Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2002
Publication Date: 10/1/2002
Citation: BUSSCHER, W.J., BAUER, P.J., FREDERICK, J.R. RECOMPACTION OF A COASTAL LOAMY SAND AFTER DEEP TILLAGE AS A FUNCTION OF SUBSEQUENT CUMULATIVE RAINFALL. SOIL & TILLAGE RESEARCH. 2002. V. 68. P. 49-57.
Interpretive Summary: In two previous studies, we quantified decreases in corn, wheat, and soybean yield as soil strength increased in southeastern US coastal plains. In this study, we quantified the rate at which strength built up in these soils over the years. Rainfall (or time since tillage which was highly correlated with rainfall) accounted for 67 to 91% of the increase in compaction over the six years of the experiment. We measured soil strength of a sandy coastal soil in experimental plots that were deep tilled twice a year or less to examine recompaction. Soil strengths were measured from seven days to six years after tillage. Recompaction was slower than previously measured because we controlled traffic lanes and because we used a deep tillage tool that almost completely loosened the soil to about 14 inches without inverting the soil (without conventional plowing that turns the soil). Recompaction was temporarily greater near the surface because that was where rain first affected the soil. Knowledge of recompaction rates can be combined with information on yield reductions from compacted soils and predictions of rainfall to help producers make management decisions on frequency of deep tillage which can be expensive in terms of labor, fuel costs, and large equipment requirements.
Technical Abstract: For many Coastal Plain soils in the southeastern USA, high soil strength within subsurface horizons requires that deep tillage be performed to provide a suitable rooting environment. We measured cone indices in a fine loamy Acrisol near Florence, South Carolina, for treatments that were deep tilled twice a year or less to examine recompaction. Cone indices were measured from seven days to about six years after tillage. Measurements were made at the point of maximum disruption by a bent-leg subsoiler (Paratill) which tilled between 0.35-m to 0.40-m depths. Regressions of cone indices with rainfall explained 67 to 91% of the recompaction and indicated that recompaction was still taking place six years after tillage, at the end of the experiment. Recompaction was slower than expected probably because of controlled traffic or excessive disruption by the paratill. Recompaction was also temporarily greater for the 0.1-m to 0.2-m depths when compared to the 0.25-m to 0.35-m depths. Though recompaction was slow, tillage would still be necessary annually or seasonally because yield would be reduced by incomplete recompaction that increased soil strength after a year or less.