Organic no-till and mulching systems are a huge time saver on our farm. They’ve allowed us to increase production while reducing labor on our six acres of vegetable production. This spring was our easiest year yet even though an illness in April made it difficult to leave the house. I owe the time savings to the roller crimper.
The roller crimper is a heavy metal drum with dull blades that rolls over cover crops, lying them flat and crimping the stems to help kill them. The cover crop remains as a weed suppressing and water conserving mulch and transplants or seeds are planted through the mulch without tillage. However, for crimping to work, the cover crop must be mature, limiting the technique to several weeks during the spring. In addition, weeds are only suppressed for six weeks preventing no-till from working with long season crops like eggplant and peppers.
I’ve invented several techniques to make organic no-till more widely adaptable for farms, overcoming some of the hurdles of organic no-till along the way. In the first technique, I plant cover crops on tractor-pulled raised beds and terminate them with a traditional roller crimper. The raised beds appear to promote early maturity and better cover crop and subsequent cash crop growth in our loamy soils. The second technique delays cereal rye maturity by up to two weeks, extending the planting timeframe for no-till. I use a manure spreader in a third technique to add leaf mulch to the crimped cover crop, extending the weed suppression timeframe from six weeks to six months. And, a fourth technique crimps rye cover crops up to two months earlier by adding leaves on top to prevent regrowth. By combining all of these techniques, I can grow nearly all our crops using organic no-till or mulching systems.
Weed-free cover crops
The first step to a successful no-till program is growing a weed-free, vigorous cover crop. To do this, I plant all my cover crops into a raised stale seedbed. First, I make the raised beds using a tractor drawn bed shaper. If fertility is needed, I add the fertilizer prior to making the raised beds or grow a leguminous cover crop prior to making the raised beds. Next, to make a stale seedbed, I wait for at least a half an inch of rainfall or irrigate the field thoroughly. The rain promotes weed seed growth on the raised beds.
Once the beds have dried enough to cultivate, I bring the tractor cultivation equipment over the raised beds to kill the weeds. The cultivation toolbar is equipped with sweeps and side wings for the furrows, crescent hoes for the sides of the raised beds and S-tines for the tops. The idea is to cultivate as shallowly as possible to kill any weeds without bringing up more weed seeds from deeper in the soil. Stale seedbedding once works well, but twice is best.
I perform the last stale seedbedding when the moisture in the soil is just dry enough to perform the cultivation. I then wait between 4-12 hours to ensure the weeds have died from cultivation then plant into moisture. I apply the seeds with a spinner spreader or bag seeder and then re-bed with the bed shaper to incorporate the seeds.
I read about “planting into moisture,” but never understood how powerful this technique is when performed after stale seedbedding. Stale seedbedding dries out the surface and leaves the soil loose and unable to give the seed-to-soil contact needed for germination. Cover crop seed planted into the moisture beneath the dry soil surface germinates, while the weed seeds on the surface sit idle from the dry stale seedbed. The cover crop seeds then start growing before the next rain occurs, getting a huge head start on the weed seeds. Once the cover crop starts growing, the plants release weed fighting allelopathic chemicals preventing weed seed germination. The chemicals combined with stale seedbedding create a completely weed free cover crop.
Cover crop seed selection, planting density and timing also play critical factors. For winter cover crops terminated in spring, I plant a cereal rye variety called Abruzzi at 150 pounds per acre. I plant the rye six months before our first fall frost date. Planting early gets the rye going before fall cool season weeds start growth. Some of the summer weeds may germinate, but the first frost will kill them before they set seed. Planting earlier or later creates problems with either the warm or cool season weed groups. If nitrogen is needed, I’ve added crimson clover. However, clover breaks down quickly, possibly decreasing weed suppression when used as a mulch. I now add nitrogen to rye before planting by growing a cowpea cover crop. For summer cover crops to be crimped, I use Japanese millet at 30 pounds per acre combined with sunn hemp at 50 pounds per acre and focus on stale seedbedding preferably twice before planting. I crimp the summer cover crop mix according to millet maturity.
