[Retrospective] Vineyards Special #1: The Wonders of Cover Crops

EPISODE SUMMARY

While we will continue to make new episodes, there are times when we feel the urge to highlight a past episode – because the topic it covers becomes news and the show shares some great insights, or because it is content that our newer listeners might have missed out on. Since last year was the International Year of Soils, we will be republishing a few of our best episodes about soil and soil health to get a fresh perspective in light of all the progress that has been made on the issue.

To round-off the series, we’re ending with a in-depth look at a popular and very effective sustainable agricultural technique: cover cropping. In episode 16 of our show, we had with us Bob Cannard and Bob Shaffer – both experienced sustainable farmers and horticulturalists. They shared their techniques with us, explained just how cover cropping works and how beneficial it can be, and gave us their expert advice. We learned a lot about cover crops in making this episode, and if you’re wondering after the last two episodes, just what exactly the sustainable agricultural techniques might look like that we need to start pushing for – this is the episode for you.

Links to other episodes in the Series:

Episode 1

Episode 2

Episode 3

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Photo by Robert Reed, courtesy of Recology.

Cover crops are becoming more and more popular, but they still aren’t completely understood by everyone. Bob Canard, can you tell me what exactly cover crops are, and how do they work?

Bob Cannard: Cover crops are nature’s way of preserving, enhancing and balancing the soil. All they are, are crops that grow naturally, or are planted, that are allowed to grow and establish and protect the soil, cycle nutrients and actually build soil, absorb atmospheric carbon, deposit it in the soil as food for the soil biology, which is the important digestive force of all life.

Bob Shaffer: Yes, cover crops are simply plants. Now, we’re going to chose the genus and species of plant that we call a cover crop, or, as Bob said very brilliantly, we can also just accept the resident vegetation – that which is growing in a field or pasture. But let’s recall that plants are the organism on earth that harvest carbon out of the air and puts that carbon into a form that we call organic matter. So plants are literally producing organic matter on earth that we then can introduce into the soil as a carbon source, which is food for microorganisms and other animals, and then also the plant above ground is protecting the soil surface.

Where are cover crops most popular?

BS: Cover crops are being used every place around the world right now, more and more every time. I’ve watched Napa and Soma Valleys (California), as I’m sure Bob has also, become quite well cover cropped compared to ten or fifteen years ago; they’re more and more used all the time every place.

Bob Cannard, as a long-time cover crop user, can you tell us the key benefits of using cover crops, as opposed to mulches and other methods?

BC: They stimulate the soil biology: all plants produce lots of sugars and other complex organic molecules that they pump into the soil and establish a relationship with the soil, so they actually nurture the soil. At the same time, their root system breaks up (subsurface soil compaction), and cycles nutrients from deeper profiles to the surface, making the soil more aerobic and balanced towards aerobic life – which it’s all about.

By comparison to mulching, they grow many cubic yards (depending on the intensity and the size of the cropping system) of compost for the soil. And mulching – you’re getting that organic material from another piece of ground, and it sacrificed its organic material to turn it into mulch or compost, which is spread on the ground, and it takes a lot of BTUs of petroleum energy in order to do all of that and spread it. Whereas the cover crop is very low energy input: the seeds are planted and they grow, and they harvest that atmospheric carbon, and deposit directly into the soil without those heavy inputs.

That’s a very interesting benefit.

BS: It’s very expensive to grow mulch on one piece of land, take the carbon from that land and move it over to another. We’d like to grow and use the cover crop as our source of mulch.

Bob Cannard, you manage hundreds of acres of vineyards that use cover crops successfully. Can you tell me a little about your strategy and what cover crops you use?

BC: We have a thousand acres in cover crops. Every winter time is the rainy season, and we plant in the fall after harvest, or just before harvest. We used mixed seeds and I’m a great proponent of a mixture of cover crop plants.

First off you need very low energy, quick germinating nurse plants that hold and protect the soil for the higher-level life support plants that come along slower and later. The cover crop protects the soil from all kinds of erosion, and the little quick growers do that quickly. They don’t provide too much organic matter, but they really help the next stage, and the next stage is perhaps the low proteinaceous broad-leaves, and then you’ll phase in to the higher proteinaceous grasses – more and more biomass. And finally, the high level of life, long term blooming plants, like the clovers and the vetches and the peas and the beans – the leguminous plants that take much longer to mature. Each one helps the next one, and the diversity is a very important element.

We like to grow our cover crops and let them stand to as full maturity as possible. In the organic kingdom, there’s lots of conversation about green manure cover crops; well, they break down very quickly and release lots of nitrogen. What I’m looking for is lots of carbon, and stimulating the free-living nitrogen-fixing biology of the soil, and this vastly reduces the need for nitrogenous influences, applications, fertilisers on the vineyards – and in the vegetable gardens as well.

Can you get a little more detailed about the process and tell us when you plant the seeds, how you cultivate it – if you do at all – when you mow it, and how you manage it all?

BC: Well, it depends entirely on the site. Some sites, hillside sites, are never cultivated and the cover crop leans progressively more towards perennial plants. Other sites are cultivated, but we do our best to cultivate as late as possible, allowing the cover crop plant to come to its maturity. When you try to incorporate a green plant, like a green manure, it has only lived a portion of its life and it has a high nitrogenous body; whereas if you allow to as great a degree of maturity as possible, it dries out, it makes its own seeds (some varieties reseed themselves and don’t need to be included in successive plantings), and it’s straw is carbonaceous and has a longer than one year half-life in a temperate climate. So you actually build soil carbon, the foundation of the soil digestion, which is an absolutely critical motion. Everything has to have good digestion, and that digestive force solubilises the minerals. Additionally, on the soil surface, that straw spawns and sponsors the various yeasts, so we are less dependant upon yeasting the pressed grape juice to make wine, and we can use the indigenous yeast of the particular site in many cases which means we get the true terroir, or taste of that soil and that location.

To be clear about the general process of cover cropping: you plant the seeds, either in spring for summer cover crops, or in the autumn for winter cover crops. You can use it as a green manure by mowing it and incorporating it into the soil when usually when it’s flowering and still green, or you can wait until it’s a little woody and chop or mow it down to use as mulch. Is that correct?

BC: Yes, it’s mowed down or grazed down, and maybe cultivated, or maybe just mowed and grazed – it depends upon the plot and the variety, and air drainage, and many, many variables. We’re always trialling little plots of little pounds of sprinkling here and there, and it takes a while to grow the soil; if you have a herbicided, clean cultivated, long-standing degraded soil, high level of life plants like clovers may not take hold, because it doesn’t have properly developed soil biology yet. But through the use of incorporating the maturity of the cover crops over seasons, the soil population will change and you’ll get the nice, soft, beautiful, proteinaceous, easy to work with kinds of plants, and they will take over from the thistly, thorny, creepy-crawly, difficult types of plants to manage.

