STEEP - Gypsum and Subsoiling to Improve Soil Conditions

To test effectiveness of the soil amendment gypsum and subsoiling practice in improving moisture infiltration, surface structure, soil profile moisture, soil quality parameters, and crop production for sodic soil conditions.

Location: Clarkston, WA - Peola Road
Annual precipitation: 12 inches
Rotation: Winter wheat-summer fallow

Check (no treatment)
Gypsum application @ 1 ton/ac
Subsoiling
Subsoiling and gypsum application

The field was summer fallowed in 1994. That fall Marcus took over the lease from operator Steve Vickery and seeded winter wheat. Seedbed conditions were extremely dry with poor emergence and plant stand. The plots and field were then reseeded to hard red spring wheat. Plots were harvested on 9/14/95.

**Spring wheat**, bu/ac
Treatment	Rep 1	Rep 2	Rep3	Rep 4	Average
Check	35.9	26.8	32.5		31.7a
Gypsum	32.9	30.6	27.8	26.6	29.5a
Subsoil	33.3	30.3	24.5	24.1	28.1a
Sypsum & subsoil	33.1	32.2	27.5	25.6	29.6a
LSD(5)					4.1
CV					8.6%

No significant yield differences resulted from the treatments.

Conclusion

Soil test results showed an increase in exchangeable sodium percentages in the 2nd foot for the subsoil, subsoil & gypsum, and gypsum treatments. The largest increase occurring in the subsoil plot. The highest total moisture was found in the subsoil treatment but was not significant. The gypsum additive had created some visual improvements in the soil=s surface structure; however improved profile moisture was not verified by soil tests. Sodium was being released by the treatments but not moving from rooting zone (1-2') in the sampling.

Gypsum and Subsoiling to Improve Soil Conditions and Crop Yield Potential for Asotin County Sodic Soils

Gypsum and Subsoiling to Improve Soil Conditions and Crop Yield Potential for Asotin County Sodic Soils