Extending weed suppression
Since crimped cover crops only suppress weeds for six weeks, they work best with fast growing crops like winter squash, summer squash and cucumbers. Longer-season crops like tomatoes, eggplant, peppers, sweet potatoes, cantaloupes and watermelons grow for such a long period of time that weeds eventually intrude, creating a mess.
To solve this problem, I add a layer of leaves to the crimped mulch to extend the weed suppression. The leaves are delivered free from the adjacent city in trucks. The trucks vacuum, shred and compile the leaves into specialized dumping bins holding over ten cubic yards. Once stockpiled, our 125-bushel PTO driven manure spreader then applies two inches of leaves over ¼ acre in two hours. Two inches added to crimped rye gives around six months of weed control depending on cover crop density. Adjust down depending on the crop planted into the mulch, but even one inch will drastically improve weed control and help fill in weak areas in the cover cropping system.
To extend the weed suppression in no-till with mulch, I first crimp the cover crop then let it dry out for a few days to become carbonaceous and resistant to decay. Leaves are then applied before or after planting transplants. When applied on top of plants, I unbury the plants by hand after application. Also, some plants such as peppers don’t like mulch up against their stems, so I carefully pull it back. Be prepared for mulch to delay plant maturity by about one week.
Manure spreader mulcher
Manure spreaders apply mulch quickly and evenly over the soil making them the perfect mulching machines. However, our ABI manure spreader is slightly wider than our tractor. When we make raised beds this means that the tires on the manure spreader don’t follow the tractor furrows but travel along the edge of the adjacent raised beds. Depending on planting arrangement, raised beds may need wider spacing to accommodate the manure spreader.
Applying leaves on top of crimped cover crops means a small amount of leaves can make a big difference. However, applying leaves on bare soil in larger amounts works well for weed suppression and has many applications. With garlic, I plant three rows per raised bed into bare soil. Just prior to the garlic emerging, I add four inches of leaves to smother the weeds. The garlic pushes through the leaves and the weeds never have a chance.
This saves us around 40 hours of weeding in our one-fourth acre of garlic. With potatoes, leaves applied prior to sprouting will prevent weeds and conserve moisture, but also delay potato emergence and maturity. For early emergence and maturity in potatoes, apply leaves after the first cultivation or hilling. Storage onions are the final crop I’ve used with leaf mulch alone. I apply a layer of mulch to beds prepared in the fall. The mulch is applied to a four-inch depth and remains fallow without a cover crop through the winter. The leaf mulch keeps the weeds at bay until I’m ready to plant the onions in late winter or early spring. I then plant the sets directly into the leaf mulch or just below the soil because both methods seem to work well and the onions stay weed free until harvest in June.
With early season plantings of summer squash, cucumbers and cantaloupe, soil warmth is important. Growing early crops on bare soil for the first few weeks encourages earliness from increased warmth. Delaying leaf mulch application until after the first cultivation takes advantage of bare soil warmth while also providing the benefits of mulch.
One year, it was too wet to get into the field and cultivate the crops. However, a break in the weather dried the field out enough to drive the manure spreader over the plants. I applied the leaf mulch with the manure spreader while the weeds were one inch or less, smothering them. My crops were just tall enough to stay above the layer of leaves and pushed through with a little help. The leaf application saved us from a weedy mess the wet spring would have caused.
Early crimping with mulch
Many farming inventions and lessons are happy accidents. This one happened when I crimped a rye and crimson clover cover crop about two weeks earlier than I should have. The cover crop wasn’t mature enough and popped back up, smothering the tomatoes I’d planted. However, I applied leaves to part of the crimped area – and to my surprise the rye stayed down and died and the crimson clover pushed through the leaves and continued to flourish. I realized with this accidental experiment that applying leaves allows early termination of some cover crops.
