Assessment of Soil Quality on TSN Plots at Ellerslie and Breton Utilizing Physical, Chemical, and Biological Properties

Assess the impact of consistent management, tilled vs no-till, straw removed or not, and N application rate on soil quality using physical, chemical and biological properties at Ellerslie and Breton, AB.

IPNI-2007-CAN-AB25

21 Dec 2007

Methodology


Experimental Design: The TSN (Tillage-straw-nitrogen) plots were set up at the Ellerslie and Breton Research sites in 1979. The experiential design for these sites was a randomized block consisting of 10 treatments x 4 replicates as shown on Table 1. These plots have been in consistent management for 28 years and are being prepared for a reverse tillage experiment which will be conducted in 2008.

Table 1. Experimental design for the TSN Plots at Ellerslie and Breton
Treatment
Tillage
Straw
N rate
Placement
1
No till
No Straw
0
2
Tilled
No Straw
0
3
No till
Straw
50
Banded
4
No till
Straw
0
5
Tilled
Straw
0
6
No till
Straw
100
Banded
7
Tilled
Straw
100
Banded
8
Tilled
Straw
50
Banded
9
Tilled
No Straw
50
Broadcast & Incorp.
10
Tilled
No Straw
50
Banded

These plots have been sampled in May 2007 to assess the carbon sequestration, N pools, dry aggregate size distribution, N mineralization potential, etc. In order to assess changes in soil quality over a period of 28 years, a list of potential soil parameters to assess (i) soil structure and soil-air-water relations; (ii) biological indicators; (iii) macronutrient supply indicators; and (iv) salinity indicators has been drawn up (Table 2).

Table 2. List of potential soil parameters

(i) Soil Structure and Soil-Air-Water Relations
IndicatorSoil quality information
Dry- and wet-aggregation indices and water stability indexThe water stability index is a ratio of wet/dry aggregate indices and can provide information of stability of soil structure
Bulk density/ penetration resistanceSoil compaction, physical environment for roots and soil organisms. Bulk density is needed to calculate volumetric moisture content
TextureThis is a master variable and needs to be measured
Aeration porosity to a specified tension, e.g. 50 cm of waterThis class of porosity controls infiltration, drainage and aeration and is most affected by soil disturbance
Available soil moistureThis is an important parameter for assessing vegetation growth potential
Effective rooting depthPlant roots provide a visual evidence of the degree of soil disturbance

(ii) Biological Parameters
IndicatorSoil quality information
Total Organic COrganic matter reserves, biological resources
Total Organic NOrganic N reserves, organic matter quality
Microbial biomass C and NSize of microbiological population, rapidly cycling, organic matter, and nutrients.
Microbial C/ Total organic C ratioEcosystem stability; C cycling ratios; soil organic matter quality
CO2 productionAvailability of organic matter reserve, microbial activity.
Respired C/ microbial C ratioRespiratory quotient.
Microbial N/ Total organic N ratioEcosystem stability; N cycling ratios; soil organic matter quality
Mineralized N/ microbial N ratioSpecific N mineralization rate.
Soil meso- and macro-faunaIndicator of a healthy food web

(iii) Macronutrient Supply Parameters
IndicatorSoil quality information
Potentially-mineralizable NPotential of a soil to supply plant-available N
Kelowna PPlant-available phosphate.
Available KPlant-available potassium.
Available SPlant-available sulfur.
pH
in-situ nutrient supplyPlant Root Simulator (PRS) Probes

(iv) Salinity Parameters
IndicatorSoil quality information
Reaction (pH) Acidity or alkalinity of soil.
Salinity (EC) (dS/m) Degree of salinity
Sodicity (SAR) Degree of sodicity
Caption-exchange capacityBuffering capacity and ability to retain nutrients. Derived measurements provide the sum of cations, base saturation and ESP
Saturation (%) Moisture saturation
Stoniness Class Degree of stoniness
Texture Mater variable
Moist Consistency Soil structure parameter
CaC03 Equivalent (%) Affects SAR and ESP calculations
Gypsum (%) Affects SAR and ESP calculations

Timelines
Ellerslie site (if funding is approved for 2007)
Select and sample the Ellerslie site in the week of June 25 to June 30, 2007
Order supplies and start incubation experiments and measurement of microbial C and N (July and August, 2007)
Determine moisture retention curves, wet and dry aggregate size distribution and texture (Aug./Sept, 2007)
Fit in other items listed in Table 1 in between the above measurements (July to September)
Compile data and conduct statistical analysis

Breton site (If funding is approved for 2008)
Select and sample the Breton site in the week of July 9 to July 13, 2007.
Order supplies and start incubation experiments and measurement of microbial C and N
(August to September, 2007)

Determine moisture retention curves, wet and dry aggregate size distribution and texture (Oct./Nov., 2007)
Fit in other items listed in Table 1 in between the above measurements (August to December, 2007)
Compile data and conduct statistical analysis

Sampling and Methods of Analysis
For soil moisture retention curve and macroporosity:
Install and remove metal rings (5 cm OD x 3 cm deep) with undisturbed soil at 4 depths: 1-4; 6-9; 11-14; 16-19 cm; 5 rings per depth so we do not have to re-saturate cores for the different pressures. Samples are to be refrigerated, not dried.

For wet and dry aggregation:
(sample will be divided into half, where half will be used for wet aggregation, half for dry aggregation).

To complement what Dr Malhi has sampled already for dry aggregation; excavate a slice of soil (approx 20 x 30 cm) with flat spade; 4 depths 0-5; 5-10; 10-15; 15-20 cm

For microbial C and N, C and Net mineralization, specific C and N mineralization and mineralizable N; texture;
Three composite core samples per treatment: 0-5; 5-10; 10-15, 15-20 cm depths. Samples are to be refrigerated immediately after sampling.

For infiltration: in situ measurements using the Guelph permeameter.