Economic impact of cover crops and compost in orchard systems

From the podcast interview with Mike Omeg. A longer read, and very much worth the researched perspective.

John: Can you tell us about some of the things you tried that perhaps didn’t work so well, and then what you eventually ended up doing?

Mike: There are a lot of things I tried that didn’t work out well. We all like to talk about the successes, but oftentimes we can learn a great deal from failures. It was a mixed bag―like anything that is worthwhile, this was a complex project.

We started learning how we could enhance our soils and things we could do to boost our plants. One of the challenges that we had was how to scale that up―how to go from techniques that worked in, say, a small market garden―where the grower is selling directly to consumers and maybe only working part time―and scaling that up to the size of operation we have, which is 350 acres of fruit and 1,800 tons of fruit produced every year.

We started out with things that we thought would be simple and easy. One of those was putting compost on all acres that we have under management. We set a timeframe, because we couldn’t apply compost on all of those acres. What we found was that the logistical expense of moving thousands and thousands of yards of compost was huge. We had to go to the Portland metropolitan area, which is about 80 miles away, to get the volume of compost we needed. Getting that compost here, paying for the trucking, paying for an area where you can load that much material, buying or renting equipment that was out of our norm―bucket loaders and that sort of thing―became a real challenge for us. It was a really massive operation. It was a lot of diesel and a lot of steel, and that is not where I wanted to go with bio-intensive management of my farm.

I think that the compost did work for us. But if I were to do it again, I would have taken that capital that I invested in the compost and put it into other materials that we produce here on the farm or from other techniques. I think we could have probably had an equal or better return on our investment with a lot less giant equipment rolling up and down the roads and our orchard rows.

John: If you were to do it over again, where would you prioritize? Where would you focus, based on what you’ve observed?

Mike: I think that if I were to start at day zero again, in this process, I would focus a majority of my energy on mulches. What we learned over time was that the primary benefit we received from the compost was getting the soil underneath the tree covered with an organic material.

It didn’t matter as much what material was on top of the soil. We put pine chips on top of our soils. We put straw on top of our soils―wheat straw and grass-seed straw. What I found over time was that the compost was of course contributing nutrients. I love compost―but in my flower pots, not on an orchard scale.

The material we were applying wasn’t great compost. It wasn’t a super powerful compost with those humic components that we needed. It was really serving as a mulch. It protected the soil from the sun and from irrigation―the physical damage that irrigation causes.

In our orchard systems, we maintain a permanent side alleyway in between the tree rows. For generations, our family has been mowing that alleyway―like many other growers―and leaving the clippings sitting in the alleyway. What I arrived at was that if we could move that grass that we cut and windrow it right in the tree row, and cover the soil in the tree row, we could accomplish similar results to the compost with a fraction of the land, labor, and capital investment of the compost with practice we were already doing―mowing our alleyway rows.

If I were to pick one thing that we landed on that improved upon the compost, it would be to mow and blow. During the growing season we throw our grass clippings right onto the tree row. With cherries and other tree fruits, pruning is a very, very important process. We do it during the winter, during a dormant period of the orchard, and we generate a huge amount of carbon in the form of cut branches that we stack in the alleyway. And just like the grass, we used to mow that down and just leave it there.

But with mow-and-blow, we’re able to shred those prunings and move that carbon source over into the tree row. That’s a technique that really pushed us forward―getting the soil covered. I think that it allowed us to then put some very focused and very fine-tuned applications of nutrients and biological stimulants onto the soil―onto that mulch―and get a very rapid response, without the big earth-moving equipment that the compost required.

A valuable compost in our system is a very intentionally made, refined compost that can go on at a fraction of the amount that we applied when we used to buy thousands and thousands of yards of municipal compost. Instead, what we started doing was making a very small amount here on our farm―a nutrient-focused compost that incorporates nutrients we know we need. We put that material on in small amounts and get a lot more bang for our buck, because that compost is really a nutrient input instead of a mulch.

John: You’ve identified mow-and-blow as being foundational to building a soil cover within the tree row. What are the possibilities of using cover crops and producing even more biomass for that mow-and-blow operation, in addition to the grass that you’re growing?

