May 1997
The trials suggested below are given to help develop new information about weed control options. Most of these trials can be done by any grower interested in experimenting with the idea. Results of most of these trials also can be quantified by the grower, such as changes in yields or quality of the harvest. To develop a more detailed picture of what is happening in the field, it is recommended that the grower notify local researchers and the IPM coordinator to inform them of upcoming field trials. In this way, useful trial information may be communicated to others and/or refined and investigated further. Some trials are appropriate for a number of Refuge-grown crops, and others are only appropriate for one crop.
1. Ridge tillage for potatoes and sugarbeets. Every time a field is tilled, new weed seeds are brought near the surface to germinate. No-tilling or strip-tilling potatoes or sugarbeets into grain may reduce or eliminate this problem.
North Dakota-Minnesota teams of researchers and farmers conducted on-farm studies over a period of 5 years that concluded ridge till in sugarbeets reduced soil erosion by increasing crop residue approximately 70 percent over conventional tillage, provided better soil moisture during seed germination, reduced fuel needs for tillage by up to 42 percent, reduced labor needs by up to 18 percent, and reduced populations of several key weeds significantly (e.g., over 50 percent reduction in redroot pigweed.(19)(20)
In one 3-year study, yields achieved in 2 of the 3 years (including recoverable sugars) were statistically equal between conventional and ridge till systems. In the other year, ridge till outperformed conventional tillage by 1.14 tons/acre yield, 0.49 percent increase in sugar, 507 lbs. of recoverable sugar per acre, 12 lbs. of recoverable sugar per ton, and a net profit of $74 per acre.(20)
In a separate 2-year study, ridge till provided better residue and soil moisture, provided better yields (i.e., tonnage, percent recoverable sugars, nitrate grade), reduced the number of tillage operations for seedbed preparation and weeding, reduced weed populations, reduced soil erosion, and increased profits per acre.(20)
Research[1] in Willamette Valley (21) showed that snap beans planted into a fall-planted barley cover crop eliminated the need for spring tillage and reduced early season weed emergence by 87 percent. Flailing the barley cover increased crop emergence and yield, but also increased weed emergence.
What is ridge till? Dickey(22) describes ridge till as a one-pass, tillage and planting method. Seed is planted in 4 to 6 inch high ridges formed during cultivation of the previous crop (in the fall or late summer). Two cultivations are used for ridge building, one to loosen soil and the other to create the ridge. Ten percent of leased- land acreage can be fall tilled to implement an IPM practice.
At spring planting, sweeps or other row cleaning devices mounted in front of the planters, shave off the top 1 to 2 inches of ridges and push clods and residue between rows. This results in a cleanly tilled seedbed with strips of residue between the rows that reduce erosion.
Ridges dry out and warm up faster in spring compared to non-ridged sites. Most often a band of herbicide is applied during planting and crop cultivation is used for weed control between the rows.
Since planting is done into a ridge that may have loose soil on top and more compact soil on the sides, achieving a uniform planting depth may be difficult for growers new to the system. Some producers chop residue or perform shallow tillage to smooth ridge tops and reduce equipment malfunctions caused by excessive crop residue. Proper ridge shape and annual maintenance are the keys to making the system work. Care must be taken not to damage or destroy the ridges by wheel traffic.
Equipment necessary for ridge till could include rotary tillers, mulch shredders, tandem disks or harrows, furrowing wings, and sweeps.
2. Strip tillage for potatoes and sugarbeets. Strip till is similar to ridge till except that just before planting, rather than shaving off the top of the ridge, a 7-inch-wide band is tilled there. Beds or ridges are 24 inches apart. After tilling, beets are planted using a conventional planter. Bill Iversen, a beet grower in northeastern Montana, pioneered this method.(23) His off crop is grain, which he treats as a row crop. He claims reduced erosion and ground preparation costs.
3. Flame weeding. Flaming the seedbed after weed emergence but prior to crop emergence has potential for reducing herbicide use in potatoes, sugarbeets, and onions. Pre-plant, pre-emergent and postemergent applications have been successfully applied in various crops.
Preplant flaming has been referred to as the stale seedbed technique. This method is similar to using Roundup, only the weeds are seared after emergence with a flame weeder instead of with an herbicide. Flaming could replace pre-emergent applications of Roundup, except where perennial weeds are a problem.
