Effect of small grain residue and tillage method on the emergence and growth of sunflower (Helianthus annuus L.)

Field studies were conducted to determine the effects of wheat and barley residue and tillage method on the emergence and growth of oilseed sunflower. Additional studies were executed to test the effects of wheat, barley, and rye root and straw residue and the effects of cold water extracts of wheat and barley straw on the germination and growth of sunflowers in controlled environments.

Sunflower planted into tilled and no-tilled three week old wheat residue showed no differences in emergence from those planted into followed plots. Sunflower leaf numbers at four weeks were reduced in wheat residue and in no-till plots. Differences in maturity due to tillage were no longer visible at eight weeks. Sunflower planted into tilled and no-tilled barley straw immediately after barley harvest showed a significant reduction in emergence due to barley residue and to minimum tillage. Significant differences due to treatment for many variables in the barley/sunflower plots could be attributed to low values obtained in no-till fallow treatments. Minimum tillage of barley residue plots reduced sunflower height at six weeks as compared to minimum tilled fallow plots. At eight weeks all minimum tilled plots were more mature than no-tilled plots.

Rye and wheat root and surface straw residue delayed, and barley residue inhibited the emergence of confectionary sunflower in pots. Rye, wheat, and barley residue inhibited the emergence of oilseed sunflower. Wheat and rye residue depressed the growth of oilseed sunflower and wheat residue depressed the growth of confectionary sunflower seedlings grown in pots.

In most cases, the extract of 1:10 dilution of wheat and barley straw reduced sunflower growth. Few significant differences in sunflower growth were seen among the 1:100, 1:1000, or 1:10,000 concentrations of any one small grain variety. Some low concentrations of residue extracts were observed to enhance sunflower growth as compared to control treatments.