So viticulturalists should be prepared to invest a bit of time at the beginning if the soil isn’t healthy already. And is there anything specific to vineyards that viticulturalists need to understand about cover cropping – is it much different to cover cropping for farms?

BC: Not particularly, but the height of the type of plant and whether it’s an annual cropping cycle or a perennial, and its degree of maturity so that it can become reseeded, so you don’t have to reseed it annually – at least not with all of the species…

We use early season grazing of sheep and goats at high density, quick rotation so that they aren’t over-grazed but just appropriately grazed. The sheep actually stimulate the regrowth of the cropping system, so it responds as the season advances into the summer time with a good early maturity. Then, in many cases where it’s just mowed, what you end up with is all of this reflective strawy grass on the soil surface – not just grass but all the plants that turns golden as it dries out – and it reflects heat back up to the fruits underneath the canopy and actually increases the warmth and the dryness of the canopy. This reduces the incidents of mildew, and stimulating this broad array of canopy biology that additionally enhances the resistance of the plant through species competition of one dominant mildew type problem.

That’s a unique benefit of cover cropping, or mulching. And Bob Shaffer, do you want to add anything? 

BS: We have to recall that viticulture is a monoculture, often times at least, and I see the cover crop as a way to bring diversity, and to break the problems that are associated with monocultures. Also, I can rotate the genus and species that I use; I can rotate them over space, I can rotate them over time, so it actually adds, not only diversity to the monoculture, but adds the component of rotation. For example, I can put perennials on one side of the vines or tractor rows; I can manage that as a perennial cover for a few years, and then I can have annuals on the other side. I can also use those annuals and/or the perennials – or specific strips planted through the vineyard – as a beneficial habitat and food sources for beneficial insects, beneficial life forms in the vineyard. So, in all ways, the cover crop – if selected and managed well – can be the source of diversity, can be the source of rotation, and the source of beneficial life forms brought to the vineyard.

There are many variables when it comes to cover cropping, and there is no “one-size-fits-all” approach, but is there something you would recommend to everyone starting off with cover cropping?  

BS: It’s something that teaches you. I’d encourage people to immediately start cover cropping, and all farmers must always have trials going on. These do not have to be large, expensive, exhausting procedures, but having some type of trial always going on in the farm shows you where to head next. It also is your little classroom where you can go out and look and learn. So having at least some strips of cover crops – of different species always – to learn what to plant next is a good idea.

There are a lot of species to choose from as well. Bob Shaffer, what are your thoughts on choosing the best species for vineyards?

BS: On choosing species, one of the things you want to do, as Bob Cannard pointed out, you want to use a polyculture. I’m always going to use a mix of grasses, legumes and forbes when I’m planting. Also, as we broadcast it or drill this type of mix, the site itself will sort out which plants are most appropriate there.

In frost-prone vineyards, cover crops may the increase in risk of frost damage. What is your advice regarding this?

BS: Certainly if I’m going to put a cover crop into a frost prone vineyard, then I’m going to add the important component to the cover crop that we haven’t directly mentioned yet, which is as important as species selection, or any other feature of the cover crop: the management of the cover crop. So, if I have frost concerns, I’m going to select cover crops that are low growing, and then I can manage the cover crop in the frost season by further mowing it – at least on one side of the rows to allow some air drainage. Also, if you’re using broad-leafed species, they tend to have less of the ice nucleating bacteria on their leaf surface, and are less prone to causing frost problems in the vineyard or orchard.

I want to address another common worry that people have regarding cover crops, which is water usage. Wouldn’t cover cropping add extra irrigation costs for drier climates?

BC: We grow over-winter cover crops and we utilise rainfall as a natural irrigation, and it actually increases rainfall infiltration by reducing soil compaction. So actually, we reduce irrigation requirements; and then, it’s depositing on the soil surface at maturity, high levels of carbon, and one unit of carbon will support and hold approximately eight units of water. So, we increase our water holding and infiltration characteristics by increasing the organic matter content and the root zone development through cover cropping.

Yes, I read in a couple of articles, including a 1994 research article in the California Agriculture journal, that winter crops generally have very little impact on soil moisture compared to summer cover crops – so that would be a good option for vineyards. And Bob Shaffer, do you have anything to say about water usage or to add to Bob Cannard’s point?

BS: The cover crop, particularly because of its roots being in the ground, increases the humus levels. As those roots decompose, it increases the humus level, and this is the material that Bob Cannard was referring to as holding more water in the soil.

Though I will say that, sometimes if I have an existing vineyard, maybe it’s old and maybe the soil is weak and worn out, the transition period of introducing cover crops into that vineyard – there has to be some care taken to make sure that we don’t take water away from vines. Obviously, a cover crop plant uses some water when it grows, but it’s more an issue of timing: both timing in terms of transitioning into a cover crop (where the vine gets used to having other roots around it) and also as we build humus in the soil, there’s a little transition time that’s needed for that. And then, if we use a little water in the spring time for the cover crop, that doesn’t take away critically from the other crop – whether it be vines or some other plant; but later in the year, as the cover crop has been managed into a mulch, we’re actually using less water because we’re protecting the soil surface, we’ve built humus in the soil… And so, the timing issue on water needs to always be addressed rather than saying “okay, does the cover crop use water or not”.

So the takeaway from this is that timing is everything and it may increase water usage at the beginning, but in the long run it will actually save water. And now onto the management question: I presume it takes a little more time and effort to manage cover crops – wouldn’t this increase management costs?

BS: Considering whether cover crops raise our management costs, we have to look at the whole farm, and look at the multiple benefits that the cover crop has brought to the farm to address whether we lost or benefitted in terms of management dollars.

Can you both give me some examples?

BC: Well, my field, these vineyards that I assist in managing were conventionally grown and heavily cultivated, and herbicided underneath the vine rows. And we had, when I first took over twelve years ago, a preponderance of tenacious, noxious weeds that interfered with the canopy of the grape vine, and through management of the cover crops – planting selected varieties and improving the soil, and utilising inter-crop grazing of the sheep and the goats – after twelve years now we have very few noxious weeds and it’s actually reduced our over all costs; weeds that would shoot up from the herbicided strip into the canopy that had to be mowed or supressed in one fashion or another.

BS: Another aspect of management that cover crops can safe you money instead of cost you money would be for dust control, for example. A lot of times a vineyard or farm will get very dusty during the dry season, whereas if we have cover crops and we’ve managed over to stubble and/or mulch on the surface, it reduces dust. That dust can increase mite pressure in the vineyard, so if we have mulch and we’re absent of the dust, then it decreases our cost of spraying for mites, or managing for mites. There a number of other features that we could name that the cover crops actually decreases management costs.

