From The Fort Morgan Times (Jeff Rice):
That’s the first instruction from Mike Petersen, a retired soil scientist and agronomist. Petersen was a presenter at Wednesday’s South Platte River Salinity Workshop presented by the Centennial, Morgan and Sedgwick County Conservation Districts.
Petersen manages the Orthman Research Farm near Lexington, Neb., and consults with growers regarding strip-till system technology, fertilizer, crop development, root development, and water management.
The agronomist addressed misconceptions about salinity in the South Platte Valley during Wednesday’s program. Chief among those misconceptions is that a good rainfall or snowmelt, along with cover crops and no-till practices will solve the problem…
Phil Brink of Colorado Cattleman’s Ag Water Network led off with an overview of the issue, which he said has been followed in the Colorado River basin for several years. Brink said salinity levels below Hoover Dam are about 723 milligrams per liter, or about what is in the South Platte just below Denver…
By the time the river gets to Sterling, however, that salinity has skyrocketed to 1,275 mg/l, almost twice as salty as the Denver reaches.
While much of the problem stems from treated wastewater discharged by municipalities and industries upstream, agriculture is compounding the problem. The re-use of return flow water from upstream irrigation is concentrating salts from cropland and leaching it into the river, where it’s diverted or pumped onto crops and the cycle starts over.
There are things that can be done to mitigate the damage, however. Petersen said no-till cultivation and leaving residue on the soil surface is the first step farmers need to take. Better water management, crop rotations and alternative crops are other methods producers can use to minimize salinity in the soil and, thus, in return flow to the river.
“That’s the good news, but it’s going to cost everyone something,” Petersen said. “And there’s just no option. Change is mandatory.”