Author
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UNGER, P - 6209-05-15 |
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Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/23/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Soil surface conditions improve when organic matter concentration (OMC) and water-stable aggregation (WSA) increase, but surface variability may influence results obtained at sampling. In this study, effects of cultural operations on OMC and WSA of soil used for ridge-tillage sorghum [Sorghum bicolor (L.) Moench] production were determined. Pullman soil (Torrertic Paleustoll) was sampled in furrows and on ridge tops and sides before and after planting, after rebuilding ridges, and after harvest in 1992. Tillage [conventional (CT) and ridge [with early (RT-E) or late (RT-L) stalk shredding]], position, and sampling time affected OMC and WSA. Mean OMC (g kg**-1) was 19.1 with CT, 20.7 with RT-E, and 21.4 with RT-L; 19.5 (mean) on ridge top and side positions and 22.7 in traffic and 20.6 in non- traffic furrows; and 22.0 before planting, 18.8 after planting, 19.9 after rebuilding ridges, and 20.7 after harvest. Greater OMCs in furrows were attributed to residue accumulations. Shifting of surface soil and exposur of subsurface soil at planting reduced OMCs on ridges. Mean OMCs were greater for RT than for CT because CT mixed residues throughout the tillage depth whereas RT maintained residues at the surface. Mean WSA was greater on ridges (58%) than in furrows (48%), presumably because more-stable aggregates were moved to ridges by the ridge-rebuilding operation. Ridge and furrow positions and possibly even ridge-side positions must be sampled to obtain representative OMC and WSA data from ridge tillage soil, especially where ridge tops are cleared at planting. Also, surface clearing should be limited at planting so that some residues and stable aggregates will remain at the surface to reduce soil crusting and seedling emergence problems. Technical Abstract: Soil surface conditions improve with increases in organic matter concentration (OMC) and water-stable aggregation (WSA), but surface variability may influence results obtained at sampling. The hypothesis was that cultural operations for sorghum [Sorghum bicolor (L.) Moench] would result in zones of differing soil OMC and WSA. This study determined cultural operation effects on OMC and WSA of soil used for sorghum. Pullman soil (Torrertic Paleustoll) was sampled in furrows, on ridge tops, and on ridge sides before planting and after planting, rebuilding ridges, and harvest in 1992. Tillage [conventional (CT) and ridge [early (RT-E) or late (RT-L) stalk shredding]], position, and sampling time affected OMC and WSA. Mean OMC (g kg**-1) was 19.1 with CT, 20.7 with RT-E, and 21.4 with RT-L; 19.5 (mean) on ridge top and side positions and 22.7 in traffic and 20.6 in non-traffic furrows; and 22.0 before planting, 18.8 after planting, ,19.9 after rebuilding ridges, and 20.7 after harvest. Greater OMCs in furrows were attributed to residue accumulations. Shifting of surface soil and exposure of subsurface soil at planting reduced OMCs on ridges. Mean OMCs were greater for RT than for CT because CT mixed residues throughout the tillage depth whereas RT maintained residues at the surface. Mean WSA was 58% on ridges and 48% in furrows, presumably because more-stable aggregates were moved to ridges by the ridge-rebuilding operation. Ridge and furrow positions and possibly even ridge-side positions must be sampled to obtain representative OMC and WSA data from RT soil, especially where ridge tops are cleared at planting. Ridge clearing should be limited at planting because removing most residues could cause soil crusting and seedling emergence problems. |
