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Chiseling versus Plowing of Summer Fallow to Reduce Water Erosion

Neil and Phil Heitstuman
with Frank Gariglio, NRCS-Lewiston; Larry Smith, Nez Perce Co. Cooperative Extension;
and Roger Veseth, WSU/UI

Objective

Compare the effects of spring chiseling versus moldboard plowing in summer fallow after winter wheat on water erosion during spring/summer thunderstorms and overwinter under winter wheat, and on yield of the following winter wheat crop.

Location: Culdesac, ID
Annual precipitation: 22 inches
Landscape: 15-20% slope with south aspect at an elevation of about 1,900 feet
Previous crop: 43 bu/ac winter wheat (about 2 normal yield due to drought)
Crop rotation: Winter wheat-fallow

Treatments (Spring primary tillage only)

1. Moldboard plow
2. Straight-shank chisel

Comments

Plots are 180 feet long and arranged end-to-end on the contour at a width of 140 feet beginning at the top of the field. Primary tillage was performed on contour in early June. Subsequent operations on all plots included: field cultivation shortly after the primary tillage, three rod weedings over the summer, fall shank fertilizing, rod weeding and seeding with double disc drills in October. Initial residue level averaged 1,770 lb/ac.

The study was designed to evaluate the perception of some producers in the area that spring-chiseled summer fallow is more prone to erosion under spring/summer thunderstorms than with spring moldboard plowing. These types of high intensity rainstorms are common in the lower elevation zones of the county. There is some indication that this low elevation cropping area is also less subject to overwinter erosion associated with runoff on frozen soils, a problem common to much of the Inland Northwest cropping region. Spring chiseling of fallow is included in one of the "approved tillage systems" for conservation compliance in this production area of the county.

Data

No soil erosion was found on either treatment during the fallow period, although heavy spring/early summer rainstorms occurred in the study area.

Surface Residue (lb/ac) in November 1995 in established winter wheat

Treatment	Rep 1	Rep 2	Rep 3	Rep 4	Average
Plow	63	16	0	31	30a
Chisel	47	31	63	47	47a
LSD (5%)					51
CV					61%

Conclusions

The study is not complete. Rill erosion differences will be monitored over the winter of 1995-96. Winter wheat yield measurements are also planned. Additional data will be needed to determine if changes in "Approved Tillage Systems" are warranted in this cropping region.

Precipitation throughout the spring and summer of the fallow period was significantly above normal in the study area. Although no erosion was measured, there was ample "opportunity" with heavy spring and early summer rainstorms. The low surface residue level on all treatments was largely attributed to the initial low residue production due to drought conditions for the 1994 winter wheat crop and to an accelerated rate of residue decomposition in the fallow period due to moist soil conditions.

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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