High Plains Soil & Moisture Conservation Evangelist
Friday, March 1, 1996
filed under: Irrigation/Water Use
Wes Robbins holds up the dry, dark, L-shaped sunflower taproot to illustrate his point: Despite sunflower’s almost-legendary reputation for being able to break up soil hardpans, it is not “Superplant.” Even the hardy sunflower cannot overcome excessively compacted soils. This taproot, which grew down to the hardened layer and was then forced to take a 90-degree turn, serves as a vivid reminder of that reality.
In his inimitable down-home style, Robbins hammers his point regarding the sunflower root’s limitations:
“It doesn’t have a stainless steel tip, and it surely doesn’t have an auger on it.”
The impact of field compaction is just one of many soil and moisture conservation messages which Robbins preaches — and practices — on a daily basis throughout his corner of northeastern Colorado. Based in a small, nondescript office on the eastern edge of Burlington, the 30-year veteran of USDA’s Natural Resources and Conserva-tion Service takes on the tone of an evan-gelist as he lopes through a broad gamut of topics: soil compaction, the use of Nobel blades (undercutters), gypsum blocks, no-till crop production, irrigation efficiency, wheat/fallow rotations and a host of other ingredients in the region’s ag recipe book.
Informative? Indeed. Controversial? Sometimes, you bet. Dull? Never. Robbins doesn’t hold a divinity degree; he doesn’t pass the hat at meetings; and he doesn’t have his own television program (though he has been featured in National Geographic). But there’s no doubt this High Plains “evangelist” firmly believes what he preaches — and numerous farmers in his part of the High Plains have joined Robbins’ congregation of conservationists during the 10-plus years he’s worked out of the Burlington office.
Here’s a quote-worthy “Robbins Sampler” on various subjects related to sunflower production and High Plains agriculture in general.
That’s Not the Issue’
Whether it’s sunflower, corn or wheat, “plants can only grow in soils that are compatible with their root systems,” Robbins begins. “Just because sunflower is a taprooted plant, the thinking is that the taproot will automatically grow through the soil deeper than will a crop like wheat or milo — and then serve as a pipeline for the little roots back to the plant.
“So everyone assumes if you have a taprooted plant, that taproot is developing like a big oak tree.
“But kochia is taprooted; and so is pigweed. Yet they’re also affected by compaction. In fact, when I check a farmer’s field for tilth, I pull up weeds and check their root systems. If the roots are well-developed, straight down, I know he has no compaction problems. If they’re not, he does.”
What about all those producers who say sunflower has definitely helped break up hardpans?
“How many plants have they pulled?” Robbins rhetorically asks. “I’ve spent many hours digging holes in fields with a shovel. I was just in a sunflower field the other day where, though a taproot squeezed through a crack in the soil, the soil was so compacted the plant had limited root development — which resulted in a very small head.
“You have to go out and check your fields. I walk sunflower fields and try to pull up [mature] plants. If I can pull them up, that farmer has a problem.
“Taprooted, non-taprooted. That’s not the issue here. It’s the development of the root system — period. What good does six-foot moisture do you if your plants’ root system goes down just six inches?” (Continued)
Smears & Percolation
Robbins views Nobel blades (under-cutters) as a very useful tool for residue retention — as long as they’re used properly. Yet while blades have been used for many years, that’s not always the case.
“If you look at the shape of a blade plow, you know it’s not built to pull easily, because it stands on its edge,” Robbins observes. “Why? To kill weeds and volunteers, you have to separate their roots from the soil. The guy who designed the Nobel blade wanted turbulence. And the way to get it was through speed and a shallow operating depth: very little soil moved, but a lot of turbulence. When the ground settled back down, the root had been separated and the plant died.
“But as tractors got larger and more powerful, somewhere along the line people started saying, ‘deeper is better.’ Well, if you run it too deep (six to eight inches), you don’t get that weed kill because the roots are still attached to their soil.”
When run too deep and too flat, blade plows can establish a “restrictive layer,” Robbins points out. That layer may not be compacted enough to prevent a sunflower or other crop root from penetrating; but it can form a “smear” which inhibits water infiltration.
“The smear has an effect on percolation because it seals air pores and root holes,” the USDA conservationist states. “When water hits it, the water will run sideways]since it can’t get through the seal. So you can have a thin restrictive layer without having compaction.”
Dealing With Compaction
Picking up a rock-like chunk of eastern Colorado soil, Robbins intones, “This is compaction. Now, do you think a sun-flower taproot will go through that?” The answer is obvious.
