Module

Applied Activity Part 5: Soil Tests for Indicators of Sustainability

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Applied Activity #5:

Soil Tests for Indicators of Sustainability

 

Overview: In this applied activity, you’ll assess the resilience and sustainability of the soil in your agroecosystem. For this activity, we will be drawing from the methodologies and findings from the paper “A Rapid, Farmer-Friendly Agroecological Method to Estimate Soil Quality and Crop Health in Vineyard Systems” by Nicholls et al.

According to Nicholls et al., “Sustainability is defined as a group of agroecological requisites that must be satisfied by any farm, independent of management, economic level, or landscape position” (34). Soil quality and crop health are requisites for agroecosystem sustainability, as well as being indicators of overall agroecosystem sustainability.

Measuring soil quality can require expensive and time-consuming soil tests, which aren’t accessible to many farmers. However, Nicholls et al. developed a practical methodology for soil quality and crop health. As part of the paper, farmers developed sustainability requirements of agroecosystems, and with the researchers, developed 10 indicators of crop health and 10 indicators of soil quality, which these tests measure. You’ll use this same methodology to conduct farmer-friendly tests of your soil to measure soil physical characteristics, as well as soil ecosystem diversity and health.

As you complete the soil tests, you’ll assign a numerical value between 0-10 to each indicator using the guidelines in the chart below. You’ll be using the same indicators as other farmers, making your results easily comparable. “As all the measurements made are based on the same indicators, the results are comparable and it is possible to follow the evolution of the same agroecosystem along a timeline, or make comparisons between farms in various transitional stages.  Most importantly, once the indicators are applied, each farmer can visualize the conditions of his/her farm, noticing which of the soil or plant attributes are sufficient or deficient compared to a pre-established threshold (Nicholls et al. 34).”

After you have assigned each indicator a numerical value, you’ll compile an “amoeba graph” for each soil quality and crop health. Amoeba graphs are valuable, as, “it allows one to visualize the general status of soil quality and crop health, considering that the closer the amoeba approaches the full diameter length of the circle the more sustainable the system (a 10 value). The amoeba shows which indicators are weak (below 5) allowing farmers to prioritize the agroecological interventions necessary to correct soil, crop or system deficiencies.” (36)

As an added benefit, farmers can compare their amoeba graphs with one another. “By applying the methodology simultaneously to several farms it is possible to visualize which farms exhibit low or high values of sustainability…The idea here is not for farmers to copy the techniques that lighthouse farmers use, but rather to emulate the processes, synergisms and interactions that emerge from the ecological infrastructure of the lighthouse farm (farms with “above-average” 5+ sustainability values), which are assumed to determine the successful performance of such systems in terms of soil quality and crop health. Simply copying the practices used by successful farmers does not work for diffusing principles underlying the performance of lighthouse farms. Agroecological performance is linked to processes optimized by diversified systems and not to specific techniques” (Altieri 1995).

To learn more about these methods, please read the paper below:

A Rapid, Farmer-Friendly Agroecological Method to Estimate Soil Quality and Crop Health in Vineyard Systems” by: C. I. Nicholls, M. A. Altieri, A. Dezanet, M. Lana, D. Feistauer edited by: The Bio-Dynamic Farming and Gardening Association Wyoming US Bio-dynamics : a periodical furthering soil conservation and increased fertility in order to improve nutrition and health, No. 250. (2004), pp. 33-40  Key: citeulike:9070269

Instructions for Applied Activity:

  1. Review Examples below, then scroll below to fill measure your own soil quality
  2. Measure each indicator by conducting a simple test using the soil at your field site.
  3. Using Table 1, estimate the value of your soil as compared to the established value
  4. Create an amoeba graph for each soil quality and crop health.

 

EXAMPLES:

Table 1. EXAMPLE Soil quality and crop health indicators in grape systems, with its corresponding characteristics and values (values between 1-10 can be assigned to each indicator, 1 being the least desirable value, 5 a moderate or threshold value and 10 the most preferred value).

 

Table 2. EXAMPLE Assigned soil quality and crop health indicator values in an organic-biodynamic vineyard (Benziger) and a transitional vineyard (Cain) in northern California.

Indicators Benziger vineyard (Organic-Biodynamic) Cain vineyard (Transition)
Soil quality

1.        Structure

2.        Compaction

3.        Soil depth

4.        Status of residues

5.        Color, odor and organic matter

6.        Water retention (moisture level)

7.        Soil cover

8.        Erosion

9.        Invertebrate presence

10.           Microbiological activity

Average of soil quality

7

7

6

6

5

5

5

8.5

1

2.5

5.3

3.5

5

5

5.5

6

6

7

10

4

5

5.7

 

 

Crop health

1.         Appearance

2.         Crop growth

3.         Disease incidence

4.         Insect pest incidence

5.         Natural enemy abundance and diversity

6.         Weed competition and pressure

7.         Actual or potential yield

8.         Vegetational diversity

9.         Natural  surrounding vegetation

10.           Management system

Average of crop health

8.5

8.5

9

9.5

1.5

9

8

4

9

7

7,4

6.5

8

10

10

2

10

6

3.5

8

4

6.8

Figure 2.  EXAMPLE: Amoeba representing the soil quality status of two vineyards systems (Cain – transition and Benziger – biodynamic) in northern California.

Applied Activity: Measuring Indicators of Soil Quality and Crop Health

 Below, you’ll find a list of different indicators for soil quality, including a definition for each indicator (hyperlinks lead you to cited sources), as well as a description of how to measure for each indicator. After completing your simple test, record your estimated value for each.

