A Protocol for Collecting and Constructing Soil Core Lysimeters

Summary

A detailed method for extraction and assembly of intact soil core lysimeters and their use for study of leachate and associated loss of nutrients from surface applied poultry litter is demonstrated.

Abstract

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the landscape has complex and varied soil morphology, an accompanying disparity in flow paths for leachate through the soil macropore and matrix structure is present. The rate of flow through these paths is further affected by antecedent soil moisture. Lysimeters are used to quantify flow rate, volume of water and concentration of nutrients leaching downward through soils. While many lysimeter designs exist, accurately determining the volume of water and mass balance of nutrients is best accomplished with bounded lysimeters that leave the natural soil structure intact.

Here we present a detailed method for the extraction and construction of soil core lysimeters equipped with soil moisture sensors at 5 cm and 25 cm depths. Lysimeters from four different Coastal Plain soils (Bojac, Evesboro, Quindocqua and Sassafras) were collected on the Delmarva Peninsula and moved to an indoor climate controlled facility. Soils were irrigated once weekly with the equivalent of 2 cm of rainfall to draw down soil nitrate-N concentrations. At the end of the draw down period, poultry litter was applied (162 kg TN ha^-1) and leaching was resumed for an additional five weeks. Total recovery of applied irrigation water varied from 71% to 85%. Nitrate-N concentration varied over the course of the study from an average of 27.1 mg L^-1 before litter application to 40.3 mg L^-1 following litter application. While greatest flux of nutrients was measured in soils dominated by coarse sand (Sassafras) the greatest immediate flux occurred from the finest textured soil with pronounced macropore development (Quindocqua).

Introduction

The Delmarva Peninsula borders the eastern shore of the Chesapeake Bay, and is the home to one of largest poultry production regions in the US. Roughly 600 million chickens and an estimated 750,000 tons of manure are generated from the production of these birds each year¹. Most of the manure is used locally as a fertilizer amendment on agricultural fields. Because of historically high rates of manure application, nutrients such as nitrogen and phosphorus have accumulated in the soil and are now susceptible to off-site losses via subsurface leaching². Much of the groundwater flow is directed toward an extensive network of ditches that ultimately d....

Protocol

1. Preparing the Materials

1. Cut the main body of the lysimeter from 30.5 cm (12 inch) diameter (ID; nominal) schedule 80 PVC; this has a wall thickness of 1.9 cm (0.75 inch) (Figure 1a). Cut the length of the lysimeter body depending on the thickness of the soil layer(s) to be studied; here, use a 53 cm (21 inch) long body. Rout a 0.63 cm deep by 45° bevel around the bottom end of the lysimeter to form a sharp leading edge on the inside wall of the lysimeter body to aid in cutting through the soil.
2. Modify a 34.5 cm ID, flat bottom PVC cap by gluing a 15.3 cm tall 30.5 cm ID ring of schedule 80 PVC into the cap to allow for fr....

Results

Soil moisture, leachate depth and leachate chemistry all illustrate variability across soils, revealing differences as a function of soil properties despite internal variability between replicate soil core lysimeters of a particular soil. The later point warrants particular note from the standpoint of experimental design, as inherent variability in soil moisture and leaching processes requires considerable replication to minimize type 2 statistical error. In the current study, coefficient.......

Discussion

Important steps of lysimeter Collection

Leaching studies illustrate the influence of soil properties and manure management on nitrogen losses to shallow groundwater. Soil physical properties such as soil texture, aggregate structure and bulk density mediate the percolation of water and solutes. Accurately determining leachate volume and solute concentrations is dependent upon retaining the integrity of these soil physical properties during lysimeter collection by following these critical steps.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Schedule 80 PVC Pipe	Fry's Plastic	Call	Sold in 10 ft lengths
Fernco Fittings	Fry's Plastic	Call	12 inch diameter
Type II PVC plates for perforated discs	AIN Plastic	Call	Sold in 4' x 8' sheets of PVC II Vintec II
Schedule 40 PVC Caps	Fry's Plastic	Call	12 inch diameter
Stainless Steel Screws	Fastenal	135716	#8 Bugle Head Phillips Drive Sharp Point Grade 18-8 Stainless Steel
Silicone II Caulk	Lowe's	447488
Nylon Tube Fitting	United State's Plastic Corp.	61137	0.5 inch NPT
Foodgrade Tubing	Lowe's	443209	0.5 inch vinyl