Steel in the Field: A Farmer’s Guide to Weed Management Tools

	Horticultural Crops: The Farmers Intensive Controls Keep California Beds Clean Paul Muller Full Betty Farm Guinda, California 40 acres vegetables clean tillage sandy clay-loam soils soil compaction tendency high certified organic 18 to 30 inches annual precipitation irrigated 60-inch beds fresh market, wholesale and retail sweet corn, vine crops, tomatoes, beans, broccoli, lettuces, greens, onions, garlic Weed management highlights Strategies: crop rotation... pre-irrigation and stale seedbed cultivation... flaming... early season mechanical cultivation... cover crops... balanced soil fertility Tools: precision cultivator, flexible tooling... rolling cultivator... custom toolbar flamer... hand-held flamer... rotary harrow (PTO-powered)... mechanical guidance... offset tractors with belly-mount option Intensive use of an array of adapted tools has greatly lowered weed pressure over the past 10 years on the Full Belly Farm. Paul Muller handles much of the field and shop work that puts the right steel in the field at the right time. He’s brought morning-glory and Johnsongrass under control without herbicides by combining intensive tool use with crop management that improves soil biological health and soil structure, and balances nutrients at optimum levels. His early season weed control centers on soil preparation, well-timed irrigation and moisture management. Typically, Muller spreads about 8 tons of compost per acre before disking then subsoiling. The compost goes on at an early stage in field preparation or when cover crops are incorporated. He lets cover crop residue decompose for about three weeks after disking before the next tillage pass. That time period varies with moisture, amount of cover residue, how finely the residue is chopped up during incorporation and how thoroughly the residue is incorporated with soil. Alternatively, Muller has planted corn immediately after thorough incorporation and had good results. “But don’t try to plant in between, or the seed is just something else to be composted in the intense biological activity of the soil/residue mix,” he says. His three-row bed shaper uses shanks and shovels to loosen soil so that large V-shaper wings with metal forming panels can throw up soil to make beds 44 inches wide and 8 inches high between 16-inch wide furrows. He’s careful to create straight, parallel beds and rows. This makes precision mechanical weed control as easy—and as fast—as possible. As soon as beds are formed, Muller sprinkle irrigates to stimulate germination of surface weed seeds and breakdown of the cover crop residue. He turns to his weed management tools as soon as weeds emerge and moisture is suitable—certainly before they reach a half inch tall and have consumed precious irrigated moisture. He lightly tills the beds with a Lely Roterra rotary harrow. (See Chambers,) He keeps the PTO driven, spinning tines in the top 3 inches of the soil where they dislocate all weeds and leave many on the surface. Muller favors the tool over a rotary tiller because it’s faster and he feels it maintains better soil structure in his fields. He reports the Roterra also preserves moisture by creating a loose soil mulch, and its forming shovels re-shape beds nicely. He turns dry conditions to his advantage by “planting to moisture” all his direct-seeded crops. By pushing back dry soil and creating a row furrow, he places crops into a deeper moisture layer. They thrive while weed seeds have to wait for the next precipitation to germinate. (This is a version of the “lister planting” popularized in the Great Plains.) The practice works about 90 percent of the time, Muller reports, allowing for the once-in-a-decade spring rain that puts moisture everywhere at the wrong time. Metal guidance wheels hug the sides of the bed to firmly align his toolbar-mounted planter. A V-shaped row opener creates a firmed soil layer at its point that aligns seeds, draws moisture to them from below through capillary action and provides the ideal location for the seed radicle to penetrate lower for more moisture. Disk openers don’t provide him these moisture benefits. Small-seeded crops such as lettuce, brassicas and carrots germinate uniformly and ahead of many weeds thanks to this strategy, Muller reports. “It’s always worth the extra wait to pre-irrigate then clean cultivate,” he says. “It may delay planting by a week, but it saves dollars on weeding.” For slow-growing crops such as carrots, Muller stymies weed competition with a custom toolbar flamer. He attaches three self-vaporizing burners (rated at 350,000 to 750,000 BTUs per hour), centering them 12 inches apart, each one over a three row band of planted but non-emerged carrots. He controls the regulator and shut-off for the toolbar-mounted LP tank from the tractor seat. Groundspeed is 3 to 5 mph. Properly used in a timely fashion, the flamer controls 80 percent of in-row broadleaf weeds, but has little effect on grasses. When irrigation or rain causes soil to crust before plants emerge, Muller runs crustbreakers to enable seedlings to develop. These tools are widely used in California to cover whole bed tops preemerge, or to run