Field experiments were conducted to evaluate the performance of two recently developed in situ techniques to measure saturated hydraulic conductivity (K). These two techniques are (1) the constant-head well permeameter method using the Guelph permeameter, and (2) the falling-head permeameter method using the velocity permeameter. K was measured on a silt loam soil at eight sites and for four different depths (150, 300, 450, 600 mm) at each site by using these two techniques. K determinations were also made in the laboratory by using a constant-head permeameter on undisturbed soil columns collected from all test sites and depths. Measurements of K for the selected test sites and conditions indicate that Guelph and velocity permeameters provided reasonably similar values. Both methods are simple to use and easily portable, and both produce results in a relatively short time (usually 15 min to 20 min for the velocity permeameter and 60 min to 90 min for the Guelph permeameter for a single measurement). Field-measured K values tended to be much lower than laboratory values. Disciplines

Mean penetration resistance before tillage and depth at Faisalabad Mean penetration resistance after tillage and depth at Faisalabad Mean penetration resistance before tillage and depth at Pirsabaq Mean penetration resistance after tillage and depth at Pirsabaq Mean surface roughness coefficient for before and after tillage treatments Mean emergence count as affected by tillage at Islamabad Mean emergence count as affected by tillage at Faisalabad Mean emergence count as affected by tillage at Pirsabaq 1 I. INTRODUCTION Tillage has been a dominant activity in agriculture from the beginning of civilization. Principal reasons for tillage were to establish and maintain a crop free of weeds (Cannell, 1985), bury plant materials (Sprague, 1986), mix lower horizons with surface layers (Sprague, 1986), loosen the surface for water movement (Unger and Fulton, 1990), aid seed placement, encourage emergence (McCalla, 1967), and reduce weeds, insects and diseases. Changes in tillage procedures, practices, tools, and in tillage terminologies have also occurred with the passage of time. These changes were basically crop-oriented, soil-oriented and labor-oriented. Tillage tools have evolved from rudimentary ones operated by humans to more sophisticated ones powered by animals and, eventually, by machines (Schafer and Johnson, 1982). When shifting from moldboard plow to a disk, from a cultivator to a rotary tiller, or from extensive tillage to limited tillage, we change the seed environment that is created. In other words, a change in tillage will cause a change in resulting physical properties (Cassel, 1982). These properties include bulk density, soil moisture, and nutrient availability. Tillage operations, regardless of the tillage implement, alter soil physical properties. The soil may be 2 loosened, granulated, compacted, crushed, inverted, sheared, or shattered (Cassel, 1982). In short any manipulation that changes soil condition may be considered tillage, but there is limited information available concerning tillage-induced soil changes (Gantzer and Blake, 1978; Erbach et al., 1986). To understand tillage effects on a given soil physical property, one must also consider the effects on related physical properties (Hill, 1990). Ehlers (1984) reviewed tillage research and mentioned that little effort has been spent trying to understand how the soil physical factors actually influence plant growth and yield. The same is true for the transmission of external forces within the soil and the effect of these forces on the arrangement of soil particles and pore spaces (Ehlers, 1982). Economic considerations and physical limitations force us to consider, how deep and how much to till. Excess tillage overpulverizes the soil and accelerates the loss of soil moisture and organic matter (Sprague, 1986). Less tillage may reduce yield by not providing the required seed environment (Griffith et al., 1986). Progress in tillage research has been greatly hindered by the presence of the many soil and weather variables which affect tillage res...