Submitted to: Soil Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2006
Publication Date: 7/24/2006
Citation: Busscher, W.J., Novak, J.M., Hunt, P.G., Bauer, P.J. 2006. Increase of soil strength over time in a US southeastern Coastal Plain loamy sand. Soil Science. 171(7):519-526. Interpretive Summary: Because energy costs continue to increase, we reassessed the need to perform expensive soil management practices, such as deep tillage, every year. In 1978, soil management treatments were set up that deeply disrupted a hard soil layer. The deep disruption used a non-inversion tillage technique that broke up a subsurface hard layer without plowing or turning the soil over. Other treatments included surface tillage or not. In 1996, plots were split in half; deep disruption ceased on half of the plots and continued on the other half until 2001 when all deep disruption ceased. By 1999, soil strengths were significantly higher for treatments that had not been deeply disrupted since 1996 than for treatments where deep disruption continued, suggesting that the effects of deep tillage lasted three years. Similarly, by 2004, soil strengths for treatments that had not been deep tilled since 2001 were about the same as those that did not have any deep tillage if those treatments received surface tillage. If treatments received no surface tillage, there was still a difference between deep and no deep tilled treatments, suggesting that avoiding surface tillage can buffer the effects of soil strength build up. Producers might want to review whether or not to deep till on a case-by-case basis based on measured soil strength measurements at the beginning of the season and on how they manage surface tillage.
Technical Abstract: With rising energy costs, fuel-consumptive soil management practices, such as deep tillage, need to be reassessed to determine whether they need to be performed every year or not. Between 1978 and 1996, conservation (non-disked) and conventional (disked) tillage treatments had been annually deep tilled with non-inversion subsoiling to break up a subsurface layer that has high soil strength and was associated with an E horizon. After 1996, treatments were split with half being deep tilled until 2001 after which no treatments were deep tilled, although surface tillage continued. By 1999, treatments in which tillage ceased in 1996 were significantly higher in soil strength than treatments that had been deep tilled suggesting that the effects of deep tillage lasted three years. By 2004, conventional treatments in which tillage ceased in 2001 had reconsolidated to the point that they were not different from those conventional treatments where tillage had ceased in 1996. However, conservation tillage treatments were still significantly different, suggesting that conservation tillage can help buffer the effects of reconsolidation. Even though reconsolidation might not be complete, soils with incomplete reconsolidation can be hard enough to reduce production. On the other hand, previously tilled soils still show the effects of deep tillage even after they reconsolidate to the point that they are not statistically different from non-deep-tilled treatments.