One of the benefits I came across was the introduction of beneficial predator insects that keeps pests down. Has that been your experience?

BC: We’ve had very few problems with pests.

BS: Certainly, if you provide habitat and food for everyone, then the system tends to become more balanced. Where there are appropriate numbers of predators, there are appropriate numbers of prey. As the goal in “managing the farm” or “managing pests” is not to eliminate all the pests; it’s simply to increase the antagonism from the pest’s predators. And we do this by carbon, we do this by having flowering plants; nectar, pollen, habitat, and carbon above ground.

If anything, I’ll say the cover crop, with all the glory that we’ve talked about and the beauty of the cover crop, still: the cover crop shouldn’t be viewed as all we need; we always have to look after the whole system and say “okay, look: I’m going to manage organic matter, which includes cover crops, compost and mulches. I’m going to manage minerals. And I’m going to manage my tillage”. Those three areas: OM management, mineral management, and tillage management all need to be considered, all need to be cared for to have the cover crop show its best; to have the compost to show it’s best, and to have the minerals show its best. They’re linked in biology, they’re linked in being foods, and they’re all necessary to manage at the same time to get the best benefits.

So a holistic approach is really what you’re going for. And are there any other benefits to using cover crops that would outweigh other management costs?

BC: The cover crop and the soil surface organic material holds and supports the soil, where many clean, cultivated and just bare soil surfaces can be very tacky. Let’s say during harvest we have modest rainfall, then it impedes the ability for the harvest crews and the equipment to move through the vineyard because of the muddiness, whereas with the increase of soil surface organic material (and especially the dry carbonaceous material), the soil surface is held and supported by the residual root systems. And the soil surface itself is protected by the strawy organic material, and this really reduces the stickiness in many different ways: just physically at a large-scale straw level, and at a digested carbon level/humus level it allows the soil particulate matter to be happy with itself and want to stick to other elements, such as harvesters feet

That’s an interesting benefit that I wouldn’t have thought of, actually.

BS: That’s actually a huge benefit, even during the year sometimes with the irrigation systems, if you have cover crops it enables workers to have less mud on them, and to have some place to sit down; to have some place that’s green and flowering instead of just a bare herbicided soil. There’s a huge difference in the vineyard for both the people and the crop when we use cover crops.

We’ve covered a lot of ground in this episode already, although we could probably go on forever. But for the final question: are there any issues you want to address with cover crops, or anything else that viticulturalists need to keep in mind when cover cropping?

BC: Well, it’s a possibility that you might have overgrowth. A lot of viticulturalists, back to frost issues, are worried about canopy heights of cover crops. Well, there’s legitimacy to this, because it reduces air drainage, but at the same time, a high-density cover crop of good, bread-leafed plants has a better canopy biology to it that resists frosting. And those plants are also respiring energy and actually warm the vineyard’s atmosphere on cold nights.

No, there are definitely problems, and it’s a progressive activity. A novice viticulturalist beginning to grow cover crops might be afraid to let them come to maturity, and boy, that’s all right – it’s a beginning. And as we develop and grow, we develop more confidence as we grow, and we also develop our soils and select a broader diversity of cropping specimens, a variety, and allow them to come to greater maturity.

BS: That’s certainly experience speaking, and I’ll say to summarise that excellent comment by Bob Cannard: I would encourage people to view cover cropping as a transition, as part of a transition into more healthy soils, and to better above-ground relationships, rather than an instant change.

Well put. So, cover cropping is definitely beneficial, it just takes a little bit of time and a little bit of effort to get it all going. But once you have the experience, it’s probably the best way to go. Unfortunately that’s all we have time for I’m afraid, thank you Bob Cannard and Bob Shaffer for coming on the show.

BC: Well, thank you for your interest.

Vineyard Special #2: Using Composted Mulch For True Cost Benefits

In this second part of the two-part special on vineyards, we speak with CEO and vineyard manager of Food and Beverages Australia Limited (FABAL), Ashley Keegan about the costs, risks and benefits of using composted green organic mulch on vineyards. We go into detail about sourcing a good quality product, cost-effective strategies for applying the mulch, the incredible increase in yield they experienced, as well as the water saving capacity of the mulch, and much more.

Thank you to YLAD Living Soils for making this episode possible.

YLAD Living Soils is an Australian owned company formed to supply sustainable biological, organic and humus compost fertility products and programs that support the natural balance of the physical, chemical and biological aspects of the soil, lessening the reliance on conventional chemical fertilser inputs. Find more on their website.

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Ashley, you’re the CEO of FABAL (Food and Beverage Australia Limited), and FABAL is a commercial farming company that manages agricultural businesses across Australia. Can you tell me more about FABAL?

Ashley Keegan: We’re a large agribusiness management company based in Adelaide, South Australia. We operate a number of viticultural enterprises, but also other horticultural operations as well. It’s pretty much spread across the country, with a focus on viticulture in South Australia.

You manage agribusinesses. Do you manage them solely for clients or do you own some yourself?

AK: We own our own, and also manage for others. So, if you’re a company that owns an asset, or you might be an individual, but we also do that work as well. But, we ultimately own a large percentage of what we do ourselves. We also do some consulting work for the industry on an external basis as well.

How many hectares of vineyards do you manage at the moment?

AK: We have about sixteen hundred hectares under management at the moment.

Sixteen hundred hectares is nearly 4 thousand acres, so that’s quite a lot. What are your key performance indicators; what do you take into account when you’re managing and improving the vineyards?

AK: Interesting question. I’m an agronomist by training, and a viticulturalist, but my managers call me the accountant now, because we have to measure the bottom lines of anything that we do. And again, I guess I look at it a bit more broadly in terms of return on investment, whether it be purely from a financial point of view, or a return on investment of our time, or our technology – any of the inputs that we put into our operations. We do extensive internal and external benchmarking from a KPI perspective, but my philosophy is to try and be in the top five percent in anything that we do. Again, when you start to benchmark yourself across the sector, ultimately you go to financial metrics pretty quickly to be able to do that in an objective manner.

Financial success is of course important to you, but in terms of return on investment you take a broader view and include things like labour, time and technology. Our topic today is the costs, risks and benefits of using composted mulch on vineyards. Can you tell me what exactly you use on your vineyards?

AK: Effectively, we’ve done several different trial works with a lot of different products. The products that we’ve mainly settled on now are the composted green organic mulches. So it’s a green organic waste composted through the Australian Standard 4454. We can have them specifically to different aggregate sizes, and different fines profiles, depending on what we’re trying to do with the product.

Where do you source the product?