“If you have a hangover, the best way to cure it is to quit drinking,” he muses. “If you have compaction, you have to take it out — but you also have to stop putting it back in. Therein lies the problem.”
Robbins has words of caution for conventional-till producers in his region who are considering switching to a no-till system: “If you have compaction, it will take you at least three years to get from where you are to no-till, because your soil is not ready. You can go to bed being a conventional tiller and wake up a no-tiller; but your soil is going to have its say first and last.”
For a producer with compacted soils who is going into ridge-till, Robbins suggests starting with a ripper on 30-inch centers and equipped with row markers. “Rip it in the fall, and then plant right over that rip the next spring. Then you know your root system will have a passageway.” The next step, he advises, is interval ripping every 15 inches.
‘If You Have Moisture, Use It’
High Plains growers still following a two-year rotation of wheat/fallow will not find a sympathetic ear in Wes Robbins. “The wheat/fallow program is a joke,” he declares. “You’re lucky to save 15 percent of annual precipitation” on fallow ground in eastern Colorado.
“There are only two reasons to till: to prepare a seedbed and to control weeds,” Robbins continues, adding that without residue cover, a fallow field is an open invitation for moisture evaporation. “Our drastic changes in temperature from daytime highs to nighttime lows [literally] ‘pumps’ water out of the soil,” he contends. “In the month of August, it can completely drain a four-foot profile.”
“Harvest your moisture every year” is Robbins’ philosophy. He underscores the point by referring to a Burlington area farmer who decided to plant-back a wheat field rather than fallowing it the second year. He harvested 50 bushels the first year and 48 the second. “I said to him, ‘Have you ever made 98-bushel dryland wheat under wheat/fallow?’ ‘No,’ he answered. ‘Well, you just did,’ I said.”
Gyp Blocks: A Field’s Gas Gauge
Robbins has long promoted the use of gypsum blocks as a moisture-measuring tool for both dryland and irrigated fields in his area. A number of growers use them; many still do not, however.
The small plaster-of-paris “corks,” which are buried at one-, two-, three- and four-foot depths (down to six feet in alfalfa ground), absorb and lose water at a rate similar to that of the surrounding soils. The water-use information is fed from the gyp block electrodes through wires extending above the ground. The farmer then connects a portable meter to the wires to get the moisture readings.
While the usefulness of gypsum blocks for irrigators would seem apparent in terms of helping them schedule irrigations, “we also have a lot of gyp blocks in dryland fields,” Robbins relates.
“People say, ‘Why would you put them in dryland? You can’t change anything.’ Well, you can make a decision based on what you have,” he points out, referring to times when he’s advised dryland growers not to plant sunflower — and other times when he’s encouraged them to plant — based on the moisture readings from the gyp blocks. The gyp blocks also can aid growers in making seeding rate or fertilization decisions, Robbins adds.
Slow Down to Reduce Runoff?
Years ago, Robbins started telling area irrigators that if they have water running off from below their sprinklers rather than infiltrating the soil, they should slow down the circle’s speed. The general reaction, Robbins recalls, was something to the effect of, “Who would ever make an idiotic statement like that? If you have runoff, you obviously need to speed up.”
The USDA moisture management specialist persisted, arguing that “when you go fast [while irrigating] every three to five days, the surface gets wet and it seals. If you slow down, the soil has time to ‘crack’ — and these tighter soils have to crack to take water.” If soils are dry, once they start taking water, they’ll continue to do so, Robbins explains. “But once you go off and then come back three or four days later, it won’t take water.”
One farmer who was finally persuaded to slow down his pivot’s speed agreed to do so on one condition: That Robbins agree to come out the next morning and help free what the farmer was certain would be a center pivot that stuck in the wet soil. “He told me he got up about 5:30-6:00 that morning and took off to the field. ‘What did you expect to find?’ I asked. He said, ‘I expected to find the ‘borrow (road) ditch’ full of water and the pivot stuck on all seven towers.’ And I said, ‘What did you find?’ He replied, ‘Nothing. It was puttin’ right along.’ ”
The Bottom Line
“Our whole objective with irrigation is to get the water from the source to the plant root zone with the least amount of waste,” Wes Robbins emphasizes in summing up his moisture management approach to irrigated crops.
With dryland fields, moisture manage-ment is a year-round proposition — the proficiency of which often spells the difference between success and failure in a given crop. Robbins’ goal is to save up as much of Mother Nature’s “free moisture” as possible — but then turn around and invest it in a crop before it’s depleted nonproductively.