|Hanna, Mark - IOWA STATE UNIVERSITY|
|Jensen, James - IOWA STATE UNIVERSITY|
Submitted to: Journal of Production Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 28, 1999
Publication Date: N/A
Interpretive Summary: What should be done to silty clay loam soils that were flooded or appear to have been compacted by intensive rainfall? To answer this question, an on-farm study was conducted in southeastern Iowa on silty clay loam soils that received excessive rainfall and were partially flooded during 1993 when rainfall throughout much of the Midwest was more than 20 inches above average. Soil physical properties and crop yield were measured and costs associated with various tillage treatments were used to compute simple budgets for no-till, chisel plow, or subsoiling treatments. Soil physical properties were altered, but crop yields were not changed. Based on our assumptions, the net return for corn was $54/acre less with subsoiling and $42/acre less with chisel plowing than using no-tillage or the least amount of tillage needed to prepare a seedbed and ensure proper operation of our cooperator's planters. For soybean, moderate tillage (chisel plowing) returned $20/acre less than the shallow or no-tillage treatment. Our results indicate that money spent on subsoiling and chisel plowing was essentially wasted on a perceived problem of rain- or flood-induced soil compaction. Based on these results, we and our Extension Service cooperators recommend that farmers who are managing silty clay loam soils such as those upon which this study was conducted, should use no-tillage practices after a year of intensive and extensive rainfall and subsequent flooding rather than investing in subsoiling or other forms of deep or moderately-deep tillage.
Technical Abstract: Excessive rainfall and subsequent flooding of many Midwestern agricultural fields in 1993 resulted in numerous questions regarding the amount of tillage needed to prepare fields for crop production in 1994. Five locations, flooded between June and August of 1993, were selected for on-farm comparisons of shallow, moderate, and deep tillage. Bulk density, soil-water content, penetration resistance, and yield of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were measured, and net return was computed. Pre-plant bulk density within the upper 12 inches averaged 1.27, 1.26, and 1.22 g cm**-3 for no-till, chisel, and subsoiled treatments, respectively. Penetration resistance averaged 130, 120, and 97 psi for the no-till, chisel, and subsoil treatments, respectively (LSD(0.05) = 7), and showed highly significant differences as depth increased from 0.5 to 12 inches. Pre-plant and post-harvest soil-water content was 1 and 3% greater in no-till than in tilled areas. Post-harvest bulk density was not significantly different, but penetration resistance averaged 378, 341, 330, and 283 psi (LSD(0.05) = 19) for no-till, chisel, field-cultivated, and subsoiled areas, respectively. Although increased tillage intensity had some significant effects on soil physical properties, crop yield was not increased. Therefore, we conclude that economically farmers should seriously consider using no-till rather than deep tillage following intensive rainfall and flooding events similar to those occurring in 1993.