are gross. We’re lucky in vineyards to not use too many nasty chemicals but the ones that are nasty are all herbicides especially the pre-emergent ones.
Herbicides also have developed a bad rap among consumers especially roundup or glyphosate, which is ironic because it really isn’t that toxic compared to others. As an aside, there are a bunch of people out there who seem to think that glyphosate is the same thing as Agent Orange. For the record that is very not true. They are completely different chemicals. Commercial forms of glyphosate can be orangey in color. The resemblance ends there.
The trouble with tilling
Conventional tillage can also be problematic. Frequent tilling destroys soil structure. If you break a chunk of undisturbed soil apart, you’ll find that it breaks into aggregates of soil particles. Inside those aggregates you’ll find different sized pores, both big ones that hold air and tiny ones that hold water. Plants need both of these things to thrive. The aim of tillage is to break these aggregates up into smaller bits but long term that is going to negatively affect your plants.
Tillage also leads to compaction, again over time. Then the only way to break it up is with more tillage. It’s like one of those vicious things!
No-till coupled with covercropping helps build soil structure improving water-holding capacity and aeration of the soil by way of better porosity. It does this at the same time as it builds organic matter. Organic matter is a source of nutrients for the vines. Everything contained in the plant decomposes and becomes available to the vine. This is particularly important in the case of leguminous covercrops that fix nitrogen. Organic matter has a negative surface charge and so it holds onto all the positively charged cations your vine needs namely Ca, Mg, and K.
The breakdown of old plant matter into organic matter is driven by microbes and this is what people mean when they talk about the “living soil”. Herbicides and tillage disrupt the lifecycles of soil microbes and limit their ability to do this. No-till is supposed to leave these little guys alone to do the work we need to free up nutrients and make them plant available. In theory anyway.
Mismeasure of microbes
I say in theory because this is really hard to measure. I think this is one of those areas where agriculture lapses into the religious. Basically, it’s a hard thing to sample for and we see this all the time sampling for nematodes. You may have one pocket over here that has this number of some kind of microorganism and a few feet over you have a different one. It’s hard to establish scientifically that one tillage treatment or another favors diversity of microorganisms or how numerous they are. Many of the papers out there come up inconclusive even if it makes total sense that if you mess with something’s environment they aren’t going to thrive as much as if you left it alone.
But there are some shining examples of work that support this idea. Chen et al. found that conservation tilling (i.e. no till and reduced till) increased total soil microbial biomass by 37% at least in the top 8” of the soil. They found that this only worked in loamy soils, and that sandier or coarser textured soils didn’t see the same effect. This is mostly because you need higher levels of soil carbon and sandy soils don’t have a whole lot of that. It showed what we expected that fewer disturbances allowed for more efficient use of that soil carbon. Basically, the microbes did a better job breaking things down if you didn’t run a plow through their house every couple of months.
Nunes et al. is another paper that explored this topic. They looked at seven different indicators for soil health:
- Soil organic content
- Microbial biomass carbon, which is a measurement of carbon contained in the living portion of the soil i.e. microbe bodies
- Nitrogen
- Soil respiration, which is proxy for microbial activity
- Active carbon, which is the carbon that is available to the microbes
- Beta glucosidase, which is the enzyme involved in the degradation of cellulose (plant bodies)
- Soil protein, which is the soil’s ability to store nitrogen
They found that every one of these measures was improved by reducing till. Again, this is usually something we see only in the top portion of the soil (top 8”).
The bigger picture
Now neither of these studies are on vines. If you’re looking for some reading material on no-till in vineyards, Richard Smart from UC Davis did some incredible ahead of his time work. I urge you to take a look at some of his papers. This one in particular puts no-till into the context of global warming, which if anything, is the real reason we all should be looking at moving in this direction.
Bottom line is that untilled land sequesters more carbon than tilled. ½ of all the carbon in the atmosphere is estimated to come microbial respiration of carbon on the surface of the soil. A lot of this comes from the large-scale repurposing of land that has occurred over the last 200 years. All nitrogen (nitrous oxide is also a greenhouse gas) comes from microbial activity on the surface of the soil.