Mike: We have begun to utilize cover crops in our alleyways. We maintain an alleyway between the trees that we can drive up and down. You need to have some kind of crop that’s growing there to hold the soil in place so that it doesn’t erode―to keep your orchard from turning into a dust bowl. We don’t want to have thousands of small dirt roads going up and down our alleyways, because that creates a giant dust plume that is bad for everybody, especially the soil and our trees.

We have maintained sod―a perennial ryegrass with creeping red fescue. There are orchardgrass sods. Many growers have their own favorites. That sod does its job―it holds the soil in place and keeps the dust down. But it does not contribute a whole lot to the trees. After we landed on the mow-and-blow technique, we started blowing what we already had in the alleyways over into the tree line. But I began to wonder if that was the best way to do it.

We eventually began to explore cover crops in order to generate more biomass in the alleyway and to transfer that biomass using our mowers over into the tree row to act as a mulch. We started cover cropping on fallow fields that were waiting to be planted. We would maintain cover crops there, and we had various mixes of plant species that we utilized. We just took the plants that worked in our fallow fields and started putting them in the alleyways.

We had some successes and some failures with that, because a big, open field with no trees growing above it is a very different environment for sun-loving cover crops than the shade of an orchard canopy in an alleyway. We have found a series of plants that we really like to put into our alleyways that generate a lot of biomass during the dormant season―basically from fall until spring. We don’t have a lot of equipment passing over our alleyways during that time, so the cover crops have an opportunity to grow.

Then in the spring, before we start our orchard management activities, when the alleyways are quite busy with equipment, we take that cover crop that grew over the winter and that generated a lot of biomass and we blow it into the tree row, and it generates a good start to our growing season for the cherries when the soil is starting to warm up. It gets this very nice coating of a diverse-species mix of mulch on top of it.

John: Mike, when you grow these cover crops during the winter months, doesn’t it have the effect of then choking out the sod? How do you manage that? Do you still have a sod for the following year?

Mike: We maintain two crops in our alleyways each year. We have an overwintering cover crop, and then we plant a fast-growing temporary sod. I don’t know if it would be proper to call the cover crop that grows during the warm season in our rows a true sod, but we maintain a green crop there. But it’s not grown as a cover crop because it’s very difficult to generate a whole lot of biomass when you have so many equipment passes going up and down the rows from May through August.

We were never able to find a warm season crop that we could plant and grow as a cover crop that would generate a lot of biomass. We just have too many different-sized pieces of equipment. By the time you take all those tire tracks and draw them out going down the alleyway, we really only end up with about 24 inches, right in the very center of the alley, where anything has an opportunity to grow. And keep in mind that it can’t grow that tall because the crown of the plant is constantly getting batted down by equipment passing over the top of it.

John: What you’re describing, if I’m understanding it correctly, is that you actually plant two crops―you plant what you’re considering a cover crop in the fall to produce biomass during the winter months, and then you’re planting a soil cover, or a ground cover, in the spring. Is that right?

Mike: Yes, that’s exactly what we do.

John: Can you tell us a little bit about the cover crops that you ended up selecting, particularly for winter cover? What was the rationale for those?

Mike: It was really difficult, because when I began my research, I quickly found that there was a giant laundry list of species that are available to us as growers. Keep in mind that our focus has been on what works―if it will sprout and grow and accomplish our goals.

It was very difficult to find anybody in orchards who was doing what we were. There was nobody I knew of that I could call and talk to and have an in-depth conversation about what species they were planting. There were people that were planting cover crops in fallow fields, but there wasn’t anyone who was planting them in the alleyway.

So, I took the species that grew the best in the fallow fields and tried them in the alleyways. I found that not every species did well; in fact, most species didn’t do well. But the species that we landed on, that did do a good job in the alleyways, really do a good job.

The mix we like in our alleyways is a mix of annual rye―all the row crop growers are maybe cringing when I say that, but it’s not a problem for us in our perennial system―with triticale, and then a mustard species, a hybrid forage kale, and a tillage radish. Those species work really well for us.