between rows ahead of weed-control tooling. Crustbreakers come in many styles but are commonly made of light angle iron pieces welded into rolling baskets. Preemerge, they run ahead of top knives, which are finely sharpened pieces of straight beveled blade stock about 4 inches wide. The knives may be 6 inches to 5 feet wide and run perpendicular to the bed. Attached to toolbars by straight shanks, they run quite shallow and almost flat, with a slight rise that lets soil easily flow up and over their top surfaces. They can be fashioned in farm shops from road grader steel, with a little grinder work to set a sharp edge. Muller employs a single-burner, wand-type hand flamer for spot weeding when it’s too wet for the tractor to do toolbar flaming. He uses a Red Devil burner on a 4-foot pipe. A 5-gallon LP cylinder mounted on a hard-frame backpack fuels the system. He can cover 1 to 2 acres per hour, depending on weed pressure. Crops jump ahead of weeds when the pre-plant tillage, flaming and dry surface soil steps combine as intended. “When this system works, all weed management tasks go easier for the entire season,” Muller finds. One indicator of his consistent early-season success is the limited demand for hand-weeding beyond what’s done during hand-thinning: “Half of the time we don’t even need it.” For emerging crops, he outfits a 15-foot toolbar with five tool-mounting crossbars. Holding the Alloway vegetable cultivator in place are the same bed-hugging guidance wheels he used on the planter. For each row unit, he clamps on a pair of 12-inch cutaway disks that run 0.5 inches to 4 inches from the row; flat, low-profile vegetable knives that slice weeds but do not throw much soil; and tent shields over the rows that protect tender plants from moving soil. To cultivate the outside edges of the bed, he uses a pair of curved banana knives per side. One runs deep, one shallow. Shovels with strong vertical soil-thrusting action clean out the furrow and re-shape the beds. Basket rollers on the back of the unit lightly pack the soil on bed tops to curb moisture loss. At first pass, when the disks are set only 2 inches apart straddling the rows, he travels 1.5 to 2 mph. At second cultivation he pulls the disks further apart to accommodate crop growth and runs 3 to 4 mph. To save the time involved in re-tooling then readjusting a cultivator toolbar between crops, Muller has a selection of five cultivator toolbars outfitted for different planting arrangements: precision units for single rows or three rows on beds; Lilliston implements for 30-inch rows and single bedded rows; and one to combine cultivating and listing, the making of furrows that precede bed shaping. Minor adjustment as crops develop take relatively little time once row-width and depth settings are fixed. “If you keep only one tool at a time active, you tend to rob pieces from here and there,” he found. “Then you end up looking for those parts when you should be out in the field. With five toolbars ready to go when conditions are just right, our operations are much more timely. Things just work a lot better.” He uses a Lilliston rolling cultivator on sweet corn once it reaches 3 inches tall. He sets the five-wheel spider gangs parallel to the row at first pass to work soil and destroy weeds. At this setting, the ground driven, curved arms lift and lightly toss soil but do not move it into the row. At second cultivation, corn stalks are sturdy enough to tolerate some soil flowing against them to smother in-row weeds. Traveling at about 5 mph, he adjusts the horizontal angle and sideways pitch (allowed by the round mounting standards) to move just the right amount of soil into the row area at the base of the crop plants. (See rolling cultivator illustration) Because of its several areas of adjustment, setting up a rolling cultivator is especially important to its effective operation. It takes time and experience to learn the skill, but when done well results in excellent control for many users with free-flowing soils. “Once I’m set up, I don’t have a problem,” says Muller, who encounters virtually no rocks or residue in his fields. He uses it on other upright crops such as cauliflower, garlic and onions and Romanesco broccoli, all of which he plants in 30-inch rows. He finds that this unusually wide spacing for onions and garlic is justified with the rolling cultivator. He can run it quickly through the rows several times per season, taking out weeds between the rows and smothering in-row weeds, as well. “This outfit works really well,” Muller says. “Many commercial conventional growers use them, and they could get along without herbicides if they wanted to. They use cultivation as insurance, when it could be their main protection.” He believes mechanical weed control will continue to grow in popularity as farmers learn more about organic cropping systems and new crop/tool systems develop. He’s glad to be in a place with an abundance of available appropriate technology. “I live in an area with lots of good tools around that you can buy cheaply,” he says. “If you make the effort, you can learn how these tools worked in an era when people knew how to use them.” Next farmer All Farmer Profiles