Extension Notes: A Dry Spring in Saltgrass County
1Saltgrass County is a farming county on the dry plains of the southwestern United States, where families grow wheat, cotton and sorghum. Strong winds sweep across the county most springs. When the soil is dry and bare, the wind can lift it into a dust storm, a moving wall of dust that can cut how far drivers see on State Highway 9 to a few meters in less than a minute. Crashes involving many cars have happened in these storms. This spring looks dry, so the county's farm extension agent, Ms. Yetunde Halloran, asked Teodora Begay and Callum Nakamura-Reyes, seventh graders in the county farm youth club, to help her plan.
2Wind lifts soil grains only when it blows faster than a certain speed, and that speed depends on the ground. Plants and the stubble left after harvest slow the wind right at the ground, and roots help hold soil in place. Damp soil grains stick to each other. Dust monitors beside fields have recorded the gust speed at which dust starts to blow from different kinds of ground (Table 2).
3Since 2023, the county has paid farmers to plant cover crops, fast-growing plants such as rye that cover a field between one harvest and the next planting. Rows of trees planted along field edges, called windbreaks, also slow the wind, but they take about 10 years to grow tall enough to help.
4In 2020, the state put visibility sensors and electronic signs along a 30 km stretch of Highway 9. When the sensors detect thick dust, the signs lower the speed limit and tell drivers to pull off the road, turn off their lights and take their foot off the brake, so that drivers behind them do not follow their taillights into a crash. A similar 30 km stretch farther west has no sensors (Table 3).
5This year the forecast calls for only about 5 cm of rain from March through May. Many farmers tried to plant cover crops last fall, but the seeds did not sprout in the dry soil, so about 40% of the county's fields are bare this April.