Dryland Crops: The Farmers
Oregon's Deep Soils, Sloping Fields Reward Gentle, Careful Tool Use
- 1,400 acres wheat
- mulch tillage
- deep silt-loam soils with enough clay to crust
- 75 percent of land with slopes 2 to 8 percent; balance steeper
- 10 to 22 inches precipitation, depending on field location
- heat-fallow two-year sequence, with a rotating quarter of the land cropped annually in barley, canola, mustard or cannery peas
Weed management highlights
Strategies: Minimum tillage... careful match of weed tools with soil conditions... hand roguing
Tools: spring-tooth harrow... spike-tooth harrow... rod weeder... chisel plow... tandem disk.... rod-tine-sweep combination
In Clint Reeder's part of northern central Oregon, the Blue Mountains have a lot to do with how farmers farm and control weeds.
'You lose a half-inch of rainfall per year for every mile you are away from the mountains,' he explains. 'In close, you can raise annual crops. My area is a wheat-fallow rotation, because we have to wait for a year between crops for enough moisture to plant.'
This is the Columbia Plateau, a vast region of rolling hills and variable soils in central Oregon and Washington. Because he has deep topsoil that retains water well, Reeder can manage residue and tillage to produce a good wheat crop (85-95 bushels per acre) on the alternate production years. Shallower soils in the region lose as much moisture as they gain each year, requiring different techniques.
'I'm committed to relying as heavily as we can on mechanical tillage, then using the fewest, safest herbicides we can to maintain production,' says Reeder. A no-herbicide wheat crop isn't in his plan, but he knows its limits in his two-year, wheat-fallow system. In '95 he raised 1,000 acres of herbicide-free wheat. 'First time. Last time,' is the way he sums up the experience.
He had burned residue in '93 to control disease on those same acres. The fire cleaned up broadleaves and cheatgrass, but seemed to open a niche for tarweed fiddleneck (Amsinckia lycopsoides), a tough-stemmed, bristly annual. It invaded in patches where there had been annual crops or an area of freezeout within the previous 15 years. His yield was 17 bushels per acre lower where the tarweed was bad, compared with 95 bushels per acre where weeds were under control.
His other weed challengers are various thistles that germinate year-round and the cool-season pests of cheatgrass, goatgrass and wild mustard. He's battling field bindweed in one 160-acre field that has enough moisture for continuous annual cropping. He rotates in cannery peas, canola or culinary mustard, seeking to use differences in soil cover and root structure to weaken the bindweed patches.
The fallow-season schedule fluctuates with moisture conditions, but field work follows in a general progression after harvest in July or August. Reeder controls weeds in the stubble by using a tandem disk or Field Cultivator in the fall. When he notes random escaped weeds that could cause a problem, he uses a sharp hand hoe.
He Chisel Plows with wide sweeps as soon as he can in February or March. The pass controls winter-annual weeds while maintaining 80 to 90 percent of the residue, and opens the soil to receive the spring rains.
The combination of residue levels, soil condition, and surface moisture determines which tools he uses before and after applying fertilizer in April or May. Options include a field cultivator, rod weeder, springtooth harrow or a combination tool (Culta-Weeder, below) that is heavier but able to combine more treatments with one pass. Reeder's rule is to do tillage as shallowly, as infrequently and with as little soil impact as possible - while still allowing moisture to soak in.
He drills in wheat from mid-September through the third week of October as his varied soils reach the right moisture conditions. He usually applies a herbicide treatment in some parts of his fields about March. Rate and material depends on which weeds hit an economic threshold.
He makes the most of the flexibility of the three-way action of the Calkins Culta-Weeder. The trailer-mounted, secondary tillage tool works well for him in many fallow situations. It displaces, uproots, and pulls out weeds, then leaves them exposed to dry.
The frame resembles the structure and strength of a chisel plow. His model has three 12-foot sections, with the two outer wings folding up for transport. Two ranks of C-shanks with sweeps open soil of the weed root zone. A third toolbar is the mounting point for rod weeder sections and flex-tine harrow sections.
'The Culta-Weeder loosens up the soil, kills weeds and levels soil for planting,' says Reeder. Considering its multiple roles and mobility, Reeder feels the $23,800 tool pays its way. He's careful to keep it off moist soil, though, to avoid wheeltrack compaction that can channel water and allow soil erosion. Later in the season, soil is firm enough and the rainfall light enough that the tool's action poses little erosion risk, even on his sloping ground.
He can tailor the tool's soil impact by ground speed, adjusting any one of the three components, by disengaging one of the components, or by dropping the hitch height to change the depth alignment. Other adjustments include
Shanks. Reeder usually wants just enough tillage to improve water infiltration. He runs 6-inch duckfoot sweeps on 12-inch centers, leaving half the surface undisturbed. Depth of the sweeps helps to keep the depth of the rod weeder consistent. If soil is loose and dry, he may flip up the shanks for no sweep action.
Rod weeder. This 1-inch square rod spanning each 12-foot section is the main weed-killing part of the tool. A ground-drive mechanism spins the rod so that the leading edge is moving upward, ripping up weeds and flipping them onto the soil surface. Reeder drops the depth as low as 2.5 inches when weeds are tall (8 inches), but usually runs it at about 1 inch.
Flex tines. 'The tines give you a compromise between soil structure and weed kill,' Reeder explains. 'A flatter angle is less aggressive, just right for small weeds when soil isn't crusted. As you stand the tines up, you cover wheel tracks better and kill bigger weeds, but sometimes beat up too much on the soil.'
When the Culta-Weeder's combinations aren't right or its weight (9,000 lbs.) is too heavy for conditions, Reeder selects a simpler and lighter tool.
Reeder's lowest impact tools are a springtooth harrow or simple rod weeder. Both tools are good at plucking weeds - the springtooth up to 3 inches, the rod weeder up to 8 inches - and leaving them on top to dry out.
The classic springteeth are made of flat spring steel used in an upside-down C-shape. They are fastened to a light toolbar at the front. The pointed tips vibrate in all directions just below the surface in loosened soil but accommodate only minimal residue without bunching it up. Their low draft enables Reeder to pull a 60-foot springtooth with the same 235-hp tractor needed to pull the 36-foot Culta Weeder. He often uses the harrow on soft, recently plowed soil.
When he needs only weed control in a field with good residue, his standard rod weeder is the tool of choice. It's light and runs quickly through fallow fields. Reeder values and carefully manages the tool's second benefit - the thin compaction layer formed at its bottom surface by the turning motion.
'Creating a moisture barrier with the rod pan is critical in this dry country,' Reeder has found. He avoids setting the layer too early in spring where it could prevent rainfall from penetrating, thus causing erosion.
Whenever possible he runs the rod weeder about 2.5 inches deep after the final rain of early summer. This pass takes out weeds and stops moisture from escaping. The layer stops capillary action of moisture moving from subsoil to the surface. Moisture stays below the line, and the 'dust mulch' of loose soil and residue prevents evaporation. He continues to use the rod weeder or harrow at a shallower level throughout the summer fallow season until fall planting.
Reeder grapples with tradeoffs from higher residue in his fields. He wants to keep protecting soil and smothering weeds, but high-moisture years bring bigger wheat stalks and more straw. He likes the yield, but has to deal with greater disease potential from fungi that thrive in moist, dead vegetation.
Further, bringing more precipitation into the soil increases leaching of toxic soluble salts from deep subsoils into groundwater. This phenomenon has caused pH to shoot up to 9.4 in one low area of his farm. He accepts these challenges as part of learning a more sustainable system on his side of the Blue Mountains.