Sunflower Stalks Trap More Winter Snow, Soil

WASHINGTON -- Mar 30/99 -- When fierce 30-mile-per-hour-plus winds swept across some research fields in Akron, Colo., this winter, they hit a 2-1/2 foot high "wall" of sunflower stalks left after last fall's harvest. That wall kept soil from blowing away.

Had it not been an unusually dry winter in Akron, that wind would have carried snow--and that wall would have trapped 3 to 10 times more snow than would normally accumulate.

Agronomist David C. Nielsen with the Agricultural Research Service in Akron found that 2-1/2 feet is the height needed to trap enough snow to add 3 to 9 more inches of soil water. This makes up for soil water used by the sunflower crop and makes sunflowers a worthwhile alternative to wheat in the arid Great Plains.

There, average precipitation is only 16.5 inches a year. Rain is so scarce that most farmers traditionally have dared plant a crop only every other year, leaving the ground bare or fallow for a year to save up enough soil water for a crop.

But through research such as Nielsen's, farmers increasingly plant crops two or three years in a row--and make more cash. And since rains don't fall to suit farmers' timetables, planting an additional crop like sunflowers gives them a better chance to get the timing right for at least one crop.

Leaving stalks or other plant residues on the ground after harvest is what makes the annual crops possible. The residue provides a soil mulch that reduces evaporation, stores water for the next crop and fights wind erosion, according to Nielsen, with ARS' Central Great Plains Research Station.

The ARS scientists have found that sunflower yields are best when the crop is rotated in every fourth year. The usual rotation is wheat-millet-sunflower-fallow. This gives time for sunflower diseases and other pests to die out.