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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #83654
Title: LEAST LIMITING WATER RANGE:LONG TERM TILLAGE INFLUENCES IN A WEBSTER SOIL

Author
item BETZ, C - UNIVERSITY OF MINNESOTA
item Allmaras, Raymond
item COPELAND, STEPHEN
item RANDALL, G - UNIVERSITY OF MINNESOTA

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant rooting may be limited by any combination of available water, poor aeration, and soil resistance to root elongation. Field assessments of rooting limitations due to compaction and tillage management are sparse and often inaccurate enough to prevent a true understanding of the potential role of soil compaction and tillage management in long term sustainable agriculture. A method was developed to show, in a simple diagram of soil water content and soil density, how compaction and long-term tillage modify the hospitality zone for rooting in a fine-textured poorly drained soil. Conservation tillage systems must provide both good surface conditions for infiltration and good internal drainage, but the study demonstrated that poor internal drainage developed because the depth of tillage was reduced in the conservation tillage systems. If conservation tillage systems are to be successful in poorly drained soils, a tillage scheme must be developed to retain residues on the surface and to retain good internal drainage-thi is a machinery development problem. The information in this publication will be useful to Extension and others to consider drainage classification in their recommendations about conservation tillage systems.

Technical Abstract: Root growth and function is a continuum response to soil physical environment, but root responses in the field are sufficiently complex to require a least limiting approach. Individual rooting limitations of available water , soil aeration, and penetration resistance are linked to construct a least limiting water range (LLWR) as a function of bulk density. The LLWR concept was evaluated at two depths in a poorly-drained clay loam: 1) the 5 to 10-cm depth in non-tracked and tracked interrows of three long-term tillage treatments (chisel plow-CH, moldboard plow-MB, and no-till-NT), and 2) a plow pan at 25 to 30-cm depth. Laboratory measurements of bulk density, shrinkage, saturated hydraulic conductivity, water retention characteristic (WRC), and penetration resistance characteristic (PRC) were obtained from undisturbed soil cores. Linearized fits of the WRC and PRC with R**2 greater than 0.70, were sensitive to tracking and CH vs MB tillage; tracking the NT and the plow pan reduced by 75 percent the impact of bulk density on the PRC. Tracking reduced the LLWR especially in CH and NT treatments, but had a lesser effect in MB than CH tillage. Penetration resistance was more restricting than the wilting point in the NT treatment and the plow pan, but in the other treatments the inverse dominated. This test of the LLWR portrayed a major impact of soil structure management on physical control of rooting. The LLWR also explained significant difficulties with conservation tillage in this soil.