|Strickland, Timothy - Tim|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2004
Publication Date: 1/4/2004
Citation: Hubbard, R.K., Phatak, S.C., Reed, R., Strickland, T.C. 2004. The effects of conservation tillage and cover crops on physical properties of coastal plain soils [abstract]. Agronomy Abstracts. January 04, 2004. CDROM.
Technical Abstract: The physical properties of soils affect crop growth and movement of water and solutes. Crop growth is affected by soil moisture retention, which relates to particle and pore size distribution and bulk density. Movement of solutes is largely affected by water movement routes and transport rates. Leaching of solutes closely relates to soil hydraulic conductivity which depends on particle size distribution, porosity, and bulk density. Uncertainty exists about the impact of conservation tillage on the total agricultural environment. Many researchers have shown that water infiltration occurs at a faster rate under no-till than conventional-till because of surface cover and development of macropores. However, other researchers have found less solute leaching in no-till plots as compared to conventional till plots. It has also been concluded that conservation tillage may increase or decrease solute leaching in the short term depending upon soil and other factors. Two studies were initiated by USDA-ARS and University of Georgia scientists to assess the effects of conservation tillage and cover crops on the physical properties of Coastal Plain soils. The first study compared soil physical properties between land which had been in long term conservation tillage (greater than 15 years) and land which has always had conventional tillage. The second study is comparing soil physical properties under different cover crops combined with conservation tillage. For both studies replicated minimally disturbed soil cores were collected from each plot using an impact sampler. Measurements were made on these cores of saturated hydraulic conductivity, soil moisture retention, and bulk density. The constant head method was used for saturated hydraulic conductivity while soil moisture retention was measured using tempe cells and pressure plates. The comparison of long term conservation tillage versus conventional tillage showed that the greatest difference in soil physical properties was in the volumetric water content of the surface soil (0-7.5 cm) at field capacity. Much more water was held by the soil in long-term conservation tillage than the soil in conventional tillage. Hence more water was available to crops in the conservation tillage treatment. The cover crop study includes rotations of sunnhemp, lupin, or fallow with sweet corn and cucumbers. Measurements of soil physical properties in the conservation tillage-cover crop study showed that significant differences had not occurred within 1 and1/2 years of implementation of these systems. This paper summarizes soil physical property findings from both the long term and conservation tillage-cover crop studies.