AK: Our compost comes from commercial compost suppliers, and in our city there’s two or three main suppliers that do that. The majority of the material that we use comes from a feedstock that is kerbside collected. So, I’m not sure of what happens in other countries, but in Australia you have a two hundred and forty litre green wheelie bin that the home gardener can put their lawn clippings in, their pruning in, and in some circumstances can also put food stuff into the stream. Those bins are collected, taking it off to a processing facility, where they’re composted. That process then will generally do a few things: create a blend and a particle size profile that is what I’ve ordered up. So, that’s where we get our product from.

Regarding the specifications you ask for – do you make specifications for each particular site, or is there just a general blend that you use for all vineyards?

AK: That’s a really good question, and it’s not specifically with our site. I do fiddle with the specifications when I’m trying to ask the product to do something a bit different. If I’m looking for more of a mulch versus a soil conditioner or a fertiliser, I will manipulate the percentage of fines in the product. If I’m looking for a more mulch, water-saving product, then there’s a coarser fragment in there. If I’m looking for, sort of a multi-vitamin for my vines, then I tend to get a blend with a high fraction of fines in it that break down very rapidly and give the vines almost a hit that’s equivalent to green organic fertiliser hit.

Can you give a bit of context to the operation: when did you start using composted mulch, and why?

AK: We started, I’d say, doing that in a substantial way back in 2003, and 2003 in Australia was the start of quite a dry period that spanned over seven years, particularly in the south-eastern areas of South Australia. We went into, you know, on our history it’s recorded as a one-in-one-thousand year drought. So, rather than necessarily just hurl more water at a vineyard, we started looking at the options for investing in some composted green organic mulch, and doing some trial work with that.

We were pretty fortunate that there’d been a fair bit of work done in Australia – Katie Webster, John Buckerfield had done a fair bit of work with the products that we had available to us, so that there was some good, objective, empirical data for us to make some of the decisions that we had to make at a practical, commercial level. So, we weren’t having to start at a zero-base there. I was able to make some of those decisions – reasonably big decisions – and in 2003 we undertook a significant exercise in mulch: over six hundred hectares of vineyard in one year, and thirty-three thousand cubic metres of composted green organic mulch. Probably one of the largest single exercises ever undertaken in the country. We dove in the deep end!

For our audience, that study is the CSIRO Report “Compost as Mulch for Vineyards” by John Buckerfield and Katie Webster, which found that in certain circumstances, using composted mulch can increase yield by up to 35% and mid-summer soil moisture by 30%. But even still with the research, there were of course costs and risks involved in starting a new practice in the vineyards. Can you maybe explain those a little bit? I’m sure you were very cautious even still?

AK: Yeah, we were, certainly, and from a point of view…we mitigated the risks, for want of a better term, based on research. There are a few risks associated with it from the point of view of the type of application, the density, the application ratio – you need to be a bit careful with that. The research was pretty strong on water saving, and that helped facilitate a commercial payback. At the same time, it was pretty simple to do a nutrient analysis of the product, calculate that into our normal fertiliser programmes, and take that out of the three-year breakdown period, and do some economic benefit of that. So, yeah there was a risk, but what I’d call the agri-risks of that were pretty low, pretty controllable from our perspective.

Apart from risks, there are definitely substantial costs with starting to use composted mulch – can you tell me what the costs were?

AK: Because of the volume that we embarked on that project, we had a purpose built spreader made to be able to spread that particular product, and that was a reasonable investment, but in the context of the overall spend it made sense for us to do that rather than use a contractor. But, the costs involved were commercial at the time, and it was relevant to the market at the time; the market was pretty buoyant, we were getting paid reasonable prices for our product, and the economics stacked up. But just to put it in context for you: the compost itself was around about, just in rough terminology – but around about two-thousand dollars a hectare in material, but it cost you around four-hundred and fifty to five-hundred dollars to actually apply it to the paddock. So you’re looking at around about a two-and-a-half thousand dollar expenditure.

And that’s in Australian dollars, which would be roughly 2300 US dollars, and 1700 euro.

AK: Yeah. And just to put some context around that’s in the background spend of about six-and-a-half thousand dollars per hectare of normal operating expense. So in a single year we loaded thirty percent on top of our annual operating expense to do the exercise; but again, the research was showing that you would get three years worth of benefit out of it – and again, like all good accountants, you just spread that over that period as well.

So in one year you added 30% extra to your annual operating expenses to do it, but like you said the research showed that it lasts 3 years, so spread over three years, it adds just 10% to the operating expenses annually. Those costs were predicted costs, but were there any costs, or risks, that popped up during the operations that you hadn’t accounted for?

AK: Yeah, I’ve spoken about our experience on a number of occasions in our industry level, but I had one of those crucible moments when I was interstate on one of our other properties and I received a phone call from one of the managers from one of the sites that were spraying this material to inform me they’d identified some contaminants in the product. And this kerbside collected material does have some contaminant background in it, whether it be glass or stone, or anything that goes into your green wheelie bin.

But imagine our surprise when we started identifying syringes in the product; and that ground our operation to a hold, as we had to embark on a whole series of risk assessments. And our understanding as to what happened with that is, a long story short, and a lot of effort short, was that obviously the food stream had been contaminated at some point in time with syringe containers, and had been through the composting process. And we ended up – on our six hundred hectares – having to rake the entire area, and after going through that process we identified over four hundred new syringes in the material that had to be extracted out of that material.

So, it’s probably a bit unusual that you see me sitting here still being a card-carrying supporter of compost after grinding our business to a halt and creating an amazing logistics and practical [impact] on our business that we still deal with today. But what we had to do was understand very clearly that those contaminants represented a negligible risk that we had to put in procedures to manage around that – including identifying those risks to visitors to our properties, and our customers. So, we got together as a business and we looked at those risks and fundamentally we decided as a group that the benefits we were targeting and the support that we had for the product still mandated that we were comfortable to move forward with that.

We worked with the industry pretty hard to make sure that didn’t happen to any other group, and the industry responded pretty well. But I think coming out of the back of that, and the message that I recount to people, looking at that kerbside collected feedstock, is that you need to be careful about the fact that…really, the syringes were acute and emotive, but what they represented to me was just risk, and that if syringes can find themselves in your feedstock stream, then there are probably no rules about that, and as a community – as a supply chain – we really need to work hard on making sure that the public who are putting material into their green wheelie bins, understand the implications and the ramifications of the decisions that they make on their front lawn.

Yes, and we’ve spoken a lot about education in the past, and the importance of connecting people with the process so that they understand where their organic materials go and what happens with them. For example, when speaking with Gerry Gillespie of City to Soil, he told us about their extremely low contamination rates, and he attributes that simply to making people understand what happens with their organic materials.

We go into detail about this in Lesson 4 of our online course on Compostory.org, and we go through the whole process of how to set up an education and communications strategy when you’re implementing a new kerbside system – so anyone who is interested can check that out.