To better understand the potential of the technique, I performed two replicated trials using four different mulch depths and two different age classes of mulch on top of rye crimped at three different stages of early maturity. The younger leaves were collected in fall and the older leaves were collected from the previous year’s fall. I applied the leaves one, two, four and six inches deep. My observations indicate that the older leaves worked better at preventing rye regrowth than the younger leaves. I noticed that the wind blew the younger leaves around possibly opening up areas to light. Older leaves congealed together, creating a light-blocking mat. Although the one- and two-inch depth mulch did not prevent ryegrass regrowth, four and six inches of mulch did.
Immature rye is more succulent than mature rye. Because of this, the weight of the crimper must be reduced as much as possible to prevent the crimper blades from cutting through the rye. Once the grass is cut, it easily pokes up through the mulch and continues to grow. I emptied all the water from the crimper to reduce the weight before use. Also, early crimping probably changes nutrient dynamics with decomposition. The succulent nature of the young rye likely promotes a more favorable release of nitrogen for subsequent crops, compared to more mature rye.
I saw little difference in the timing of the early crimped rye. The first crimping occurred Feb. 21 when the rye was twenty inches high, just prior to the boot forming (stage 9) the second occurred on March 6 as it was just starting to head (stage 10-10.1) and the third on March 20 when the rye was heading (stage 10.5). The earliest treatment had the most regrowth. However, the crimper weight was too heavy during this treatment and was adjusted for the later treatments.
I also performed a single treatment with two replications on a cover crop of mustard crimped on March 6 just prior to the mustard flowering. With the mustard treatment even the one-inch mulch depth was successful. The control plot that was crimped without adding mulch to the mustard stayed down but weeds quickly invaded.
Planting into mulch
We recently purchased a mechanical transplanter with a no-till attachment to help facilitate planting into the mulched systems, but I haven’t tested it out yet. Previously, transplanting into mulch proved more time consuming in comparison to bare soil, but still saved time in the long run with less tractor work and weeding. Since rye dries the soil out, I pre-irrigate with a drip line if needed to moisten the soil prior to transplanting. I then use trowels or a bulb planter to remove soil in the planting hole for the transplants. The bulb planter is a specialized item from A.M. Leonard that has the ability to push the plug of soil out without turning the bulb planter upside down to save time. Ideally the planter is the same diameter as the transplant plug.
Planting into the early terminated rye with mulch on top proved more difficult than I expected. When the leaf mulch is moved out of the way to plant into the ground, rye is exposed to sunlight and is difficult to cover back up with the leaves. Once exposed, the rye continues to grow and competes with the adjacent plant. Waiting one to two weeks after applying the leaf mulch on top of the rye ensures that the rye is shaded long enough to kill it.
Alternatively, I planted directly into the leaf mulch on top of the rye and this worked the best. The leaves were shredded which helped retain moisture and the older leaves worked better than the younger leaves. Irrigating twice was enough to keep the plants alive during the wet spring we had while conducting the trials. A dedicated drip line for the plants would have alleviated any drought stress I observed.
Cold damage was the biggest issue with crops planted into the early crimped rye with leaf mulch placed on top. The mulch prevented the soil from warming and the kale and broccoli I planted into the system were damaged even though they are cold hardy crops. I didn’t harden the transplants off before transplanting because this hasn’t been an issue when planting into bare soil, but should definitely be done with early crimped systems. The transplants placed directly into the soil under the mulch had more cold damage than the transplants placed into the mulch on top of the soil. Cold air probably settled into the depressions in the mulch made when planting into the ground. In addition, the dark colored older leaves applied as a mulch showed less cold damage on transplants than the newer leaves probably because the darker color and denser mulch absorbed more solar energy.
Pests and early crimping
Crops planted in the early spring are notoriously susceptible to cabbage maggots, a tiny fly that lays its eggs on the soil near plants. The fly larvae decimate the root system and girdle the stems, leading to a dead plant after a few days. The problem is worse when planting into a freshly tilled cover crop. The freshly decomposing organic matter attracts the flies and the larvae move from dead cover crops to transplants. To combat the problem, I only plant early spring crops into a field of winter-killed cowpeas. The cowpeas decompose through the winter and in early spring no fresh organic matter is left to attract and feed cabbage maggots.
