Quantitative indicators of soil quality

Transcription

1 Quantitative indicators of soil quality What measurements should I make or what can I observe that will help me evaluate the effects of management on soil function now and in the future? Too often scientists confine their interests and efforts to the discipline with which they are most familiar (Doran and Parkin, 1996). Soil quality and health indicators must be holistic not reductionistic.

2 Soil quality indicators (Parkin 1994)

3 The more the better? High rates of respiration may be ecologically detrimental due to depletion of soil organic C. Levels of mineralizable nitrogen above crop needs may cause environmental contamination. Soil property Respiration (µl O 2 h -1 g -1 ) Mineralizable N (mg kg -1 ) Biodynamic farms Conventional farms Ratio * *

4 A performance-based index of soil quality An evaluation of soil function Sustainable production Environmental quality Human and animal health A soil quality (SQ) consists of six elements: SQ = f (SQE1, SQE2, SQE3, SQE4, SQE5, SQE6) where Soil Quality Elements are SQE1 = food and fiber production SQE2 = erosivity SQE3 = groundwater quality SQE4 = surface water quality SQE5 = air quality; and SQE6 = food quality

5 Farm-based assessment of soil quality Soil health is a more integrative term preferred by some farmers to soil quality and is assessed by farmers using indicator properties of both soil and nonsoil target systems (Harris and Bezdicek, 1994). Farmers use qualitative or sensory means in addition to quantitative data. Documents changes that occur due to management

6 Wisconsin Soil Health Scoreboard Interview method Explores the question: How do you recognize a healthy soil? performed on the farm and recorded on tape for further analysis Twp stages of interview: open-ended questions and questions related to specific properties of soil health but farmers have not addressed

7 Indicators used in a soil health scorecard The most important properties were chosen if they were: used by the majority of the farmers mentioned earlier and more frequently mentioned in the open-ended question period rather than being promoted by closed-ended questions All descriptions of healthy and unhealthy soil for each indicator property cataloged

8 Development of an assessment tool Scaled items Transforming a qualitative nature to an index Literature was reviewed to define health and deal with issues of scaling. Based on the capacity of a soil to perform certain functions and attributes or vital statistics (e.g. soil color and structure, earthworms and others)

9 Rating scales Healthy: Performance of function is optimal and structure is normal Impaired: An abnormality in function and/or structure Unhealthy: Severe restriction or inability to perform function considered normal, severe deformity or loss of structure, disabled Majority of indicator properties are subjectively measured by the sense (look, smell, or feel). Ordinal level of measurement rather than exact magnitude of difference among categories

10 Rating practices Soil erosion Healthy, impaired, or unhealthy?

11 Tillage Rating practices (cont d) rvation%20tillage

12 Rating practices (cont d) Soil structure

13 Rating practices (cont d) Infiltration

14 Rating practices (cont d) Micronutrients

15 Rating practices (cont d) Organic matter oil_structure.html (Huang et al. 2010)

16 Farm-based scorecard Primarily uses sensory-perceived or descriptive indicator properties. Observation made throughout the growing season and is best completed near or just follow harvest (soil health over time). Healthy (3 to 4), impaired ( ), and unhealthy (0 to 1) All indicators are equally important. Certain properties graded low may need attention.

17 Farm-based scorecard (cont d) Biased rating (e.g. not familiar with different soil types) Indicators may not be used for both organic and conventional farming. When judging any property, farmers may also judge management practices. Modification of the scorecard for other cropping systems and regions.

18 Applications of farm-based scorecard Served as a communication bridge between farmers and scientists Integrative assessment of the overall effect of management on soil health Monitor soil health over time Farmers can adjust their management practices based on their own analyses. Provide a base to identify and develop both descriptive and analytical soil and nonsoil indicators

19 Farm-based scorecard example