Farming Adaptations Needed To Combat Climate Change To Impact Crop Yields In 2050

  • Sorghum is a staple food crop in West African countries whose crop yields already suffer from long droughts and unpredictable rainfall.
  • Using heat-tolerant varieties of sorghum as a new management practice shows the most potential as an adaptation for maintaining crop yield as global warming raises the temperatures in West Africa.
  • This study’s unique framework compares how West African sorghum crop yields will fare in the higher temperatures and higher CO2 of the future–if specific farming management practices or technologies are adopted and if they are not adopted.
As the globe continues to spin toward a future with higher temperatures, crop yields will likely decrease if farmers do not adapt to new management or technology practices. Establishing new strategies is particularly difficult for sorghum farmers in West Africa where seed varieties and fertilizer are scarce, while drought and unpredictable rainfall are prevalent. Using more heat-resistant sorghum varieties may yield the most benefits, research shows.
“Climate change will impact both natural and agricultural ecosystems on the planet. The difference is that farmers can do things to adapt to the changing climate, and hopefully alleviate the impacts on their crops,” says Kaiyu Guan, an environmental scientist at the University of Illinois.
Guan and his colleagues conducted a research project modeling practices farmers could adopt, weighing them against climate change scenarios.
“We started with a long list of adaptation options, but we finally narrowed it down to five that we believe are more feasible options for the future and for the sorghum farmers in West Africa,” Guan says.
The team uses 30 years of historical precipitation and temperature data–from 1961 to 1990–as well as eight different scenarios to project future climate changes from 2031 to 2060. Drawing from a new schematic of crop yield response under historical/current and future climate developed by the co-author David Lobell from Stanford University, they were able to determine the impact on crop yield from five management practices.
A summary of the findings show:
  • Late sowing, or choosing a safer time to plant, did not show much benefit.
  • Increasing seed density and using more fertilizer results in higher crop yield, with or without climate change.
  • Changing the length of thermal time required for sorghum to grow results in a reduction in crop yield.
  • Collecting rainfall to use during a dry spell will only marginally benefit crop yield with or without climate change.
  • Using sorghum varieties that are more resilient to heat stress during the flowering period proves to have the most potential for greater crop yield with higher temperatures in the future.
Guan says this research confirms what previous studies have concluded. “If farmers don’t do anything about climate change in West Africa, there will be a severe impact–a net loss in crop yield. We have to do something. We also discovered that most of the approaches are not as effective as what we expected.”
But, it’s the novel way the team uses well-validated crop models to address the specific research question for which Guan sees the most value in assessing the potential impacts of the five farm management strategies.
“Our goal is to quantify the impact of a specific proposed adaptation option to determine how effective each adaptation is,” Guan explains. “The new framework allows us to make those calculations so that the five adaptations in the eight climate change scenarios can be assessed against what the crop yield would be if no adaptations were initiated by farmers.”
Guan adds that this study provides detailed data for sorghum grown in the region of West Africa and a suggestion that the use of more heat-tolerant varieties of sorghum is the adaptation that will be most helpful. He believes this information will be useful to government agencies as they decide where to invest research dollars for adapting to climate change.
“People have said for a long time that some adaptation should be possible. But identifying which specific investments are most likely to help, and by how much, is still a pressing need, especially given the billions of dollars now being earmarked for adaptation,” says Lobell.
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Tips for Sorghum Planting Success

1. Plant the right hybrid.

Choose the hybrids that best fits your geography and environment, advises Scott Staggenborg, director of technical services for the sorghum genetics firm Chromatin. While yield is the top goal, be cognizant that the hybrid you selected last fall may not be the best fit for this spring’s climactic conditions. You may have your hybrids picked out already, but in most cases, “it isn’t sold until it is in the ground,” Staggenborg says.

Crop maturity lessens the farther north you go, so producers in northern Nebraska and South Dakota will need earlier-maturing hybrids, particularly if planting runs later. Also, keep in mind the precipitation outlook. “Farmers in west Texas, for example, plant medium to medium-early hybrids because when it gets dry in the summer, it is better to have the crop finished earlier,” Staggenborg says.

Seed supplies are good, so producers still have time to select hybrids. Use regional, multiple-year yield data as a guide for hybrids that fit in your area. Another trait producers should look at is the ability of a hybrid to withstand lodging.  A stay-green or standability performance factor is one indicator that the crop will not fall prior to harvest.

Adding a seed treatment such as Cruiser to sorghum seed is a good idea, particularly when planting into no-till, he adds.

2. Use a pre-emerge herbicide.

Curtis Thompson, weed management specialist at Kansas State University, says a pre-emerge herbicide program is a must in controlling herbicide-resistant weeds, problem broadleaves and – the bane of all sorghum growers – grassy weeds.

“There are enough tools in a sorghum producer’s toolbox to do an effective job in weed control,” Thompson says. The first rule, he adds, is to not plant sorghum where shattercane or johnsongrass is a known problem.

A pre- and post-emerge program using the Callisto mesotrione products – either Lexar or Lumax – may be expensive, but is effective at providing season-long control of many annual grasses and broadleaf weeds. Lawrence, Nebraska farmer John Dolnicek, says a split application combined with glyphosate a week to 10 days prior to planting, combined with a second application of the same prior to emergence, helps fields “start clean and stay clean.”

For in-season control of broadleaves, Thompson says a post-emerge application of Huskie – a premix of pyrasulfotole and bromoxynil – can be made after the crop reaches the three-leaf stage and before it is 30-inches tall. Huskie needs to have a half-pound of atrazine added to the tankmix. However, do not apply to ground previously treated with Lumax or Lexar, Thompson warns.

3. Use enough fertilizer.

Grain sorghum is oft-considered a low-maintenance crop, but it may require more nitrogen than you think.

“We often hear from farmers who thought their sorghum should yield better, but they didn’t put on enough nitrogen,” Staggenborg says.

Ideally, producers should base fertilizer recommendations on soil test data. Failing that, research at Kansas State University shows that sorghum requires 1.6 pounds of nitrogen per bushel of expected yield, assuming 2.0% organic matter. By the time nitrogen credits are accounted for, a rule of thumb is apply one pound of nitrogen per bushel of expected yield.

If planting into no-till, a few gallons of starter fertilizer at planting will give the crop a boost in cool, damp soils. Starter is not as important in conventional tillage systems, he adds.

Keep in mind the crop following sorghum, too. Soil scientist Ray Ward of Ward Laboratories in Kearney, Nebraska, says sorghum that yields 120 bushels per acre takes from the soil 102 pounds of nitrogen, 42 pounds of phosphorous, 30 pounds of potash, 14 pounds of sulfur and one pound of zinc.

4. Seed it correctly.

Today’s planters are extremely accurate. But many farmers still use grain drills or air seeders to plant sorghum, and they need to know how much seed to apply per acre.

“It becomes a challenge to get the correct seeding rate because farmers are using volumetric measure, and not every hybrid contains the same number of seeds per pound,” Staggenborg says. “Read the tag, and make sure you get the correct number of seeds per acre.”

Staggenborg has the following seeding recommendations based on yield objectives:

  • Low Yield, Dryland: 30,000 seeds per acre
  • Medium to High Yield, Dryland: 70,000 sees per acre (caveat: shorter-season environments may want more seeds per acre to prevent tillering).
  • High Yield, Irrigated: 90,000 seeds per acre.

He recommends planting at least 1.5-inches deep, as shallow planting results in uneven stands. Be sure to account for residue when setting seeding equipment; a mat of residue can result in shallower planting than expected.

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