Conserving Cropland for the Future
Rich brown soil blankets the hilly farmland of eastern Washington's Palouse region. But during the long, cold winter, drizzling rains - lasting for weeks on end - sweep away that precious soil.
That topsoil has helped make the Palouse famous for its bountiful wheat harvests - and infamous for its severe erosion problems. An average of 10 to 12 tons of soil per acre wash away from Palouse farmland each year. Much moves to the bottom of the sloping fields, eventually working its sediment-clogging way into streams.
For every inch of topsoil lost, wheat yields drop by 2 to 3 bushels per acre.
Researchers and farmers know how to slow this erosion - by changing the way plowing and sowing are done. The practice known as conservation tillage uses tilling and planting implements that leave residues - wheat stubble, barley straw, or pea vines - from last season's crop on the soil surface. These residues cover and protect fields during the cold, rainy months and help retain the topsoil. And conservation tillage, also known as reduced or minimum tillage, typically involves fewer passes over the field with farm implements.
One major problem, however, has stalled widespread use of this tactic - weeds. With less tillage, weeds thrive. Crop residues left on the soil help keep the ground moist and give weed seedlings a better environment in which to emerge and grow. Deep tillage, on the other hand, helps kill weeds by burying their seeds and disrupting their roots.
But farmers may be able to save their soil and their money, as well as keeping weeds at bay, says Frank L. Young, a weed scientist at the ARS Weed Research Unit in Pullman, Washington. Young heads a comprehensive, large-scale integrated pest management project in the Palouse that is now in its sixth and final year.
The project involved seven ARS and five Washington State University and University of Idaho scientists from varied disciplines: soil and weed scientists, economists, engineers, entomologists, and plant pathologists.
They compared two different tillage systems (conventional and conservation), two different crop rotations (2 years of winter wheat followed by spring wheat; and winter wheat, spring barley, and spring peas), and three weed management levels ranging from minimum to maximum.
Each of the 12 different combinations was replicated on four different plots. The plots covered 80 acres and were farmed using field-scale tractors and equipment.
The best systems produced substantially higher profits per acre compared to the others. What's more, the same best-paying methods also meet federal requirements...