Covercrops alone don’t help the problem. Yes, the covercrop sequesters a lot of carbon but if you then till that into the soil, the benefit is lost. All that carbon gets released and it gets released quickly.
This is a great study. They looked at one vineyard over seven seasons and found that going no-till sequestered 1.5 metric tons per acre. It also increased the oxidation of methane which is good even though that technically increases CO2. Methane’s global warming potential is 27 times that of CO2 so less methane is a good thing.
This study also took into account fuel burned up during tractor passes as well as N20 production. No-till is net negative. Even going to occasional tilling tipped the scales not just because it released sequestered carbon, but also just because it meant another tractor pass.
The limitations are numerous
From a practical standpoint, what does it mean to go no-till? The first limitation we face is that, you have another plant whether a covercrop or a weed, that competes with your vine for water and nutrients. This is going to be a lot more severe if you are going wall to wall no till i.e. where you leave the undervine row untilled as well. Most growers we work with if they do go no-till opt for just leaving the midrow or the tractor row untilled. Leaving the undervine untilled is a whole lot harder.
A lot of the studies that are out there on no till point out that going no-till significantly reduced yield in whatever crop they were working on. Grapes are a little different since, if you’re a fine wine maker, yield may not be your main target. Some of the growers I’ve spoken to about their experiences say that in the first year they noticed stunted growth. Keep in mind that the cover crop is growing in the spring, right when your shoots are trying to develop. It’s the worst timing, but there’s not a lot you can do about it. This is of particular importance in climates with wetter winters. In those cases, there’s a lot of spring nutrient uptake that goes on in the midrow since roots are active there due to all the rainfall. Other dryer areas go into the growing season with pretty dry soils so the only area where you have to worry about competition is right under the emitters.
There seem to be a lot of growing pains in the first year of switching to no-till as you’re suddenly without the easy button to deliver a slug of nutrients to your vines. The benefits that no-till provides are soil structure and organic matter. These things take some time to form. You may need to fertilize more than you normally do. If you’re an organic producer, which you may be if you’re considering no-till, that’s going to be a significant expense if you suddenly have to give everything a shot of expensive organic nitrogen.
On the flipside, if you have an overly vigorous vineyard, no-till can do a good job soaking up some of that extra vigor.
Plants don’t just compete they actively sabotage by way of what’s called “allelopathy”. If you’ve ever wondered why your vines look like crap around an oak tree, that’s allelopathy. Vines don’t play well with others and some weeds and covercrops especially if they’re in the vine row have a similar action.
Another limitation is that there is no ideal covercrop. Ideally you have a nice low-lying covercrop that you can seed once. It reseeds itself. It doesn’t take over. It gets tall and you cut it and it shades out all other growth. In the case of grasses, you have to cut before they seed otherwise they’ll be too tall. Leguminous cover crops aren’t nearly as assertive, but they also don’t provide nearly as much organic matter or ground cover.
The big problem that a lot of growers face when going no-till is rodents. That nice mulch you create by mowing is the perfect place for gophers and ground squirrels to hide. If you have untilled vine rows, voles can be a problem. I’ve seen new vineyards (and some fairly mature ones) scrapped entirely because voles girdled the trunk of every vine.
Tilling also does a really good job of getting rid of burrow systems, which is important if you struggle with ground squirrels and gophers. The occasional till chops those guys up and doesn’t allow them to build a city under your vineyard. I’ve seen infestations of ground squirrels so bad you can’t even take a step without falling through the ground into a burrow. They will eat the roots right out from under your vine.
Definitely not the easy-button
All of this boils down to the fact that going no-till is going to be more expensive and more time-consuming than conventional farming. The growers I’ve spoken to who have gone no-till have a worker whose specific job is trapping rodents for at least two to three days a week all season long. That adds up to a lot.
