Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2005
Publication Date: 1/17/2006
Citation: Busscher, W.J., Bauer, P.J., Frederick, J.R. 2006. Deep tillage management for high strength southeastern USA Coastal Plain soils. Soil & Tillage Research. 85:178-185.
Interpretive Summary: In the southeastern US, crop yields can be limited by high soil strength. High strength can be broken up by tillage shanks that shatter the soil without inverting it; that is, without traditional plowing. Between 1996 and 2001, we compared surface and deep tillage while growing wheat and soybean in different crop and soil management systems. Wheat yields improved with lower soil strength related to deep tillage. Soybean yields also improved; but the improvement was not a result of lower soil strength as much as it was a result of the total management system which combined deep tillage and narrow rows. Wheat yields improved when the wheat-soybean double crop was rotated with corn; but soybean yields did not change. Experimental plots were large enough, 500 ft long, so that they had different soil types at each end. Soil types had different soil strengths at different depths, as a result of tillage; yet their yields did not differ. Crop production can be improved by reduction in soil strength but combining lower strength with other management criteria, such as narrow rows or rotations (depending on the crop), can have a greater effect on production.
Technical Abstract: Southeastern USA production systems are limited by soils that have high strengths and low water holding capacities. Production systems that were rotated or deep tilled before every crop were compared with less intensive management. Production systems included double-crop wheat (Triticum aestivum L.) and soybean (Glycine max L. Merr.) drilled in 19-cm-row widths grown in 15-m wide, 150-m long plots with varying hardpan depths. Treatments included surface tillage (disked or none), deep tillage (paratilled or none), another deep tillage rotated with maize (Zea mays L.) and winter fallow, and conventional disked/deep tillage with an in-row subsoiler where soybean was planted in conventional 76-cm-wide rows. Cone indices were measured near the end of each plot (120 m apart) to assess soil strength differences among soil types and among treatments. Cone indices were higher for non-deep tilled treatments vs. deep tilled treatments and in wheel tracks vs. non-wheel tracks. They were also higher for soils with shallower Bt horizons. Cone indices of subsoiled treatments were not significantly different from paratilled treatments. Rainfall was erratic throughout the 5-year experiment with long dry periods and with annual totals ranging from 520 to 1110 mm annually. Wheat yields were greater for deep-tilled soils (subsoiled and paratilled) than for non-deep-tilled soils. Soybean yields were greater for paratilled than for subsoiled or non-deep-tilled treatments partly as a result of the more complete disruption of the paratill and partly because paratilled treatments were managed with narrow rows. Yields were not significantly different among soils despite the fact that they had different cone indices. Tillage was a more dominant factor than soil type. For wheat, lower cone indices from tillage led to higher yields. For soybean, management of uniform loosening from deep tillage and narrow rows led to higher yields.