Improving Orchard Management through Multi-Species Cover Crop Mo

Planting Equipment

1. ATV-mounted broadcast seeder. We quickly abandoned the use of the ATV in favor of the other two pieces of equipment.  The Cabela's ATV Spreader and Feeder was difficult to calibrate and did not distribute the seed evenly, leading to inconsistent stands.  Maintaining a constant speed in the orchard was a challenge that we never fully overcame.  A smart phone with a GPS speed app worked great, as our ATV does not have a speedometer, but the uneven terrain and need to avoid obstacles, such as hanging branches, made it difficult for the operator to maintain a constant speed.  This method also required that the ground be tilled before application, which meant a tractor and tiller quickly ate up much of the equipment operation and labor savings from using the ATV and seeder.  We tried seeding over newly mowed sod but the cover crop did not establish so we shallow tilled the alleyways first.  However, simply seeding over the tilled ground did not do well for us.  To get the best stands with the ATV required a second pass over the seeded ground with the ATV towing our Rankin drag mat we use behind our arena harrow.  Overall the only savings the ATV method offered was not having to purchase an expensive seeder or drill.  However, the cost of planting was higher than we expected as the ATV method required the most equipment passes and labor.  In addition the cost of seed was higher with the ATV because we had to increase our seed/acre to get full stands.  Generally the other equipment achieved the same stands with 30% less seed/acre.  If a grower does not have a drill but does have a tractor, tiller and ATV and is willing to purchase an ATV seeder then this method would work to establish cover crops in the orchard without having to purchase expensive equipment.

2. No-till drill. The Land Pride 606NT No-Till Compact Drill worked well for us.  It did allow us to plant into the alleyway without tilling the soil.  The unit was simple to calibrate and the seed was applied and emerged evenly.  However, the sod proved to be real competition for the cover crop.  We did not have any luck establishing a good stand of cover crop unless we killed the sod first.  We tried flail mowing the sod to the ground and planting immediately afterwards.  We also planted into the sod and then flailed.  However, neither method let the cover crop establish well enough to compete with the sod.  We tried two methods of “chemical mowing” the sod before planting: 1) apply a burndown herbicide and 2) apply glyphosate.  Both methods allowed the cover crop to establish far better than mowing.  However, the sod could sometimes outcompete the cover crop when a burndown was used.  Glyphosate worked very well at virtually eliminating the sod competition and allowing the cover crop to establish.  But applying these herbicides required another pass over the alleyway, a specialized boom setup (as orchards typically only spray the tree rows and do not have booms set for sod) and the cost of the herbicides.  The drill did allow us to plant the cover crop without tillage but to get the stands we wanted we had to use more equipment, labor and herbicides.  The drill was easy to operate and maintain.  The sod cutting discs did not need replacing even after 100 acres or so of seeding.

3. Power harrow with air seeder. The Moreni VITIS K power harrow and seeder proved to be the best setup for seeding the cover crops into the alleyways.  The APV PS 120 air seeder was very easy to calibrate.  The digital controls were straightforward and allowed for precise application of the seed.  We purchased a MX-35 add-on speed sensor after the 1^st year and really liked the additional features it offered.  The sensor allowed us to precisely apply the seed even when we had to vary the tractor speed due to terrain or obstacles (or operator error).  Maintenance of the seeder was easy and changing out of the seeder heads to accommodate small or large seeds was simple.  The power harrow unit did a great job of tilling even in dry and rocky soils.  We were able to set the unit depth to a shallow or deep.  We found that tilling to a depth of 3 inches knocked out the sod and provided a nice seed bed for the cover crop to establish.  Some spotty sod regrowth occurred but rarely did the cover crop not outcompete the sod.  When we compared the no-till drill with glyphosate sod kill and the power harrow we saw a much better stand of cover crop.  The better cover crop establishment is likely because the alleyways in orchards are very compacted from the many equipment passes (>12 tractor passes alone) that occur when growing the orchard crop.  The light tillage allows the growing cover crop to establish in an area that is not compacted.  The power harrow and seeder were easy to operate and maintain.  In our soils we found the blades needed replaced after about 50 acres of tillage.  An additional benefit of using this machine was that it leveled out the alleyway, reducing roughness of the terrain and thereby reducing equipment maintenance costs from “bouncing and shaking” over uneven ground.