Another thing to consider when going no-till is that you’ll probably need some specialized equipment. If you’re just doing the tractor row no-till, a mower may suffice plus a weed knife…assuming you are also getting rid of herbicide. There are a lot of fun toys out there that you can check out for undervine weed control. The finger weeder is an interesting one. It’s actually a passive implement that doesn’t require any power from the tractor to work. It just rotates with the forward movement of the tractor. The Multiclean is another minimal-disturbance implement. Our farming company has one of these and they seem to like it. Timing is really everything. If you let the brush get too high, you will have a tangled mess on your hands. It’s especially hard in vineyards with high-water holding capacity as you may not be able to enter the vineyard with a tractor before the weeds have already taken over.
You’ll need to rethink how you reseed your cover crop. You can’t just broadcast seed over an untilled surface and assume they’re going to take root. There are some direct seeders out there specifically for this reality but again, it’s an investment.
The limitations to undervine weeding or tilling, if you’re still planning on tilling the vinerow are topography and vine spacing. These implements are always harder to use on a steep and/or uneven incline. If you have tight vine spacing, the tool may not have time to fully rebound and swing back in between vines. That will leave a lot of missed spots.
One thing to keep in mind when transitioning to a reduced or no-till system is to adjust your expectations. Nothing looks cleaner than an herbicided vineyard. You’re going to have missed spots here and there and you’re going to have some weeds. Getting over the mental block is a big one for some people.
Find what works for you
Even if you aren’t going hard core no-till, there are ways to simply reduce tillage, which is still a step in the right direction. A lot of vineyards we work with till alternate rows and switch every 3 to 5 years. As I mentioned, wall to wall no-till under the vines is a whole lot harder, so maybe you just want to keep your midrow non-tilled and use a weed knife undervine. That’s still good.
If this is something you want to do, the best option is to design future blocks with no-till in mind. The above picture is from a ranch in Paicines managed by Kelly Mulville, who’s the viticulturist who thought this design up. He’s trained the vines on a high wire and the dripline is also really high. This allows him to run sheep all year long, which is great because normally you have kick your sheep out once your vines get tasty. The high dripline too is a really good idea. It makes a lot of undervine implements easier to use as a low dripline gets in the way. I know growers who have spent all winter raising the dripline wire 6 inches just so they can get a Multiclean to work.
There are some places where despite the benefits, we really don’t recommend no-till. Don’t plant a new vineyard on untilled soil. Your baby vines are not going to be able to handle the competition. Also ripping is the only way to break up any hardpans you have and incorporate any amendments that you’ve added.
Rodents can get out of hand and so can weeds. If you have an outbreak of star thistle or something else that is really aggressive or if you have an underground city of squirrels under your vines, just till. There’s no point in being a martyr.
The picture above is of a vineyard on Mount Etna in Sicily. The Etnean viticultural area is spectacular and it’s almost completely tilled, mostly because they have this one kind of wild chestnut that, if left alone for a season, will grow a tree right in the middle of your vineyard. Like Etna, there are some places where no-till just doesn’t work.
If this is something that interests you though. Go for it. Throw everything against the wall and see what sticks. Like everything, a one-size-fits-all mindset isn’t going to work. If you’ve been growing grapes for a while though, you already knew that.
Articles:
Chen, H., Dai, Z., Veach, A. M., Zheng, J., Xu, J., & Schadt, C. W. (2020). Global meta-analyses show that conservation tillage practices promote soil fungal and bacterial biomass. Agriculture, Ecosystems & Environment, 293, 106841.
Nunes, M. R., Karlen, D. L., Veum, K. S., Moorman, T. B., & Cambardella, C. A. (2020). Biological soil health indicators respond to tillage intensity: A US meta-analysis. Geoderma, 369, 114335.
Wolff, M. W., Alsina, M. M., Stockert, C. M., Khalsa, S. D. S., & Smart, D. R. (2018). Minimum tillage of a cover crop lowers net GWP and sequesters soil carbon in a California vineyard. Soil and Tillage Research, 175, 244-254.