But as a business like yourself, what can you do to help control the contamination rate?

AK: I think that if I was talking to – well I guess we are potentially talking to people considering using it – you really need to do your homework with your suppliers, you need to do the homework on the product. And I’m not sure of the standards in other countries, but there’s an Australian standard for composted green organic, and it’s a basic standard but it’s a good Australian, or international, standard as to what actual process it has to go through. That’s a really good first start. It’s not everything, and frankly it’s the base hurdle that the product should jump over, and that helps manage some of the agri-risks, but it also demonstrates that this is actually operating in a sustainable, professional manner.

And then you really need to go around and get your hands dirty and have a look at the product, look at the process; and understand that if you’re just buying a couple of bags, it’s a return on your time, really, but if you’re looking at embedding it into your production systems, then it’s imperative that you go and have a look at not only the process, but I’d argue [you need to] understand very clearly where the supply is coming from. And ten or eleven years down the track, we’re quite discerning about feedstocks going into our composted green organic mulches. We still use kerbside materials, but we also use very specific streams, and we also have a supply base that will create blends from specific streams for me as well.

My experience with the industry is that it’s pretty proactive in that context. Every day the technology improves for sifting and sorting and managing contamination in the kerbside products, but nothing beats stopping it getting in there. And I think that as a community, as an industry, there’s still a lot of work to be done to make the home gardener understand the sheer responsibility that they have. Because it dramatically adds to the cost; it dramatically impacts on the decision-making of blokes like me, and if we could remove those variables – if we had a magic wand that could remove those variables, then look out, because the product is a very powerful product.

Going back a bit, contamination was the biggest risk you encountered, but for costs – what were the biggest costs that you experienced, perhaps transportation of the product was the biggest cost?

AK: Definitely the distance to the producer is really important. It doesn’t weigh a lot, so the bulk density of the product generally, you know, you can only jam so much in a truck. So, there’s a large volume for weight that you’re transporting. So, I guess this is where some of the other products have gone to [muffled] structure and try to get a bulk density increase, but unfortunately you lose some of the benefit of that loose, open-aired structure that you’re looking for with the mulch.

So, certainly transport is a big factor. It’s probably dangerous for me to talk about percentages of that, because it’s so variable depending upon how far you are from… But it can range from ten percent of the product cost, to forty percent of the product cost.

Let’s talk about the strategy for using the composted green organic mulch on your vineyards: I know you’re keen to get the best value out of the product, so how do you apply the composted mulch to achieve this?

AK: We started with a very blanket approach, non sophisticated; start at one corner of the paddock and go to the other corner, and that was as sophisticated as our strategy got, because we were looking for that water-saving, fertiliser input benefit across the whole board. Then we found, almost by accident – we use remote sensor satellite imagery on our vineyards to look at biomass – and what we found by accident when looking at some of those images – after we’d done the mulching work where we’d put in some trial works – was we were having some profound impacts where we were taking low biomass, low vigour areas and really dramatically shifting those profiles.

And it got us thinking about how we can maximise the benefit of that, and it dovetailed into the fact that, as the product is reasonably expensive, you want to put it where it’s going to give you maximum value. And we started to do some trial work on that, where we looked at taking it into the weaker sections of our paddocks, applying it to those, and then looking for a response out of that. So, just to give you a bit of a background as to that in viticulture especially: vineyards are very linear. They’re built on trellises and they’re very linear, and no matter how accurate you were with your source surveys and your selection of the paddock, you end up having high vigour areas, or stronger areas, and some weaker patches on shallower soils.

And managing that vigour variance…that’s viticulture 101. And we do that generically be managing our fertiliser and trying to trim, or managing our irrigation as best as we can, but you end up trying to average that out against the whole block. And what we started to do was some experimental work where we just went into the weak sections and apply it, and then task the satellite again to have it look at another image to see if we could even out the vigour. It was really quite astounding, the responses that we were having on that – and I guess that satellite imagery allowed us to objectively validate that as well.

At this point you started to look at the cost benefit of the mulch – so what were your findings?

AK: What we found was, if I explain to you: you might have a ten hectare paddock that might be contracted to a certain customer and they might say you can deliver a hundred tonnes off that block. If that block is delivering you a hundred tonne, that’s great and everybody’s happy. But in reality, what happens in most paddocks is that half that paddock might be delivering you twelve tonne to the hectare, and the other half of the paddock might be giving you eight tonne to the hectare. That’s really crude, but you’ve got sections that are weak and harder than other sections. And if at the end of the day the equation equals what your customer wants, then everybody’s happy.

But if you’ve got a situation where you’re under performing because the vineyard is not delivering to its capacity, intrinsically what you try to do to meet that contractual opportunity is you try to drive the vineyard a bit harder. And that exacerbates this variability, if you’ve got a problem, it sort of becomes a spiralling cycle at that point. One of the great things we found with the mulch was – when we started to put GPS sensors on our harvesters, and we tracked and found this new variation that was happening in our paddocks, and we lined them up with our biomass images from the satellite’s on the canopy densities – that the correlations were pretty good.

So, we figured that if we can make the weaker sections of our paddocks work a bit harder, then we don’t have to drive the whole paddock up just to meet those obligations and meet those opportunities. And that’s where we really started to look at good, positive returns on investment. We did some work that we published a bit of, that showed the capacity to take areas, increase those in yield by twenty percent, or thereabouts. And depending on your price profiles – at that particular time it was a single year payback for us with a three-year delivery of that result. So, besides the commercial repo, it actually improved our product. It created a more even vineyard block, so our customers are happy; we’re happy because we’re meeting the targets, and we’ve actually minimised our requirement to spend money on the mulch as well. So we’re just putting it where we’re getting maximum return on it.

You experienced a single-year payback with a three-year result, that’s really excellent, though I suppose that’s particular to your experience?

AK: Yeah, the key point that I’d like to make, or I think is really important, is if I was to run that metric again today in a different price metric, different yield parameters…you have to be very careful, it’s going to be very specific to your site and the market you’re playing with. If you’re growing a very high quality product and where a tonne to the hectare makes a big difference because of the price point, then it amplifies the impacts. If you’re in a different quality spectrum then…you need to do the numbers yourself on that. But really, the key return on investment is if you’ve got latent potential, or under performing potential, and you can capitalise on that by returning that area to a better performing area. And therefore there’s a market for that fruit, there’s an opportunity to sell it at a certain price point.

The thing that jumps out to me is the 20% increase in yield. How was the quality of the grapes themselves? Because more does not mean better quality, necessarily.

