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Fall Harrowing of Spring Barley Stubble Before Summer Fallow

Objective

Compare the effects of fall harrowing versus not harrowing spring barley stubble on population of weeds and volunteer barley in the spring and surface residue cover after seeding winter wheat at the end of the summer fallow season.

Location: Colfax, WA
Annual precipitation: 17 inches
Soil: Athena silt loam
Previous crop: Spring barley planted under minimum tillage
Rotation: Winter wheat, spring barley, fallow

Treatments

Tine harrowing of standing spring barley stubble before fall rains in early October 1993
Undisturbed standing barley stubble over winter

Comments

Each treatment was replicated 4 times. Plot width was 28 feet. Plot lengths were 1000 feet for two replication and 800 feet for two replications. Population counts of weeds and volunteer barley were made with 9 ft square hoops on March 28, 1994, just before the initial summer fallow tillage operation. Four measurements were taken per plot.

All plots were disked with the rest of the field on April 11, and then managed as minimum tillage summer fallow using a field cultivator/harrow, shank-fertilizer application and rodweeder. Because of limited seed zone soil water after the dry, hot summer, winter wheat was seeded shallow in dry soil in late October with a double disk drill. Percent surface residue measurements were made with the line transect method at six locations per plot on November 22, 1994.

Data

Populations (plants/sq yd) of weeds and volunteer barley on 28 March 94

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Fall harrow	183	397	430	332	335a
No harrow	142	119	320	135	179a
LSD (5%)					164
CV					28%

Percent surface residue on 22 Nov 94 after winter wheat seeding on fallow

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Fall harrow	23	28	23	27	25.3a
No harrow	29	26	27	31	28.3a
LSD (5%)					5.5
CV					9.2%

Conclusion

Although there was a trend towards higher spring populations of weeds and volunteer and lower surface residue levels with fall harrowing, the differences were not statistically significant. The dry conditions during the fall and winter minimized weed and volunteer germination and establishment. Dry overwinter conditions also probably reduced rates of decomposition of the barley residue, again limiting potential differences between the treatments.

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Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU