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Cultivating Questions Rotation Cover Cropping for the Small Fruit Orchard

Cultivating Questions Concerning the Bioextensive Market Garden

Rotational Cover Cropping in the Small Fruit Orchard

Dear Anne and Eric:

Belated thanks for your video. I’ve been enjoying it very much. I’ve been planning my own small farm system and yours is an excellent model. I will be using horses and, as such, am planning the layout accordingly.

I have a question regarding soil building, soil maintenance, and moisture conservation between rows in a small fruit orchard. I am considering an acre of Saskatoon bushes (I believe you may know this as a “service berry” in your neck of the woods). At any rate, the plant is a native to our province and there are a few cultivators used commercially.

I plan to plant the trees such that the ground can be cultivated in both directions. I am toying with establishing a half-acre of raspberries in the “hill” system so a similar two-way cultivation is possible.

My question concerns adapting some aspects of your summer fallowing using double-cut rye (or a similar plant) between the rows in the orchard. Would the rye steal moisture from the bushes and canes of the fruit? Would it be practical to plow under the sheet composted rye due to the roots of the orchard plants? Could an adequate incorporation of plant material be achieved using a disc harrow versus plowing? Would it be prudent, in a more or less “permanent” summer fallow as exists between rows in a small fruit orchard, to rotate cover crops and include leguminous varieties in the rotation?

My aims in this are two-fold: 1) to maintain fertility and control weeds in the orchard; and 2) to provide ongoing work for the team. Any suggestions or references would be greatly appreciated. I hope your growing season goes well this year.

Sincerely,
Scott Duncan
Edmonton, Alberta

Unfortunately, we have never had the pleasure of meeting a Saskatoon. And our relationship with raspberries has been limited to a couple of 100′ rows in the house gardens. Nevertheless, we feel pretty certain that rotational cover cropping with horses could be adapted to a small fruit orchard.

Cane fruit are among the most moisture demanding crops in the market garden. So, if irrigation is not available, it is essential that the cover crops grown between the rows do not compete with the berries for moisture. For example, a cover crop of oats and Canadian field peas planted right after the harvest of summer bearing raspberries would not compete with the cane fruit during the main growth and fruiting period.

When planted in early August in our area, the oats and peas put on a lot of top growth before freeze up, suppressing most fall weeds and providing complete ground cover. These spring annuals die back over winter so it is possible to incorporate the winter-killed residues fairly easily the next year with a horsedrawn disc – and without causing much harm to the roots of the small fruits.

Working the ground at this time of year would set back most spring weeds as well as any volunteer canes invading the alleys. Depending on the degree of weed pressure, the alleys could be cultivated or mulched during the summer harvest period, or seeded down right away to a slow establishing cover crop like berseem clover. This southern legume dies back over winter in more northerly climates just like the oats and peas. They also fix nitrogen and would add some diversity to the overall cover cropping scheme.

Mixing annual ryegrass in with the clover would make a tougher sod and improve soil structure more than using the legume alone. Other rotational cover crop options for summer bearing cane fruit grown in the North might include deep rooted sorghum-sudan grass, forage soybeans, Japanese millet, buckwheat or cowpeas.

For any of these rotational options it is critical to time the planting of the cover crop so that it frost-kills before setting viable seed. In this regard, we advise experimenting with these alternatives on a small scale at first to make sure they perform as expected. For example, we learned the hard way that in years with plenty of snow cover, berseem clover does not reliably winterkill in our area. Annual ryegrass also keeps us guessing: if planted too early here it may set seed in the fall; if planted too late it may survive the winter.

Really, all of these suggestions for cover cropping between the rows of summer raspberries is pure speculation because we only grow the fall bearing varieties. We decided to go with the fall berries for a couple of reasons. First, a fall harvest avoids the worst of the ravages from the Japanese beetles. Secondly, fall bearing varieties, like Heritage or Autumn Bliss, do not require pruning or trellising. Instead, we just mow off the canes with the team and the sicklebar mower after the ground freezes hard. Removing all the canes from the garden each year seemed liked a good way to minimize disease. The big disadvantage to fall raspberries in our area is that sometimes we lose the last part of the harvest to frost.

Cultivating Questions Rotation Cover Cropping for the Small Fruit Orchard
Cultivating spring spinach between the two rows of fall bearing raspberries in the house gardens. After the spinach harvest, we mulched the alleyway with old hay to conserve moisture and protect the soil overwinter, then mowed the canes with the team once the ground froze hard.

We confess that we have not yet developed an ideal cover cropping scheme for these fall producing varieties. We tried planting the alleyways to oats in the fall for several years, but the timing of this cover crop coincided with the fruiting period of the berries and the tall top growth sometimes got in the way of the harvest. On the other hand, we were afraid that a spring planted cover crop would be too competitive with the growth stage of the canes. We ended up growing spring cash crops in the alleys, like lettuce or spinach, then followed with a heavy mulch of old hay to conserve moisture and smother weeds during the latter part of the growing season. The major drawback to this practice over the course of the years turned out to be compaction. Without the soil structuring root system of the cover crops, the ground in the alleyways became harder and harder.

For this reason we intend to try cover cropping the alleys once again in the new patch of fall raspberries we planted last year. This time we plan on using an overwintering annual like rye. Our hope is that if we can get the rye established during the start of the fall harvest that it won’t compete much with the berry crop and still provide plenty of winter cover. Then, the next spring, the rye should produce a significant amount of biomass before the new canes really start growing.

We plan on clipping this overwintering cover crop with the team after it reaches its full height and begins to drop pollen. Mowing the rye at this time kills it completely before it can mature viable seed. And raking the straw-like rye residues into the rows would help hold in summer moisture for the major growth phase of the canes. If raking the 4-5″ long stems turns out to be problematic, we might try the double-cut rye described in the Spring 2000 column.

