EFFECT OF SUBSOILING AND SUBSEQUENT TILLAGE ON SOIL BULK-DENSITY, SOIL-MOISTURE, AND CORN YIELD

Many producers use subsoilers periodically to alleviate suspected comp action caused by traffic from tillage, planting, and harvesting equipm ent, In the fall of 1988 a study was initiated in the upper Midwest re gion of the USA near Morris, Minnesota to study the effects of a one-t ime subsoiling and its interaction with four subsequent primary tillag e systems (fall moldboard plowing, fall chisel plowing, spring disking , and no-tilling) on soil compaction, soil moisture, penetrometer resi stance, and corn (Zea mays L,) growth and grain yield, The experiment was established on a Hamerly clay loam (Aeric Calciaquoll)-Aastad clay loam (Pzchic Udic Haploboroll) complex, Subsoiling was performed in t he fall of 1988 and the study was cropped to continuous corn from 1989 to 1991 on a site that had been farmed many years by normal 6-row, 76 -cm row width equipment, Results show that subsoiling had very little effect on plant growth and no effect on grain yield over three croppin g seasons following the subsoiling operation, Subsoiling had significa nt effects on soil bulk density and volumetric soil moisture content i n 1989, but by 1990-1991 these effects were not significant. Volumetri c soil moisture content generally increased in relation to soil bulk d ensity increases. Tillage impacted surface residue accumulation, but d id not affect soil bulk density, volumetric soil moisture, or grain yi eld, Results from this study indicate that subsoiling soils does not n ecessarily result in better yields or better soil moisture availabilit y, particularly if compaction problem are not evident.