Indicators of Soil Quality

Soil Structure: Refers to the arrangement of soil separates into units called soil aggregates. An aggregate possesses solids and pore space (from Plants and Soils eLibrary). For a simple test, take a handful of soil and break apart in your hands. Examine noting the characteristics below, and then match your sample to the scale on the left. 

Scale Characteristics Your estimated value
1 Loose, powdery soil without visible aggregates
5 Few aggregates that break with little pressure
10 Well formed aggregates that are difficult to break

 

Compaction: Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Heavily compacted soils contain few large pores and have a reduced rate of both water infiltration and drainage from the compacted layer (University of Minnesota Extension). To test, a wire flag is pushed vertically into the soil at various locations in your field. Record the depth at which it bends due to resistance in the soil.

 

Established value Characteristics Your estimated value
1 Compacted soil, flag bends readily
5 Thin compacted layer, some restrictions to a penetrating wire
10 No compaction, flag can penetrate all the way into the soil

 

Soil depth: The effective depth of a soil for plant growth is the vertical distance into the soil from the surface to a layer that essentially stops the downward growth of plant roots. The barrier layer may be rock, sand, gravel, heavy clay, or a cemented layer.

 

Established value Characteristics Your estimated value
1 Exposed subsoil
5 Thin superficial soil
10 Superficial soil (> 10 cms)

 

Status of residues: Refers to the stage of decomposition of organic matter in the soil. Test is simply done visually by examining a handful of soil.

 

Established value Characteristics Your estimated value
1 Slowly decomposing organic residues
5 Presence of last year’s decomposing residues
10 Residues in various stages of decomposition, most residues well decomposed

 

Color, odor and organic matter: Smell and examine your sample visually, looking particularly for the presence of humus.

 

Established value Characteristics Estimated value
1 Pale, chemical odor and no presence of humus
5 Light brown, odorless, some presence of humus
10 Dark brown, fresh odor and abundant humus

 

Water retention: The moisture level after irrigation or rain. Test: Take a fistful of your soil and squeeze it. Examine how it holds together – does it break apart? Does it form a loose ball? Does it compact? These things will tell you a lot about your water retention.

 

Established value Characteristics Estimated value
1 Dry soil, does not hold water
5 Limited moisture level available for short time
10 Reasonable moisture level for a reasonable period of time

 

Soil cover: Refers to the presence or absence of residue/biomass on the top of your soil.

 

Established value Characteristics Estimated value
1 Bare soil
5 Less than 50% soil covered by residues or live cover
10 More than 50% soil covered by residues or live cover

 

Erosion: The action of surface processes that transport materials in your soil from one location to another. This process can be visually identified.

 

Established value Characteristics Estimated value
1 Severe erosion, presence of small gullies
5 Evident but low erosion signs
10 No visible signs of erosion

 

Presence of invertebrates: Refers to the amount of animals without backbones in your soil (i.e. earthworms, flies, etc). Simply look for the creatures themselves or signs of their presence.

 

Established value Characteristics Estimated value
1 No signs of invertebrate presence or activity
5 A few earthworms and arthropods present
10 Abundant presence of invertrebate organisms 

Microbiological activity: To test: You can apply small amounts of water peroxide to a soil sample to observe its effervescence (amount of bubbles produced). If there is little or no effervescence, this usually indicates a soil with little organic matter and poor microbial activity.

 

Established value Characteristics Estimated value
1 Very little effervescence after application of water peroxide
5 Light to medium effervescence
10 Abundant effervescence 

Indicators of Crop Health

 

All tests below will be simply be performed by visually examining your crops.

Appearance of Crops

Established value Characteristics Estimated value
1 Chlorotic, discolored foliage with deficiency signs
5 Light green foliage with some discoloring
10 Dark green foliage, no signs of deficiency

 

Crop growth

Established value Characteristics Estimated value
1 Uneven stand, short and thin branches, limited new growth.
5 Denser but not uniform stand. Thicker branches, some new growth
10 Abundant branches and foliage. Vigorous growth

 

Disease incidence

Established value Characteristics Estimated value
1 Susceptible, more than 50% of plants with damaged leaves and/or fruits
5 Between 20-45% plants with damage
10 Resistant, less than 20% of plants with light damage

 

Insect pest incidence

Established value Characteristics Estimated value
1 More than 15 leafhopper nymphs per leaf, or more than 85% damaged leaves
5 Between 5-14 nymphs per leaf, or 30-40% damaged leaves
10 Less than 5 nymphs per leaf, less than 30% damaged leaves

  

Natural enemy abundance and diversity

Established value Characteristics Estimated value
1 No presence of predators/parasitic wasps detected in 50 ramdom leaves sampled
5 At least one individual of one or two beneficial species
10 More than 2 individuals of one or two beneficial species

 

Weed competition and pressure

Established value Characteristics Estimated value
1 Crops stressed, overwhelmed by weeds
5 Medium presence of weeds, some level of competition
10 Vigorous crop, overcomes weeds

 

Actual or potential yield

Established value Characteristics Estimated value
1 Low in relation to local average
5 Medium, acceptable
10 Good or high

 

Diversity of Vegetation

Established value Characteristics Estimated value
1 Monoculture
5 A few weeds present or uneven cover crop
10 With dense cover crop or weedy background

 

Natural surrounding vegetation

Established value Characteristics Estimated value
1 Surrounded by other crops, no natural vegetation
5 Adjacent to natural vegetation at least on one side
10 Surrounded by natural vegetation on at least two sides

 

Management system

Established value Characteristics Estimated value
1 Conventional
5 In transition to organic with IPM or input substitution
10 Organic, diversified with low external biological inputs

 

Use the drawing below, chart your Amoeba graph for Soil Quality

 

(SEE DOWNLOAD)

Repeat the process about for your Amoeba for Crop Health

(SEE DOWNLOAD)

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