AK: This is the other point: you’ve got to be really careful with that, because if you’ve got a vine that’s operating at a certain potential and you just make more vigorous to grow more tonnes, well there’s a threshold in viticulture where that could potentially detract from the quality of the grape. And that, again, to me is the advantage of targeting the weak areas that are under performing, and potentially haven’t got enough leaf over the top and have maybe too-exposed fruit: you can create a situation where you can grow a more healthy canopy on that vine and get better protection for the fruit, and at the very least, improve the quality of those under performing areas.

You mentioned water saving benefits and we talked about the study – but how much water did you save then in the end?

AK: We went into the whole exercise with a view that we were potentially going to save thirty percent of our water, but it was a particularly dry year – again, we were heading into the drought – so we almost abandoned the need for that. We almost ignored the water saving component of it; we wanted to maintain the biomass. So what we found was our ability, with the mulch on-board, to create a more healthy canopy than we otherwise would have at the same water level. The research that Katie Webster and John Buckingfield did – that’s really quite categorical in that they were looking at around a thirty percent water saving. And I’ve no concerns about that, that in the right applications you can deliver that. We personally now use the products in more of a remedial sense, and spatially remedially. So our whole aim is to take a block and be able to just apply a normal water level, rather than have to apply more water to compensate for the weak area of the block. So, we can fix the weak area and then just water the entire area normally.

Is there anything else that viticulturalists need to keep in mind in order to achieve success using composted mulch?

AK: I’m a huge fan, absolutely huge fan, of trialling everything. It costs virtually nothing to go and put mulch on a few rows and see what happens. And just record it; put a control in place, put a treatment in place, do that in three different varieties in three different soil types, and you’ll learn for yourself. And that’s ultimately how we started and ultimately what gave us the confidence to go really broad-acre on some of this strategy. But it started with two rows of vines and…You know, wiggle a finger and stick it in the air and see what happens! You know, there’s a bit more science behind it, because you can measure it and do the analytics that you need to do, but….

At the same time, I’d say it’s not for every site. If you’re on a high-vigour site or a wet site, you need to be very, very cautious about it, and you’d need to really have a look and a hard think about the applications for that. And my overriding comment with these products is just to know the source and know the quality of the product. And don’t be afraid to ask; don’t be afraid to have the analysis done, and look at the analysis and make sure you’ve done a little bit of background work on them.

I have one more question before we go. I wonder if you’ve ever considered using cover crops on your vineyards?

AK: It’s interesting, we did, and we compared cover crops. We looked at the biomass that we can generate with a cover crop, and the reality is we just can’t grow, internally, enough cover crop to make a material difference. A really interesting thing we did with cover crops on one of our properties was – almost using the same theory that we did with the satellite images – we’d grow cover crops in all of the vineyard block, and we use a forage harvester (which is a machine that cuts and collects the cover crop) to take it out of the paddock and compost it, and then bring it back in and spread it on the weaker parts of the block again. So, we’re actually using a cover crop to potentially de-vigour the high vigour areas, and at the same time taking the nutrients from there and transplanting them – with the compost process in between. We found that to be a really good way to draw down on a high vigour area by planting a hungry cover crop, and yet put that benefit back into the same paddock where it helps you even it out.

Fascinating, a really interesting way to use cover crops to control the vigour of the vineyard. And unfortunately Ashley, that’s all we have time for. Thanks for coming on the show today.

AK: Thanks!

Vineyards Special #1: The Wonders of Cover Crops

Episode sixteen is part one of a two-part series on the use and benefits of sustainable agricultural practices in vineyards. In this episode, we’re focusing on the use and benefits of cover crops for vineyards. With us to talk about this are agronomist and soil culture expert Bob Shaffer from Hawaii, and Bob Cannard of Green String Farms, who manages 1000 acres of vineyards for Cline Cellars in California. We’ll cover successful management strategies, choice of cover crops, pitfalls you may encounter, the unique benefits of cover cropping on vineyards and much more.

Thank you to Recology for making this episode possible.

Recology is an employee-owned company operating in California, Nevada, Oregon and Washington coordinating dozens of recycling programs to recover a variety of materials. In San Francisco, they are part of the program Zero Waste by 2020 and are very involved with compost production and distribution. Visit their website here.

Photo by Robert Reed, courtesy of Recology.

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Cover crops are becoming more and more popular, but they still aren’t completely understood by everyone. Bob Canard, can you tell me what exactly cover crops are, and how do they work?

Bob Cannard: Cover crops are nature’s way of preserving, enhancing and balancing the soil. All they are, are crops that grow naturally, or are planted, that are allowed to grow and establish and protect the soil, cycle nutrients and actually build soil, absorb atmospheric carbon, deposit it in the soil as food for the soil biology, which is the important digestive force of all life.

Bob Shaffer: Yes, cover crops are simply plants. Now, we’re going to chose the genus and species of plant that we call a cover crop, or, as Bob said very brilliantly, we can also just accept the resident vegetation – that which is growing in a field or pasture. But let’s recall that plants are the organism on earth that harvest carbon out of the air and puts that carbon into a form that we call organic matter. So plants are literally producing organic matter on earth that we then can introduce into the soil as a carbon source, which is food for microorganisms and other animals, and then also the plant above ground is protecting the soil surface.

Where are cover crops most popular?

BS: Cover crops are being used every place around the world right now, more and more every time. I’ve watched Napa and Soma Valleys (California), as I’m sure Bob has also, become quite well cover cropped compared to ten or fifteen years ago; they’re more and more used all the time every place.

Bob Cannard, as a long-time cover crop user, can you tell us the key benefits of using cover crops, as opposed to mulches and other methods?

BC: They stimulate the soil biology: all plants produce lots of sugars and other complex organic molecules that they pump into the soil and establish a relationship with the soil, so they actually nurture the soil. At the same time, their root system breaks up (subsurface soil compaction), and cycles nutrients from deeper profiles to the surface, making the soil more aerobic and balanced towards aerobic life – which it’s all about.

By comparison to mulching, they grow many cubic yards (depending on the intensity and the size of the cropping system) of compost for the soil. And mulching – you’re getting that organic material from another piece of ground, and it sacrificed its organic material to turn it into mulch or compost, which is spread on the ground, and it takes a lot of BTUs of petroleum energy in order to do all of that and spread it. Whereas the cover crop is very low energy input: the seeds are planted and they grow, and they harvest that atmospheric carbon, and deposit directly into the soil without those heavy inputs.

That’s a very interesting benefit.

BS: It’s very expensive to grow mulch on one piece of land, take the carbon from that land and move it over to another. We’d like to grow and use the cover crop as our source of mulch.

Bob Cannard, you manage hundreds of acres of vineyards that use cover crops successfully. Can you tell me a little about your strategy and what cover crops you use?

BC: We have a thousand acres in cover crops. Every winter time is the rainy season, and we plant in the fall after harvest, or just before harvest. We used mixed seeds and I’m a great proponent of a mixture of cover crop plants.

