Discussions regarding soil macroflora and -fauna sampling
(8/19/01 - 9/6/01)

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postings: 6
countries: Nicaragua, Viet Nam, Zambia, Ecuador, Australia, South Africa,
organizations/institutions/companies: CATIE, CIDSE, Eco-Suelos, Forestry Support, Rand Water

Date: Sun, 19 Aug 2001
To: MULCH-L@cornell.edu
From: Chuck Staver
Subject: soil macro flora and fauna

Mulchers,

We are developing a methods proposal for baseline sampling of soil macro flora and fauna for a long term experiment on coffee systems under different trees. We need some simple, low cost methods which will be specific enough that we will be able to measure response to different types of associated trees and different fertility regimes (high and medium chemical fertilizer and medium and low organic amendments). Any suggestions on methods and bibiliography??

Chuck Staver
MIP-CATIE
Nicaragua

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From: Mike Zeiss
To: MULCH-L@cornell.edu
Subject: Re: soil macro flora and fauna
Date: Mon, 20 Aug 2001

Dear Chuck,

While at Zamorano (Honduras), I worked as part of an interdisciplinary team on "soil health". Like you, we were trying to develop simple biotic indicators that farmers could use to "prove" that soil was healthier when sustainable production practices were used.

First, I want to say that it proved to be very difficult! I know that you are an excellent ecologist, so the following comments probably won't tell you anything new. But I want to make sure that you are forewarned! I was much more optimistic then than I am now.

One difficulty is, the abundance and diversity of soil biota is very heterogeneous, certainly among fields but even within a given field. At the very least, you will want to have carefully-matched pairs of coffee fields (or plots within the same coffee field) in which to contrast your various combinations of trees and amendments. Otherwise, soil type and previous management history may "swamp" any effect of your treatments. Also, be sure to take lots and lots of samples! To conserve resources, probably best to mix together some samples and then conduct your test on an aliquot drawn from the mixed samples.

A second difficulty is that, once soil chemical and physical quality is above some minimum threshold, additional improvements in soil quality may not have easily-measured effects on soil biota. Put in a bit of organic matter, make sure that pesticides and fertilizers are not at toxic levels, and that may be enough for most soil organisms. Indeed, several soil ecologists warned me at the start that it simply was misguided to think that the abundance of any species would be a reliable indicator of (for example) the impact of organic amendments. Probably it is not a coincidence that Soil Science Society of America, in developing its soil-health test kit for farmers, concentrated on more integrative tests (for example, burying pieces of filter paper to quantify the overall activity of the entire guild of decomposers).

Probably due to both difficulties, a Cornell MPS student (Matt Thornton) working with me at Zamorano failed to detect consistent differences among common agricultural practices (cover crops versus herbicide use, conventional tillage versus no-till, etc.) in maize. The indicators that he used included:

1) Abundance and diversity of mesofauna (earthworms and arthropods) 2) Gross colony morphology of fungi, actinomycetes, and bacteria cultured on 3 semi-selective media 3) Root disease symptoms on susceptible cultivars of lettuce, green bean, and tomato seeded into pots of the field soils 4) Abundance of nematode guilds (external feeders on plant roots, internal feeders, and free-living nematodes) 5) Water infiltration rate (abiotic, but can be linked to soil organisms)

So: think carefully before heading down the same road!

An alternative to measuring the organisms themselves is to measure something that is correlated with them. I already mentioned the example of burying filter paper to quantify biological activity (decomposition rates). Another example (and some would say by far the best option) is to measure the active carbon fraction. "Active" carbon is biologically available (stuff like bacterial cell walls). It can be quantified by a relatively simple colorimetric laboratory test. I will copy this message to Melissa Stine, who while a M.S. student with Dr. Ray Weil at University of Maryland, did her thesis research on correlating active carbon with previous agricultural practices and subsequent maize yield in Honduras. Melissa, please send Chuck some citations.

Okay, having tried my best to discourage you, my suggestions about sampling the flora and fauna themselves are:

1) In Honduras and Nicaragua, among the techniques that we tried, the farmers' favorite techniques were:

a. Sieving samples of soil onto a big piece of yellow plastic, then manually searching for mesofauna. We used simple wooden-fram sieves, passing the soil first through 1/4 inch mesh hardware cloth, then through standard window screening. Yellow plastic makes it easier to spot the many mesofauna that are colored white. Farmers were fascinated to see the diverse critters; they had never imagined their soil was so alive. Overall abundance is much higher under a cover crop; it's a great teaching tool, but not sure how well it would serve you as a quantitative indicator.

b. Filling flower pots with samples of field soil, then planting seeds of susceptible cultivars into the pots. Water the pots as needed. Once the seedlings have a few true leaves, wash the soil away from the roots and rate the roots for lesions, root-knots, and overall vigor. Lettuce is susceptible to most everything. Green ("French") beans are susceptible to Meloidogyne and many other pathogens. Tomato is particularly susceptible to Phytophthora. This test was developed for us by George Abawi at Cornell.

