Large Soil Monoliths Research Articles

Pulldown forces for collecting large soil monoliths : A. D. Schneider, J. L. Steiner & T. A. Howell, Transactions — American Society of Agricultural Engineers, 37(3), 1994, pp 831–835

Pulldown forces for collecting large soil monoliths : A. D. Schneider, J. L. Steiner & T. A. Howell, Transactions — American Society of Agricultural Engineers, 37(3), 1994, pp 831–835

Pulldown Forces for Collecting Large Soil Monoliths

The force for pulling down large, steel monolith tanks was measured for a fine sandy loam, a silt loam, and clay loam soil with varying soil water contents in two of the soils. Pressure gages on hydraulic jacking equipment were used to measure force as a function of depth throughout the 2.4-m installation depth of the soil monolith tanks. Monolith tank areas were 0.75 1.00 m or 3.00 3.00 m, and the tank wall thickness was 9.5 mm. Except for the effects of natural hard pans or plow pans, pulldown force was linearly related to depth. When pulldown force was converted to wall friction, the average wall friction after wetting for each of the three soils was about 20 kPa. For most agricultural soils without rocks or cemented layers, the monolith tank wall friction from prewetted soil should also be less than 20 kPa. Wall friction variability decreased with depth so that a safety factor of 1.25 would be satisfactory in designing monolith collection equipment.

Design, Installation, and Performance of Percolation Lysimeters for Water Quality Sampling

Lysimeters are the primary research tool for measuring percolation and water quality. Monolithic percolation lysimeters were evaluated for measuring the quantity and quality of leachate from the root zone of irrigated crops. Six percolation lysimeters were installed in a continuous corn (Zea Mays, L.) cropping system near North Platte, Nebraska, during the fall of 1988 and spring 1989. The lysimeters were 0.9 m in diameter and 2.4 m deep. They were filled with undisturbed soil using a hydraulic pull-down method. Porous stainless steel extractors were installed vertically upward into the lysimeter bottoms, and leachate was extracted from the unsaturated soil. Leachate volume, volumetric soil water content, soil temperature, and soil bulk density were measured. Isolation of a large soil monolith in the lysimeter did not significantly affect plant growth, soil bulk density, or temperature. Soil water content near the lysimeter bottoms was greater than in the surrounding field after a wet spring in 1991. However, extractors removed most excess water and adequately matched unsaturated drainage in the field. Though leachate varied among lysimeters, they behaved similarly over time. Results will help relate irrigation management and scheduling strategies to potential leaching of soil water and associated chemicals into groundwater.

Lysimeters Without Edge Flow: An Improved Design and Sampling Procedure

A description is given of a modified lysimeter design and sampling procedure designed to prevent edge flow from occuring in large soil monolith lysimeters. An internal cutting ring at the base of the lysimeter casing produced a small annular gap between the soil monolith and the wall of the casing. This gap was filled with liquefied petrolatum, which provided a water-tight seal around the edge of the lysimeter. Water and solutes were unable to leak between the monolith and casing. The use of petrolatum as a sealant is suitable for waterflux and nutrient-leaching studies, but is not suitable for pesticide

Hydraulic Pulldown Procedure for Collecting Large Soil Monoliths

ABSTRACT SOIL monoliths 3-m (9.8-ft) square and 2.4-m (7.8-ft) deep were collected by hydraulically jacking bottomless steel boxes into a clay loam soil. Four jacking assemblies that utilized commercially availabe 178-kN (40,000-lb) hydraulic jacks were anchored to bell-bottomed piers at the corners of the steel boxes. A pulldown frame supported the jacking assemblies over the piers and uniformly distributed the pulldown force over the 9.5-mm (3/8-in.) thick walls of the steel boxes. Soil around the walls of the steel boxes was excavated as the boxes were jacked down. The procedure is a major advance in the collection of large soil monoliths. Bell-bottomed piers or similar anchors provide larger pulldown forces than are practical with deadweights, and hydraulic jacks or cylinders offer precise control of the downward movement. The technique is economically feasible for large soil monoliths, especially where the pulldown equipment can be reused to collect several monoliths.

A Procedure for Placing Large Undisturbed Monoliths in Lysimeters

AbstractIncreasing need for studies of leaching water and possible pollutants through soil profiles led to the development of a method for placing large undisturbed soil monoliths in metal boxes for use as drainage lysimeters. Materials and equipment used in the technique are usually available or can be leased from local contractors. Monoliths as large as 1.5 m deep and with surface areas of 3 m have been taken. The technique could be used for even larger monoliths. Thus far, lysimeters have been installed in clay, sandy clay, loam and sand soils. The upper lip of several of the lysimeters described here was buried 25 cm below the surface to allow normal tillage, bed preparation and furrow irrigation.