^{No-Till Drill:  The Landpride 606NT No-Till Compact Drill was well sized for orchard systems.  The machine was well built and easy to operate and maintain.}

^{Drilling into sod:  The drill easily planted the cover crops into existing sod.  However, the stands established best when the alley was tilled before planting.}

^{Drilling into a tilled alleyway:  The drill worked well and the stands established best when the alley was tilled before planting.}

^{Drill planted stand:  A stand of drill planted cover crop mix 1 sown in the fall timing, early October.  The drill planted stands grew great but were the most expensive per acre for machinery and labor to plant.}

^{Power harrow seeding:   The Moreni VITIS K power harrow and APV PS 120 air seeder proved to be the best setup for seeding the cover crops into the alleyways.  It allowed planting the cover crop in a single pass.} 

^{Power harrow seeding into young orchard:   The power harrow did when seeding in freshly planted orchards or in rocky ground.  It was easy to operate and established solid stands of cover crop.} 

^{Power harrow seeding into sod:   We set the harrow to till to a depth of 3 inches.  This depth virtually eliminated sod regrowth and let the cover crop establish well while limiting soil disturbance.} 

^{Fall sown tillage radish:   The power harrow seeded this nice stand of fall sown tillage radish into sod.  With narrow spacing such as this we generally only made one pass with our seeder, which is 6ft wide, in the 10ft wide alleyway.}

Planting Date

We quickly learned a hard lesson about planting times:  spring and summer plantings do not work in producing blocks.  The multiple equipment passes over the alleyway from irrigation, pesticide applications, fertilizer applications, etc. knock down the cover crops, even low growing ones, to the point where the stand is very poor.  In addition, it is difficult to let the stands grow tall and to their full potential because they interfere with application of foliar sprays to the orchard crop.  There is also a safety issue with equipment driving over tall stands of cover crop on our steep terrain.  The cover crop can become slick and the equipment slides off the alley.  Even if the equipment passes over the cover crop are limited the shade from the tree canopy stunts the growth of the spring planted cover crop.  We tried only driving equipment on every-other-row but the cover crops still did not thrive from the heavy shading created by the neighboring trees.  The stands growing in shaded alleyways were had about 25% less biomass as stands in nearby non-bearing orchards where there was no shade.  Non-bearing orchards can be planted in spring, summer or fall because the equipment operations taking place on non-bearing acres is far less than producing acres and there is no shading.  The best time to plant in producing orchards is the fall, in our case early October.  For the most part all orchard operations are wrapping-up at this time of year and little to no equipment is driving over the alleyway.  Yet the weather is still warm enough for the cover crop to germinate and establish and irrigation water is available.  We found in every instance that the fall planting established the best stands of cover crop.  Even though orchards are pruned in the winter and the brush is shredded in the alleyway the cover crops seemed unaffected by this process.  We did not see any negative impacts on the cover crops after shredding brush in the alleyways.  We evaluated alleyways where brush was chopped and alleyways where no brush was chopped and found both cover crops always grew equally well when the spring temperatures warmed up.

^{A fall sown stand shown in winter:   This fall sown stand of Mix 3 had 45 days of snow on top of it a month before this photo was taken.  Fall planting were always successful for us.}

^{Brush shreddings on top of cover crop:   The fall sown cover crops always regrew well after brush chopping of prunings.  Here several inches of shredded branches sit above the cover crop.  Yet the following spring the cover crop thrived in this alleyway.  The stacks of unshredded brush awaiting the flail chopper can be seen in the upper right.} 

Seed Mix

We evaluated a number of species and found some worked better than others.  Several did not work at all for us.  The mixes worked great and we refined our species over time into “Mix 3”, the reasons for which are explained below.  Seeding rates are listed under the “Expenses” section of these results.

Although ‘Bounty’ Ryegrass and ‘Enricher’ Radish would establish solid stands for us when planted as a single species we preferred the mixes.  When we planted Mix 1 we observed that the subclover and Ethiopian cabbage did poorly for us.  So we eliminated them from the mix and created Mix 3.  Mix 2 did well but produced far less biomass for us vs Mix 3.  We found Mix 3 to be the best overall mix for us.  It provided economical cost/ac for seed, established readily, especially at the fall planting time, which works best for producing orchards.  The species in Mix 3 were able to handle occasional equipment traffic and all did fine even when brush chopping took place over them in the winter and very early spring.

^{A young stand of Mix 3:  We found that Mix 3 did best for us.  The combination of species germinated well and was cost effective.  It produced a considerable amount of root growth in both fine and giant (radish) size and an abundance of above ground biomass.  In addition bees loved the flowers of the brassicas if they were allowed to bloom.}

^{Fine roots shown growing where a small rock was removed.}

^{A young stand of radish.  The radish proved cheap, reliable and effective when planted as a single species or a mix.}

^{Mature tillage radish:  This fall planted radish shown 60 days later.  The growth of the radish was remarkable.}  

^{Freshly winter-killed radish:  Radish generally grew into January when the temperatures dropped enough for them to winterkill.  An occasional radish would survive all winter.}  

^{Radish root holes:  The holes that winter-killed radish left behind were numerous.  Some like the top photo were huge.}

^{A small roots from close-by plants that survived the winter were commonly seen growing down the holes left behind by  the radish.}

Leaf, Shoot and Fruit Sampling

Leaf Samples: We did not detect any differences between leaf samples in the trees over several years of data collection. 

