Sunflower (Helianthus annuus L) production has increased in the central Gre
at Plains, but Little is known regarding how this crop will affect surface
biomass production, various soil quality indicators, and subsequent winter
wheat (Triticum aestivum L.) yields. We hypothesized that sunflower product
ion was reducing soil quality relative to other summer crops because of the
need for tillage to incorporate herbicide, thus reducing surface residue.
Our objectives were to quantify on a Weld silt loam (fine, smectitic, mesic
, Aridic Argiustolls) surface crop residue levels immediately after seeding
wheat, subsequent wheat grain yield, soil organic carbon (SOC), particulat
e organic matter-carbon (POM-C), aggregate stability, and texture in 3- or
4-year rotation. A randomized complete block design with three replications
was used to compare rotations both with and without sunflower. Our data sh
owed 13% lower SOC content and 26% lower POM-C content at the 0- to 5-cm de
pth in rotations with sunflower versus those without. At the 5- to 15- cm d
epths, differences were not significant (P < 0.05). Crop residue by mass wa
s 5 times lower and wheat yields 33% lower in rotations with sunflower, but
no differences were measured for wind erodible aggregates or texture. Till
age to incorporate herbicides for sunflower and low amounts of residue afte
r sunflower in the 3-year rotation contributed to reduced SOC and POM-C, de
creased residue at wheat planting, and reduced wheat yield. If sunflower is
to be included in the central Great Plains, efforts should be made to use
no-till production practices and 4-year rotations with corn.