First off you need very low energy, quick germinating nurse plants that hold and protect the soil for the higher-level life support plants that come along slower and later. The cover crop protects the soil from all kinds of erosion, and the little quick growers do that quickly. They don’t provide too much organic matter, but they really help the next stage, and the next stage is perhaps the low proteinaceous broad-leaves, and then you’ll phase in to the higher proteinaceous grasses – more and more biomass. And finally, the high level of life, long term blooming plants, like the clovers and the vetches and the peas and the beans – the leguminous plants that take much longer to mature. Each one helps the next one, and the diversity is a very important element.

We like to grow our cover crops and let them stand to as full maturity as possible. In the organic kingdom, there’s lots of conversation about green manure cover crops; well, they break down very quickly and release lots of nitrogen. What I’m looking for is lots of carbon, and stimulating the free-living nitrogen-fixing biology of the soil, and this vastly reduces the need for nitrogenous influences, applications, fertilisers on the vineyards – and in the vegetable gardens as well.

Can you get a little more detailed about the process and tell us when you plant the seeds, how you cultivate it – if you do at all – when you mow it, and how you manage it all?

BC: Well, it depends entirely on the site. Some sites, hillside sites, are never cultivated and the cover crop leans progressively more towards perennial plants. Other sites are cultivated, but we do our best to cultivate as late as possible, allowing the cover crop plant to come to its maturity. When you try to incorporate a green plant, like a green manure, it has only lived a portion of its life and it has a high nitrogenous body; whereas if you allow to as great a degree of maturity as possible, it dries out, it makes its own seeds (some varieties reseed themselves and don’t need to be included in successive plantings), and it’s straw is carbonaceous and has a longer than one year half-life in a temperate climate. So you actually build soil carbon, the foundation of the soil digestion, which is an absolutely critical motion. Everything has to have good digestion, and that digestive force solubilises the minerals. Additionally, on the soil surface, that straw spawns and sponsors the various yeasts, so we are less dependant upon yeasting the pressed grape juice to make wine, and we can use the indigenous yeast of the particular site in many cases which means we get the true terroir, or taste of that soil and that location.

To be clear about the general process of cover cropping: you plant the seeds, either in spring for summer cover crops, or in the autumn for winter cover crops. You can use it as a green manure by mowing it and incorporating it into the soil when usually when it’s flowering and still green, or you can wait until it’s a little woody and chop or mow it down to use as mulch. Is that correct?

BC: Yes, it’s mowed down or grazed down, and maybe cultivated, or maybe just mowed and grazed – it depends upon the plot and the variety, and air drainage, and many, many variables. We’re always trialling little plots of little pounds of sprinkling here and there, and it takes a while to grow the soil; if you have a herbicided, clean cultivated, long-standing degraded soil, high level of life plants like clovers may not take hold, because it doesn’t have properly developed soil biology yet. But through the use of incorporating the maturity of the cover crops over seasons, the soil population will change and you’ll get the nice, soft, beautiful, proteinaceous, easy to work with kinds of plants, and they will take over from the thistly, thorny, creepy-crawly, difficult types of plants to manage.

So viticulturalists should be prepared to invest a bit of time at the beginning if the soil isn’t healthy already. And is there anything specific to vineyards that viticulturalists need to understand about cover cropping – is it much different to cover cropping for farms?

BC: Not particularly, but the height of the type of plant and whether it’s an annual cropping cycle or a perennial, and its degree of maturity so that it can become reseeded, so you don’t have to reseed it annually – at least not with all of the species…

We use early season grazing of sheep and goats at high density, quick rotation so that they aren’t over-grazed but just appropriately grazed. The sheep actually stimulate the regrowth of the cropping system, so it responds as the season advances into the summer time with a good early maturity. Then, in many cases where it’s just mowed, what you end up with is all of this reflective strawy grass on the soil surface – not just grass but all the plants that turns golden as it dries out – and it reflects heat back up to the fruits underneath the canopy and actually increases the warmth and the dryness of the canopy. This reduces the incidents of mildew, and stimulating this broad array of canopy biology that additionally enhances the resistance of the plant through species competition of one dominant mildew type problem.

That’s a unique benefit of cover cropping, or mulching. And Bob Shaffer, do you want to add anything? 

BS: We have to recall that viticulture is a monoculture, often times at least, and I see the cover crop as a way to bring diversity, and to break the problems that are associated with monocultures. Also, I can rotate the genus and species that I use; I can rotate them over space, I can rotate them over time, so it actually adds, not only diversity to the monoculture, but adds the component of rotation. For example, I can put perennials on one side of the vines or tractor rows; I can manage that as a perennial cover for a few years, and then I can have annuals on the other side. I can also use those annuals and/or the perennials – or specific strips planted through the vineyard – as a beneficial habitat and food sources for beneficial insects, beneficial life forms in the vineyard. So, in all ways, the cover crop – if selected and managed well – can be the source of diversity, can be the source of rotation, and the source of beneficial life forms brought to the vineyard.

There are many variables when it comes to cover cropping, and there is no “one-size-fits-all” approach, but is there something you would recommend to everyone starting off with cover cropping?  

BS: It’s something that teaches you. I’d encourage people to immediately start cover cropping, and all farmers must always have trials going on. These do not have to be large, expensive, exhausting procedures, but having some type of trial always going on in the farm shows you where to head next. It also is your little classroom where you can go out and look and learn. So having at least some strips of cover crops – of different species always – to learn what to plant next is a good idea.

There are a lot of species to choose from as well. Bob Shaffer, what are your thoughts on choosing the best species for vineyards?

BS: On choosing species, one of the things you want to do, as Bob Cannard pointed out, you want to use a polyculture. I’m always going to use a mix of grasses, legumes and forbes when I’m planting. Also, as we broadcast it or drill this type of mix, the site itself will sort out which plants are most appropriate there.

In frost-prone vineyards, cover crops may the increase in risk of frost damage. What is your advice regarding this?

BS: Certainly if I’m going to put a cover crop into a frost prone vineyard, then I’m going to add the important component to the cover crop that we haven’t directly mentioned yet, which is as important as species selection, or any other feature of the cover crop: the management of the cover crop. So, if I have frost concerns, I’m going to select cover crops that are low growing, and then I can manage the cover crop in the frost season by further mowing it – at least on one side of the rows to allow some air drainage. Also, if you’re using broad-leafed species, they tend to have less of the ice nucleating bacteria on their leaf surface, and are less prone to causing frost problems in the vineyard or orchard.

I want to address another common worry that people have regarding cover crops, which is water usage. Wouldn’t cover cropping add extra irrigation costs for drier climates?

