Temporal variation of soil physical properties following moldboard plowing and direct drilling of a sand loam soil

355 wheat/corn crop rotation. Data analysis of the soil macrostructure of a plot cropped to corn, reveals information concerning variations in soll structure resulting from different cultivation practices, as well as the evolution of soil structure over the years. Direct-drilled soils generally have a greater bulk density, and the greater strength of direct-drilled plots compared to cultivated land is obvious. Changes also occur in deeper parts of the profile, where deeper and more continuous crack development is visible on penetrometer profiles.

EFFECT OF TILLAGE SYSTEMS ON SOIL CHARACTERISTICS R.C.M. BISCAIA and G.S. DE FARIAS IAPAR, Polo de Curitiba,

P.O. Box 1493, 80.000 Curitiba-Parana

(Brazil)

Three tillage systems are tested: conventional, minimum and no-tillage. The poster shows all the operations and equipment used in each system. The tillage systems are used with 5 crop rotations, and physical parameters of the soil and crop yields are evaluated.

TEMPORAL VARIATION OF SOIL PHYSICAL PROPERTIES FOLLOWING MOLDBOARD PLOWING AND DIRECT DRILLING OF A SANDY LOAM SOIL M.R. CARTER Agriculture Canada, CIA 7M8 (Canada)

Research Station,

Charlottetown,

Prince Edward Island,

Tillage studies were conducted for 2 years on a Charlottetown sandy loam, an Orthic Humo-Ferrlc Podzol (Haplorthod). The study evaluated the initial change and subsequent short-term variation in soll physical properties, induced by moldboard plowing and direct drilling for spring cereals. Transient soil properties, such as bulk density, macropores (effective diameters of >300 ~m and 300-50 ~m), pore continuity (saturated hydraulic conductivity), and soll strength were measured prior to, during, and after the growing season, to characterize the durability of soll loosening provided by the moldboard plowing treatment. Soil loosening caused an initial decrease in bulk density and soil strength, and an increase in macropores and pore continuity, compared to the direct-drilled soil. This loosening effect was gradually dissipated, due to the processes of precipitation and soil desiccation, over a 12-month period. Temporal variations in macropores and pore continuity were also associated with biological processes during the growing season, such as root growth and earthworm activity.

AGRONOMIC COMPARISON BETWEEN DIFFERENT SOIL TILLAGE TECHNIQUES APPLIED TO A CORN-COTTON SEQUENCE IN THE IVORY COAST J.L. CHOPART IDESSA-CIRAD,

Soll Physics Section,

Central Ivory Coast (West Africa)

P.O. Box 635, Bouak~ (Ivory Coast) experiences

2 rainy seasons per year,

from