New approaches that emphasize more efficient water use, including cover crops, summer fallow, and wider row spacings, could improve the odds for Texas High Plains producers.
With an annual rainfall of only 18 inches, farming in the Texas High Plains has never been easy. The continuing decline of the Ogalala Aquifer in recent years makes it even harder.
New approaches that emphasize more efficient water use, including cover crops, summer fallow, and wider row spacings, could improve the odds, says Craig Bednarz, director of the Semi-Arid Agricultural Systems Institute, Department of Agricultural Sciences, West Texas A&M, Canyon, Texas.
His main focus is cotton. “We’re trying to figure out how to make cotton more efficient using the water resources we have,” Bednarz says.
His work continues efforts started years ago with Bob Stewart’s Dryland Institute. “When he retired, they renamed it the Semi-Arid Institute to continue with a lot of his work,” Bednarz says.
Rainfed production
He prefers the term “rainfed” over dryland production. “Dryland means no water, and crops can’t grow without water,” he says.
He hopes ongoing research shows better production methods under limited moisture conditions. “We’re trying to improve soil health, so when rainfall comes it infiltrates into the soil; we harvest more of the rainfall. We call that rainfed crop production.
“Now, producers plant cotton into a field that was failed the year before because lack of rainfall prevented a stand or an acceptable.”
A better option, he says, would be to rest that land. He says producers continue to plant in dry conditions because “that’s the way ag policy is written. We need to fallow some ground for 12 months, plant cover crops, improve soil health, and no-till — all those things agronomists were preaching long before I came along. We need to implement those practices, so the next time we have an opportunity to plant, we will have soil moisture.”
Moisture loss
Bednarz says with 18 inches of annual rainfall, fields should have six or seven inches of plant available moisture. That’s not often the case.
“We get a lot more precipitation during a 12-month period than our soils will hold,” he says. “In theory, if you lay out a piece of ground for 12 months, you should have a decent bank of soil moisture to plant into. If we get a little planting moisture and a rainfall or two during the growing season, we have a shot at a 700-, 750-, or 800-pound cotton crop. That’s a lot better than what we’ve been doing here. When we harvest cotton now, we often end up with just a half-bale.”
He says soil sensor research may show as much as 2.75 inches of available soil moisture down to 40 inches, but most of that will be in the top 20 inches of the soil profile.
“That’s just enough moisture to get a crop going; if we don’t have help from Mother Nature, that crop will fail or, at best, will be another 200-pound disappointment.
“We’ve wasted the moisture we had in the profile. On the other hand, by laying that field out, we harvest more rainfall and bring the soil profile closer to the field capacity.”
Evaporation
Evaporation, Bednarz says, is the key. High Plains fields are flat and lose very little moisture to runoff or out the bottom of the profile. “It’s hot and windy,” he says.
Planting a cover and fallowing a field over the summer reduces evaporation loss. “When we get rainfall, the organic matter from the cover reduces moisture loss from evaporation. More infiltrates into the soil. We’re encouraging farmers to implement proven conservation practices.”
Ongoing research at the A&M Bushland station includes planting a cover like rye, which will die as temperatures rise in late spring. “So, it stops using water but still provides ground cover and organic matter.
“We’re collecting data; we measure rainfall and we measure soil moisture. One year, over a period of six or seven months, we got around seven inches of rainfall, but were able to document less than 50% in the soil.
That helps illustrate that when rainfall comes, we lose a lot through soil evaporation. If we improve the soil organic matter, cover it with a cover crop or some kind of crop residue, that should reduce surface evaporation and encourage infiltration down through the profile.”
Best cover crops
Bednarz says cover crop selection is important.
“A few years ago folks promoted a living root cover, which is considered important to soil microbiology interacting with the root system. The problem is that living root systems use water.”
He says one summer cover in use included a multi-species blend with a few legumes, sorghum Sudan, and pearl millets, “forage species that produce a lot of above ground biomass and are drought tolerant. They scavenge the soil for water.
“It didn’t take long to figure out that’s not what we need because that cover uses water we’re trying to preserve for next year’s cash crop. It does a good job covering the ground, and it puts organic matter in the soil, but we need to preserve that moisture.”
He says multi-species blends did not stay around long.
The ideal cover crop, Bednarz says, germinates and emerges and grows off with marginal moisture. It grows slowly and uses little water. It produces a lot of lignin and cellulose that puts organic matter back in the ground. It persists and will not decompose fast.
“I don’t know what that cover is,” he admits, “but if anyone has ideas, let us know.”
Other options
He says cropping options might change and could include grain sorghum, perhaps dividing fields into one-third cotton, one-third grain sorghum, and one-third cover and fallow. “We’re trying to incorporate those options into systems. One system includes a wheat, fallow, cotton, fallow rotation.
“We also planted cereal rye in the fall, a summer cover, and then cotton. That was a living root system we found was not going to work.”
He says rye has potential.
“Rye is not necessarily an income stream but it emerges with very little water. If we get a little precipitation in the wintertime, it will continue to grow. At maturity, it’s pretty resistant to decomposition because there’s lots of lignin cellulose. Rye also is alleopathic, a good choice for winter weed control. Rye cover might help control summer annuals as well.”
He adds that rye dies as temperatures rise. “So, it’s not using water during the growing season. Ideally, you get a bunch of dead rye cover that helps harvest moisture.”
He says growers would not have to terminate the rye, just let it die, do have opportunities in late winter to terminate if desired.
Wider rows
Bednarz says a Cotton Incorporated trip to Australia last year offered new insights into rainfed cotton. “Australian farmers are having water issues as well. Much of their dryland cotton was like we have here, with a twist. They fallow a piece of ground for 12 months, cover it, and plant in wide rows.
“Their standard row width on irrigated ground is 1meter. We saw 2-meter all the way up to 4-meter row spacings. We’ve incorporated some of that in our research. We had 30-inch cotton and 60-inch cotton last year.”
Another trial is continuous conventional-tilled cotton year after year after year. “Basically, that’s what producers have been doing in this part of the world for years. Last year was only the second year we were able to harvest a crop. It made a little over half a bale.
Comparisons coming
“This year we will compare everything,” Bednarz says. “We will plant cotton on everything and hope we’ll get planting moisture, get a stand, and see where we are.”
Research includes large plots, roughly about two acres each in the rainfed systems trial.
Limited available moisture, Bednarz says, demands systems that use every drop of moisture as efficiently as possible. Setting out part of a farm for a year might be a hard sell but a good option to conserve moisture.
“We’re not land limited here,” Bednarz says. “We are water limited.
“Our growers are beginning to accept that they need to make changes to hang on. It’s becoming clearer that what’s happening is not working, and at some point, ag policy will change. Support outside farm country is not what it used to be.”
Source: https://www.farmprogress.com/