For preplant flaming, seedbed tillage is completed and weed seeds (mostly in the upper 2 inches of soil) are allowed to sprout. Assuming adequate moisture and a minimum soil temperature of 50 degrees F (to a depth of 2 inches.), weed germination should occur within 2 weeks. A fine-to-slightly compacted seedbed will germinate a much larger number of weeds. The weeds are then "seared" with a flamer, preferably when the population is most susceptible: between the first and sixth true leaf stages. The crop should be sown as soon as possible, and with minimal soil disturbance to avoid bringing new seed to the surface. For the same reason, subsequent cultivations should be shallow (less than 2 inches deep).(24) Pre-emergent flaming may also be done after seeding and prior to crop emergence.
Searing the weed is much more successful than charring. Excessive burning of the weeds often stimulates the roots and encourages regrowth in addition to using more fuel. Flaming has generally proven most successful on young, broadleaved weeds. It is reportedly less successful on grasses, as the seedlings develop a protective sheath around the growing tip when they are about 1 inch tall.(25)(26)(27)(28)
Pre-emergent flaming may also be done after seeding and prior to crop emergence. Careful monitoring is required to make sure the flaming is done early enough to avoid damaging emerging seedlings.
Research in Europe on post emergent flame weeding in onions indicates that it has potential, but is rather exacting. Though onions become fairly heat resistant when they reach the four-leaf stage, they do remain sensitive to excess heat. Uniform seedbed preparation, consistent ground speed, and minimal wind during post emergent flaming are critical to successful use of this method in onions.(26)(27)(29)
See Useful Contacts and Resources for a list cultivation equipment manufactures and suppliers.
4. Trials with various cultivation tools. There are a variety of innovative cultivation tools that can be used during the season to control weeds such as rolling cultivators, basket weeders, steerage hoes, spring-toothed weeders, spring-hoe weeders and finger weeders. Trials to see how well some of these cultivators work in leased-land crops should be considered.
Rolling cultivators are versatile, ground-driven cultivation systems. Cultivating tines are mounted on toolbars and are either overlapped so they will cultivate wide areas, or are set to weed between rows. The tines can be positioned to either move soil toward or away from the row.
The Buddingh "basket weeder" is a high-speed cultivation device designed for very early cultivation. Since the weeder does not throw soil onto the row, it can be used right after planting without burying emerging plants.
Steerage hoes, developed in Europe, are mounted behind the tractor onto the three-point hitch. While one operator drives the tractor, another sits in back and steers the hoe. This enables cultivation to be done very close to the crop. Spring-toothed weeders have narrow, flexible, curved tines that are mounted to a toolbar. The tines vibrate as they are pulled along the soil surface, and they break up the crust and control small weeds that are still in the white-tipped stage.
Bezzerides Brothers have engineered implements that can precision-cultivate between rows as well as between plants in the row. Their "spring hoe weeders" travel just below the soil surface along either side of the crop. The vibrating action of the spring hoes disturbs the soil just enough to uproot weed seedlings within the row without harming the crop plants. "Spyder tines" are used in conjunction with the spring hoes and replace the discs on a traditional cultivator. Unlike conventional discs, spyder tines do not leave a hard band of soil next to the crop row (where weed seedlings can survive), nor do they cut crop roots.
The Buddingh "finger weeder" uses flexible teeth and rolling tines to kick out seedling weeds from between plants within the row without disturbing the more deeply rooted crop species. This weeder provides excellent control for young crops (up to 4 inches in height) and should be adaptable to use in a number of row crops.
See Useful Contacts and Resources for a list of cultivation equipment manufactures and suppliers.
5. Flooding. Flooding acts to control weeds primarily through oxygen deprivation. It is known to be highly effective in controlling established perennial weeds, such as quackgrass. It has also shown some promise in suppressing certain annual weeds by reducing weed seed populations. Among the species that flooding is expected to suppress are common lambsquarter, redroot pigweed, Kochia, hairy nightshade, and wild oats.(30) Flooding is a weed control practice that might benefit all crops grown on leased lands.
6. Test covercrops as weed management tools. Cover crops and green manures also can be effective tools to manage weeds. Studies in Washington State found that fall-seeded Jupiter rapeseed grown as a green manure crop decreased weed biomass from 50 to 96 percent. Combining the rapeseed cover crop with one cultivation may eliminate the need for herbicide applications in many situations, while maintaining potato yields.(31)
[1] This same study showed that planting snap beans into a fall-planted barley cover reduced the incidence of white mold on snap beans to a level comparable to the conventional plot treated with Ronilan. Planting snap beans in flailed (threshed) barley was more effective in decreasing white mold compared to planting in unflailed barley
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