Either way, one of the advantages of mow-killed rye is the dense root system dies and decomposes fairly quickly after severing the top growth. So within a week or two of mowing and raking the biomass next to the base of the canes, we should be able to work up the rye stubble in the alleys with the horsedrawn disc. This would commence a brief summer fallow to clean up the weeds and the invasive canes before seeding down these between-row areas to the next overwintering cover crop in the rotation.

Now this time around, we might try other winter grains to add some diversity. Triticale, winter wheat, and spelt are some of the overwintering cover crops we have trialed in the market garden in recent years which would be suitable for intercropping between the rows of fall bearing canes. (The most rewarding discovery was finding that a mixture of rye and spelt significantly increased the total biomass produced under the double-cut regimen because the spelt started growing almost two weeks later than the rye in the spring.) If we can get the cover crops seeded early enough in the alleys between the fall berries, we might also mix in some overwintering annual legumes like hairy vetch. Austrian winter peas, or sweet clover (which behaves like the winter annuals even if it is classified as a biennial).

Jim Fulmer of Hoskins Berry Farm in Philomath, Oregon has taken the idea of cover cropping the small fruit orchard a quantum leap forward by establishing perennial cover crops in both the alleys and the rows. According to his article in the July/August 1999 Biodynamics, Jim mows and blows the living mulch grown in the alleys right into the crop rows, in this way suppressing the weeds and white dutch clover growing next to the plants. The timing of the mowing and blowing takes into account when the cane fruits have the greatest demand for moisture. Concentrating the biomass grown in the alleyways around the base of the canes has significantly improved the fertility and biological activity in the fruit growing areas.

As for other examples of small fruit orchards or vineyards where cover crops are utilized to control weeds, improve soil quality, and provide habitat for beneficial insects, check out back issues of Biodynamics and Acres-USA. Better yet, for a comprehensive — and, frankly, inspiring — introduction to the many uses of cover crops in both annual and perennial cropping systems, we highly recommend the new bulletin, “Naturalize Your Farming System — A Whole Farm Approach to Managing Pests” from the Sustainable Agriculture Network.

Be forewarned that much of the recent experimentation with cover cropping in perennial systems assumes that irrigation is a given. Motorized equipment is also the norm for incorporating cover crops in the narrow alleyways or for mowing and blowing biomass into the fruit rows.

To accomplish the same thing with horses, it may be necessary to plant the rows at least 15′ apart. This spacing would allow 10-12′ between the rows after the canes have filled in, enough room to mow the alleyways in both directions with a 5 or 6′ sicklebar. These extra wide alleys would also make it possible to use the horses and side delivery rake to move the cover crop residues to the base of the canes to serve as a mulch.

If the fruit rows, or hills, were planted even further apart, it might even be possible to develop a full blown rotation of cover crops and vegetables in between the perennials just like we do in each half acre strip in the bioextensive market garden. This arrangement would provide the most diversity and flexibility — and the most opportunities for working the team.

We must admit that we feel mighty uncomfortable making all of these suggestions about cover cropping between perennials without much in the way of firsthand experience. What we can say with authority from the last eighteen years of farming is that the summer fallow, combined with rotational cover cropping, is a very effective way to prepare the site for a new orchard. We have used this strategy right from the start before the small plantings of raspberries as well as other perennials, like strawberries, herbs and asparagus. More recently, we prepared a weed free and fertile site for a small apple orchard using both cover crops and the summer fallow as documented in the accompanying photo essay.

In conclusion, we can recommend the following with confidence: using the summer fallow and cover crops to build up the soil and reduce weed pressure for a year or two before planting the cane fruit, or Saskatoons, will ultimately save a lot more time and energy than trying to employ these techniques after these perennials have been established. We might add that working the land for a year or two before establishing the small fruit orchard might benefit a young team just as much as the berry crop. At the very least, it would be a good idea to familiarize the new horses with the implements in a field situation before putting them to work between the rows of small fruits.

Cover Crop Possibilities for Cane Fruits

Summer Bearing Raspberries

Spring – Disc in the winterkilled oat and pea residues and cultivate as necessary to setback spring weeds and the canes invading the alleys.

Summer – Cultivate the alleyways, for weed and moisture control. Reseed the alleys to the next winterkilled cover crop as weed pressure and the harvest permits. Consider alternatives to the oats and peas this time around, like annual ryegrass and berseem clover, or sorghum-sudan grass and forage soybeans.

Fall – The cover crops put on the bulk of their growth after the berry harvest so they do not compete with the canes when they have the greatest demand for moisture and nutrients.

Winter – These frost-sensitive cover crops die back with the first hard freezes creating a mulch that protects the soil and traps winter moisture. Now is the time to prune out the old canes.

Fall Bearing Raspberries

Spring – Mow rye when it begins to drop pollen and rake the strawlike residues into the crop row to serve as a moisture conserving, weed suppressing mulch for the canes which are just starting to row.

Summer – Disc or harrow the mow-killed rye stubble to control weeds in the alleys and initiate a brief summer fallow. Meanwhile, the canes go into their growth surge without competition for moisture or nutrients.

Fall – Seed down the alleys to the next overwintering cover crop as the berry harvest gets underway. This time, try mixing in some triticale or spelt with the rye. Or experiment with winter annual legumes, like hairy vetch and Austrian winter peas if the cover is seeded at least 40 days before the first hard frost.

Winter – The overwintering cover crops have already formed a tough sod, preventing erosion and rebuilding soil structure. These covers will put on the bulk of their top growth in the spring before the new canes need much in the way of moisture or nutrients. Winter is a good time to mow the old canes and remove them from the field for disease control.