|Camp, Carl - ARS-RETIRED|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 2005
Publication Date: December 1, 2006
Citation: Busscher, W.J., Bauer, P.J., Camp, C.R. 2006. Cotton management of a compacted subsurface microirrigated Coastal Plain soil of the southeastern U.S. Soil & Tillage Research. 91(1-2):157-163. Interpretive Summary: In 1991, perforated microirrigation tubing was buried in research plots at the bottom of a Coastal Plain soil's plow layer and just above its root-restricting hard layer to efficiently provide water to plant roots. Since then, while several experiments were performed on the plots, soil above and below the tubing hardened more than expected reducing yields and the soil could not be loosened using conventional tillage because of the buried tubing. An experiment was initiated to loosen soil and increase cotton yields using various types of tillage without disrupting the foot-deep tubing. Shallow tillage, such as disking or chiseling, was ineffective because it could not loosen soil close enough to the tubing to be effective without risking damage. Deep tillage (non-inversion deep loosening) had mixed results. If tubes were buried in alternate mid rows, in-row deep tillage was effective in increasing yield. If tubes were buried under the rows, deep tillage between the rows did not increase yield; however, these yields were mid range: no better than the treatment with no deep tillage and no worse than the treatment with in-row deep tillage. For these soils, irrigation tubes buried under every other mid row allow for in-row deep tillage that can improve yield; and, as seen in previous work, this tube location is just as productive as and less expensive to install than burying tubes under every row.
Technical Abstract: A loamy sand acrisol (Aquic Hapludult) that had been microirrigated for six years became so severely compacted that it had root limiting values of soil cone index in the Ap horizon and genetic hardpan below it. Deep and surface tillage systems were evaluated for their ability to alleviate compaction. Deep tillage included subsoiling or none. Each deep tillage treatment was surface tilled by disking, chiseling, or not tilling. Subsoiling was located in row or between rows to avoid microirrigation tubes (laterals) that were buried under every other mid-row or every row. Cotton (Gossypium hirsutum) was planted in 0.96-m wide rows. Irrigation improved yield from 485 kg/ha to 1022 kg/ha because both 2001 and 2002 were dry years. Tillage loosened the soil by an average of 0.5 to 1.3 MPa; but even for tilled treatments, compacted zones remained outside tilled areas. Subsoiling improved yield by 131 kg/ha when performed in row where laterals were placed in the mid rows; but it did not improve yield when it was performed in mid rows. For subsurface irrigation management in these soils, the treatment with laterals buried under every other mid row was able to accommodate in-row subsoiling which improved yield; and this treatment was just as productive as and less expensive to install than burying laterals under every row.