With the early crimped rye covered by leaf mulch, I expected cabbage maggots to thrive in the fresh decomposing rye below the leaves, consuming any transplants in the system. To my surprise, I had no cabbage maggot damage in the treatments. Early one morning while observing the trials, I noticed swarms of fungus gnats hovering above the leaf mulch on top of the rye. As the fungus gnats landed on the mulch to lay eggs, a pack of predatory mites would emerge from the mulch and consume the eggs immediately. I’m assuming the predatory mites played a role in controlling the cabbage maggot problem, allowing a massive amount of fresh rye organic matter to be applied in the early spring.
Another happy accident occurred when I conducted the trials with leaf mulch covering the rye. Every treatment in my plots had a control that was crimped but not covered with leaf mulch. Rye in these areas regrew from the early crimping operation. However, I noticed the rye matured later in these areas. Late maturing rye is useful for late-planted crops in no-till systems. Since crimped rye only prevents weeds for six weeks, it’s important to plant soon after crimping. If you crimp when the rye is mature, then wait two weeks to plant, only four weeks of weed control are left.
With late-planted crops, four weeks of weed control may not be enough to get the cash crops established. Crimping rye to delay maturity provides a solution, but it must be done at the correct time. If done too late, some of the rye will stay down and decompose leaving thin areas in the mulching system. More research needs to be done in this area. However, from my observations it appears that crimping when the rye was two feet in height at the pre-heading stage allows maximum regrowth while still delaying maturity by around two weeks.
Within our intensive cover cropping systems, I’ve seen the organic matter content of the soil increase one-half percent every year and now reads close to six percent. I strive to use no-till techniques as much as possible and follow cash crops with cover crops by avoiding double and triple cropping systems. Now that we’re adding mulch to the crimped cover crop systems, I expect organic matter contents to climb much faster. I’ve read that for every one percent increase in organic matter, the soil can hold up to one inch more water. More water stored in the soil means more opportunities to dry farm or reduce irrigation.
In the potato and garlic systems described earlier, I only irrigate at the critical crop development stages. When planting winter squash into crimped cover crops, irrigating a few times after transplanting helps plants establish enough to dry farm during a normal rain year on the East Coast. All other crops are irrigated with drip tape placed on top of the crimped cover crop. Pre-irrigating with the drip tape makes planting by hand much easier if the soil is dry. Transplants are then easily watered in and automatically irrigated with the drip system.
Cover crops rarely provide all the fertility to grow the vegetable crops unless legumes are added. Therefore, with rye only cover crops crimped as a mulch, I add fertilizer to the system. I do this prior to planting or I band the fertilizer beside the plants after transplanting. I’ve successfully used blood meal and cotton seed meal with surface applied techniques. However, during a dry year, the fertilizer may not wash down into the soil to feed the plants and I’ve observed deficiencies during drought.
I believe fertigation systems injecting the fertilizer through the drip tape would be ideal, but I’ve yet to adopt the practice. Another consideration with fertility is the increase in organic matter content over time. Calculations indicate mineralization of the organic matter in our soils is releasing 75 pounds of nitrogen a year. While not all is released during a short cropping period, the organic matter is still delivering a substantial amount of fertility to the crops.
The trials I conducted were not analyzed in a scientific way, just through observations taken during my free time. More research is needed to verify my observations and expand the potential for the techniques. Analyzing wood chip and compost mulch in addition to leaf mulch on top of a wide range of cover crops at different depths and at different times for early crimping and extended weed control would help advance and verify the techniques even more. With all the new organic no-till techniques, I see a future where 75 percent of our crops are grown using no-till techniques – saving us time and money while improving the soil.
Shawn Jadrnicek is the author of The Bio-Integrated Farm: A Revolutionary Permaculture-Based System Using Greenhouses, Ponds, Compost Piles, Aquaponics, Chickens, and More, available from Growing for Market. He has nourished his interest in sustainability through work as an organic farmer, nursery grower, extension agent, arborist, and landscaper, and now as manager of Wild Hope Farm in Chester, South Carolina.