Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Summary

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Abstract

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO₃) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO₃ and changes in elevation consistent with the conceptual model; CaCO₃ generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO₃ to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO₃.

Introduction

Soil erosion threatens the sustainability of agricultural lands. Crop management, such as a conventionally-tilled winter wheat-fallow crop rotation, can accelerate erosion and deposition processes as bare soils during fallow periods are more susceptible to wind and water forces^1,2,3,4,5 (Figure 1). While these processes might be evident, they can be difficult to quantify.

The purpose of this study is first to provide an efficient method for quantifyi....

Protocol

1. Land Surface Elevation Data Collection

1. GPS calibration for site
   1. Locate or set a stable benchmark in a secure location at the survey site for use as the base station GPS for RTKGPS data collection.
   2. Set up base station for RTKGPS data collection at this local benchmark using best approximation of coordinates for the base station location (i.e., WAAS-corrected GPS position).
   3. With the rover GPS, visit at least three horizontal and vertical control point benchmarks within the radio communication limits of the RTKGPS (approximately 10 km radius) and record positions.
      NOTE: Benchmarks described by the National G....

Results

Mapping DEM differences from 2001 and 2009 reveals erosion (red) and deposition (green) over that 8-year period, with decimeter-level changes in elevation over most areas (Figure 5). At the field-scale, erosion is dominant in the west and southwest, while deposition is seen along a northwest to southeast diagonal band on the eastern side of the field. Alternating bands of erosion and deposition are seen at the management-scale, often with abrupt changes at th.......

Discussion

Mapped changes in elevation (Figure 5) illustrate significant erosion and deposition on an agricultural field and spatial patterns indicative of multiple controlling factors over multiple scales. From field scale patterns associated with wind, down to fine scale dendritic patterns produced by water flow, processes relevant to this study are discernable. The level of elevation change detection provided by repeated RTKGPS ground surveys appears optimal. Finer detection levels, as provided by T.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Real-time kinematic GPS system	Trimble	Model 5800
GPS field data collector	Trimble	Model TSC2
GPS field software	Trimble		Trimble Access (Trimble Survey Controller used in 2001 for site calibration but this software is no longer supported)
Hydraulic soil coring machine	Giddings Machine Company
Utility vehicle	John Deere	Gator 6x4
GIS software	ESRI		ArcGIS for Desktop with Spatial Analyst and Geostatistical Analyst Extensions
Statistical software	SAS		SAS Institute Inc.
Pressure transducer 0-105 kPa	Serta	Model 280E	Setra Systems, In., Boxborough, MA
Volt meter	WaveTek	5XL	Digital meter set to read volts
Serum Bottles	Wheaton	223747	100 mL
Serum Bottles	Wheaton	223762	20 mL
Sealing Cap 20 mm Aluminum	Wheaton	224183-01	Case of 1,000
20 mm gray butyl stopper (2-prong)	Wheaton	224100-192	Septum; Case of 1,000
Hand crimper	Wheaton	W225303	20 mm size
Hand Decapper	Wheaton	W225353	20 mm size
Acid vials	Wheaton	224881	0.50 dram size (2-mL)
Power supply	SR Components	DDU240060	Class 2 Transformer AC adaptor; Input 120VAC , Output 24VDC
Calcium carbonate	Fisher	471-34-1	500 g of 100% w/w CaCO3