Shoot Extension: No differences in shoot extension or caliper were observed in the trial between treatments.

Fruit Sampling: No differences in fruit size or firmness was detected between treatments. Yields were visually estimated to be the same.

Soil Sampling

1. Soil Samples

Below are the average nutrient levels from soil samples taken in the alleyway.  We present N forms, P, K, Ca, Mg and S as those are generally considered the most important nutrients by local orchardists. We do not believe these differences to be significant.  We did not see difference in nutrients between plating equipment used.

2. Penetrometer

The cover crops had a positive influence in soil compaction based on the penetrometer readings.  All of the cover crops reduced compaction vs the sod cover crop.  The radish single species lead to a significant reduction in penetrometer readings.  In the table below are the pressure at 6 inches depth.  We felt this would limit the influence of light tillage on the readings.

3. Soil infiltration

The cover crops increased infiltration rate in the alleyway soil.  The single species radish had a particularly dramatic increase in infiltration rate.  This is understandable as it was sometimes hard to find an area to test that did not have a radish root hole in the soil.

Expenses

Seed costs.  The rate and cost per acre of each cover crop treatment is outlined below.  Note that these costs are for each planted acre of cover crop.  To calculate cost per acre of orchard the grower would need to calculate the % of their orchard acre that is alleyway and multiply that into the cost.  For example: If your alleyway is 10 ft wide and your tree rows are 16ft apart then the % alley = 0.625 or 62.5%.  Therefore for mix 3, which is $42/cover crop acre would cost the grower $42 x 0.625 = $26.25 per orchard acre.

Planting costs:

Planting costs varied considerably depending upon the machinery used.  Our costs calculations for each of the machinery are noted below. 

We did not figure the cost of purchasing or renting the equipment into our study as the per acre costs would depend upon the number of acres treated.  However, the equipment costs are listed below for reference:

• ATV seeder - $250
• No-Till Drill - $15,000
• Power Harrow and Seeder - $11,000

Additional Labor/Management:

There was no additional labor or management for the cover crops vs sod.  Weed control was never an issue in any treatment.

Income:

As there was no difference in fruit/size or quality there was no increase in income using cover crops.

Mow and Blow

By the third year of the project the lack of response in shoot growth and fruit size/quality from the cover crops was perplexing as there were measurable improvements in the alleyway soil from the cover crops.  The data collected from the penetrometer pressures and soil absorption rates clearly showed the soil in the orchard was improving.  Yet the trees did not seem to be benefiting from these improvements in soil quality.  Upon evaluating the soil in the tree rows themselves we soon realized that the tree row soil was not improving, only the alleyway soil.  This result is not surprising as the tree rows had no cover crops planted into them and were being maintained bare ground “strips” through herbicides, as is industry standard practice.  When we dug in the alleyway soil we found very few if any tree roots growing into the alleyway.  Since the tree roots were not growing into the alleyway the improvements to the soil there from the cover crops were not contributing to the trees and their crop.  Research led us to Michael Phillips book, The Holistic Orchard, where he described the behavior of tree roots and their interaction with grasses and broadleafs growing near trees.  His conclusion was that the tree roots cannot compete well with the plants growing in the alleyways because the tree is adapted to growing in forest ecosystems, not prairies.  He further describes that the optimal environment for tree roots to grow in is a forest duff.  Phillips uses mulches to create a forest-like duff around his fruit trees.  Upon reading his work we realized that we needed to mulch the cover crops into the tree rows so the trees could realize the benefits of cover cropping.  However he was only doing this work on a small scale using methods not suited for large-scale commercial farming.

Through further research we discovered that “mow and blow” was a technique that some vineyard growers were using to mulch their vineyards.  Mow and blow is pretty simple: a mower cuts the plants in the alleyway and deposits the mulch into the tree row.  We searched for a mower that would allow us to do mow and blow.  Eventually we found the Nobili SDS 210 flail mower with an independent hydraulic system drive and a single-side auger discharge to mow and blow our cover crops.  This unit was affordable and did an excellent job for us.  We purchased a second machine of the same model to allow us to mow and blow all of our orchard acres with these mowers.  To date six area orchardists have purchased the same mower from the local equipment dealer as a result of us demonstrating the mower at field days held as part of this project.  These mowers are durable and parts are readily available for when we have a rare breakdown.

Mow and blow is working very well for us. Large amounts of mulch can be grown in the alleyway and deposited easily into the tree row.  There is not additional operational cost as mowing is already done as a standard orchard practice.  But instead of leaving the mulch in the alleyway, where the project demonstrates that mulch has little to no benefit to the trees, the mulch is deposited in the tree row where it can go to work for the grower.

^{"Mow and Blow":  The Nobili SDS 210 flail mower did an amazing job of mowing down cover crops and depositing valuable mulch into the tree row.}