BC: We grow over-winter cover crops and we utilise rainfall as a natural irrigation, and it actually increases rainfall infiltration by reducing soil compaction. So actually, we reduce irrigation requirements; and then, it’s depositing on the soil surface at maturity, high levels of carbon, and one unit of carbon will support and hold approximately eight units of water. So, we increase our water holding and infiltration characteristics by increasing the organic matter content and the root zone development through cover cropping.

Yes, I read in a couple of articles, including a 1994 research article in the California Agriculture journal, that winter crops generally have very little impact on soil moisture compared to summer cover crops – so that would be a good option for vineyards. And Bob Shaffer, do you have anything to say about water usage or to add to Bob Cannard’s point?

BS: The cover crop, particularly because of its roots being in the ground, increases the humus levels. As those roots decompose, it increases the humus level, and this is the material that Bob Cannard was referring to as holding more water in the soil.

Though I will say that, sometimes if I have an existing vineyard, maybe it’s old and maybe the soil is weak and worn out, the transition period of introducing cover crops into that vineyard – there has to be some care taken to make sure that we don’t take water away from vines. Obviously, a cover crop plant uses some water when it grows, but it’s more an issue of timing: both timing in terms of transitioning into a cover crop (where the vine gets used to having other roots around it) and also as we build humus in the soil, there’s a little transition time that’s needed for that. And then, if we use a little water in the spring time for the cover crop, that doesn’t take away critically from the other crop – whether it be vines or some other plant; but later in the year, as the cover crop has been managed into a mulch, we’re actually using less water because we’re protecting the soil surface, we’ve built humus in the soil… And so, the timing issue on water needs to always be addressed rather than saying “okay, does the cover crop use water or not”.

So the takeaway from this is that timing is everything and it may increase water usage at the beginning, but in the long run it will actually save water. And now onto the management question: I presume it takes a little more time and effort to manage cover crops – wouldn’t this increase management costs?

BS: Considering whether cover crops raise our management costs, we have to look at the whole farm, and look at the multiple benefits that the cover crop has brought to the farm to address whether we lost or benefitted in terms of management dollars.

Can you both give me some examples?

BC: Well, my field, these vineyards that I assist in managing were conventionally grown and heavily cultivated, and herbicided underneath the vine rows. And we had, when I first took over twelve years ago, a preponderance of tenacious, noxious weeds that interfered with the canopy of the grape vine, and through management of the cover crops – planting selected varieties and improving the soil, and utilising inter-crop grazing of the sheep and the goats – after twelve years now we have very few noxious weeds and it’s actually reduced our over all costs; weeds that would shoot up from the herbicided strip into the canopy that had to be mowed or supressed in one fashion or another.

BS: Another aspect of management that cover crops can safe you money instead of cost you money would be for dust control, for example. A lot of times a vineyard or farm will get very dusty during the dry season, whereas if we have cover crops and we’ve managed over to stubble and/or mulch on the surface, it reduces dust. That dust can increase mite pressure in the vineyard, so if we have mulch and we’re absent of the dust, then it decreases our cost of spraying for mites, or managing for mites. There a number of other features that we could name that the cover crops actually decreases management costs.

One of the benefits I came across was the introduction of beneficial predator insects that keeps pests down. Has that been your experience?

BC: We’ve had very few problems with pests.

BS: Certainly, if you provide habitat and food for everyone, then the system tends to become more balanced. Where there are appropriate numbers of predators, there are appropriate numbers of prey. As the goal in “managing the farm” or “managing pests” is not to eliminate all the pests; it’s simply to increase the antagonism from the pest’s predators. And we do this by carbon, we do this by having flowering plants; nectar, pollen, habitat, and carbon above ground.

If anything, I’ll say the cover crop, with all the glory that we’ve talked about and the beauty of the cover crop, still: the cover crop shouldn’t be viewed as all we need; we always have to look after the whole system and say “okay, look: I’m going to manage organic matter, which includes cover crops, compost and mulches. I’m going to manage minerals. And I’m going to manage my tillage”. Those three areas: OM management, mineral management, and tillage management all need to be considered, all need to be cared for to have the cover crop show its best; to have the compost to show it’s best, and to have the minerals show its best. They’re linked in biology, they’re linked in being foods, and they’re all necessary to manage at the same time to get the best benefits.

So a holistic approach is really what you’re going for. And are there any other benefits to using cover crops that would outweigh other management costs?

BC: The cover crop and the soil surface organic material holds and supports the soil, where many clean, cultivated and just bare soil surfaces can be very tacky. Let’s say during harvest we have modest rainfall, then it impedes the ability for the harvest crews and the equipment to move through the vineyard because of the muddiness, whereas with the increase of soil surface organic material (and especially the dry carbonaceous material), the soil surface is held and supported by the residual root systems. And the soil surface itself is protected by the strawy organic material, and this really reduces the stickiness in many different ways: just physically at a large-scale straw level, and at a digested carbon level/humus level it allows the soil particulate matter to be happy with itself and want to stick to other elements, such as harvesters feet

That’s an interesting benefit that I wouldn’t have thought of, actually.

BS: That’s actually a huge benefit, even during the year sometimes with the irrigation systems, if you have cover crops it enables workers to have less mud on them, and to have some place to sit down; to have some place that’s green and flowering instead of just a bare herbicided soil. There’s a huge difference in the vineyard for both the people and the crop when we use cover crops.

We’ve covered a lot of ground in this episode already, although we could probably go on forever. But for the final question: are there any issues you want to address with cover crops, or anything else that viticulturalists need to keep in mind when cover cropping?

BC: Well, it’s a possibility that you might have overgrowth. A lot of viticulturalists, back to frost issues, are worried about canopy heights of cover crops. Well, there’s legitimacy to this, because it reduces air drainage, but at the same time, a high-density cover crop of good, bread-leafed plants has a better canopy biology to it that resists frosting. And those plants are also respiring energy and actually warm the vineyard’s atmosphere on cold nights.

No, there are definitely problems, and it’s a progressive activity. A novice viticulturalist beginning to grow cover crops might be afraid to let them come to maturity, and boy, that’s all right – it’s a beginning. And as we develop and grow, we develop more confidence as we grow, and we also develop our soils and select a broader diversity of cropping specimens, a variety, and allow them to come to greater maturity.

BS: That’s certainly experience speaking, and I’ll say to summarise that excellent comment by Bob Cannard: I would encourage people to view cover cropping as a transition, as part of a transition into more healthy soils, and to better above-ground relationships, rather than an instant change.

Well put. So, cover cropping is definitely beneficial, it just takes a little bit of time and a little bit of effort to get it all going. But once you have the experience, it’s probably the best way to go. Unfortunately that’s all we have time for I’m afraid, thank you Bob Cannard and Bob Shaffer for coming on the show.

BC: Well, thank you for your interest.