You might notice that I didn’t name a legume in that mix. That’s because we had difficulty finding a legume that would work in this application. We tried lots and lots of different ones, but we were never able to find one that worked for us. When we were evaluating legumes in our fallow fields and in our alleyways, voles and gophers would become a real issue for us. They were very attracted to the legumes. I avoided those because we didn’t find one that worked well, and the vole and gopher problem they generated was a big deal to us.

John: When you say that you didn’t find a legume that worked well for you, what were the parameters and characteristics you were looking for? Was it just because of slippery slopes? What were the constraints on the legumes, other than the gophers and the voles?

Mike: We evaluated a lot of different clover species. We found that they just didn’t establish well for us, consistently. When we talk about having a return on our investment, we need to have every seed that goes into that mix work―it needs to earn us a return. We just did not have consistent stands of clovers become established.

We did find that vetch could work for us. It would establish and it would grow, and it would be a benefit. But here’s the catch: it’s just not very well behaved at staying in the alleyway. It would take advantage of that nice open space underneath the tree, where it didn’t have competition from its companions in the alleyway. It would grow into the tree row, which would be fine until it would encounter a micro-sprinkler. We irrigate almost all of our acres by drip or micro-sprinkler irrigation. When that vetch vine would encounter the micro-sprinkler, it would whip up around it, and it would make the micro-sprinkler ineffective because it would cover the sprinkler. Because I couldn’t make vetch behave, I was forced to eliminate it from our mix.

John: Have you considered growing any cover crops in the tree row? Is that a possibility?

Mike: That’s something I would love to have happen for us. It seems so incredibly simple to say. Why can’t we just grow something in the tree row? Yet it is incredibly, incredibly complicated to find something that works.

I have tried countless species and countless mixes to grow underneath our trees in the tree row, and I am yet to find one that works really well. I’m sure people are wondering, “My gosh, what do you mean? Just look at all those species that you could plant.” But it is very difficult to find a plant that stays low enough to not interfere with our micro-sprinkler irrigation and that can grow well.

There are areas of the tree row that are in full, blazing sun all day, and yet that species also needs to be able to grow right up to the trunk of the tree, which may be in full shade for almost the entire duration of the day. Most importantly, it has to compete with weeds that grow in a tree row―weeds that we unfortunately can’t allow to be there because of the micro-sprinkler irrigation.

John: And it has to survive being buried underneath the mow-and-blow mulch and still emerge and remain short while doing all those things.

Mike: Yes, and handle foot traffic. There’s not a lot of foot traffic in the tree row except during harvest. Then, several hundred people enter a small block, and those people have to trample around the tree to get the fruit picked. That tramples a lot of cover crops.

I have not yet found the plant that accomplishes everything. There are things that grow beautifully underneath young trees―trees that don’t have a big canopy and aren’t in production. But as soon as those trees get up and start to shade―as soon as we start having pruning activity―we would trample those cover crops down. The mow-and-blow brings a whole new dynamic because there’s nothing I have found that will not interfere with the micro sprinklers and that can take that mulch getting put on top

I’m open to any ideas. There are a couple of species that do okay. But to plant hundreds of acres of them is impossible. They may be a tuber, or they may be a bulb, or we may need to start them as a small potted plant. That’s practical under a few trees or in a backyard scenario, or maybe a smaller orchard. But when you talk about hundreds or thousands of acres, you could be talking about millions of plants, and you can’t find a horticultural nursery that could produce them for you economically. It’s a real challenge.

I found some species that I thought were great. But after we got a foot of snow on the ground, the gophers also thought they were great, and they were gone come spring.

John: It’s an interesting set of challenging conditions. Can you tell us a little bit about some of the species that you experimented with that were tubers or potted plants?

Mike: I can. Three of them did a good job, but we just weren’t able to scale them effectively. One of them was ajuga―Ajuga reptans. We planted not the variegated types or anything―the fancy ones―just the wild type. The second plant is moneywort―Lysimachia nummularia. It worked quite well. Again, it was just something that was impossible for us to scale. And then the third species is a non-hybrid comfrey―Symphytum officinale var. patens―that we found worked very nicely.