2) Look at the "soil health" special issue of Applied Soil Ecology (Volume 15 Number 1, August 2000.) Most of the articles contain many helpful suggestions about sampling methodologies. Note that Applied Soil Ecology has a website:

http://www.elsevier.nl/locate/apsoil

And the article by John Doran (with me as co-author) cites many additional useful references. In particular, I strongly recommend the book on biotic indicators published by CAB International:

Pankhurst et al. 1997. Biological Indicators of Soil Health. CAB International, Wllingford.

3) The SSSA soil-health test kit is a good place to start. Check the citation in Michelle Wander and Laurie Drinkwater's article within the Applied Soil Ecology special issue mentioned above. Their article includes a very useful table of "hands-on soil quality activities and demonstrations". The citation that they give for the Soil Test Kit is:
Sarrantonio et al. 1996. On-farm assessment of soil quality and health. In: Doran and Jones (eds.), Methods for Assessing Soil Quality. SSSA Special Publication No. 49. Soil Science Society of America, Madison, WI, pp. 83-107.

Or, see a photograph at:

http://www.uvm.edu/~nesare/slides/sld023.htm

4) For a nice package of training materials and sampling methodologies suitable for campesinos, see Bill Settle's "living soils" documents on the FAO IPM website:

http://www.communityipm.org/living%20soils.html

Okay, Chuck, hope this is helpful. Best of luck, and best regards,

Mike Zeiss
Agriculture Advisor
CIDSE / Viet Nam

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From: Gail Andrews
To: MULCH-L@cornell.edu
Subject: RE: soil macro flora and fauna
Date: Mon, 20 Aug 2001

Chuck Staver,

In response to your "Mulchers", section:
" We are developing a methods proposal for baseline sampling of soil macro flora and fauna"

I have a trial running in South Africa. I have used as mulches 3 x grass, 3 x pine bark ,3 x garden refuge chopped up and 3x bare soil. They have been established with and without plants. The aim of the trail was to pin point the water saving using mulch. I also did one comprehensive dip stick soil sampling including invert ( microbial activity) counts every 10cm to a depth of 30cm in each of the 12 plots. There was a marked improvement in the mulched plots, particularly the grass plot. I am due to sample again in a months time. I would be happy to share these finding with you. I would also be grateful for any inf. that you might have on the topic. It was a side line interest at the time when I looked at it but I love to know what every one else has found.

While I am on this topic of water saving using mulch it appears a rather controversial issue. I find and many others people who have done similar work, that the soil is more moist under the mulch. But the water saving issue appears more illusive. Plants appear to use water in the same proportions with and without the mulch. Mulched (with and without plants) and unmulched (with and without plants) plots show very similar rates of depletions. The mulch does not seem to change the water use.

Some work I have read say that mulch causes the air above it to heat up and at times could cause plants to actually use more water.

Has any one actually been able to establish how to determine if mulch saves water or not other than the soil is more moist?

Gail Andrews
Rand Water
South Africa

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Date: Mon, 20 Aug 2001
To: MULCH-L@cornell.edu
From: Stephen G. Sherwood
Subject: Re: soil macro flora and fauna

Dear Chuck,

I am glad that Mike took the time to respond thoroughly to your question. Unfortunately, I am heading to the field, so need to be brief...

I agree with Mike's account of the experience in Honduras. I have been building on that work with the on-going Eco-Suelos project in Ecuador, part of a broader MOSANDES effort, that is looking at the impact of agriculture (rotations, tillage, etc.) on soil regenerative capacity. We are just beginning, but are using more sophisticated techniques than the previous experience that Mike described, in the hope of identifying patterns, at least if we look at the soil for a long enough period of time... Beyond standard physical and chemical indicators, we are including diverse biological factors, using pathogen bioassays (similar to Abawi's methods described below), micro and macro arthropod counts (will be using methods developed by Paul Voroney at Guelph; pvoroney@lrs.uoguelph.ca) and micro-morphology to quantify spaces and aggregation (methods developed by Richard Protz at Guelph; rprotz@lrs.uoguelph.ca). Richard and I once held discussions with farmers and extensionists in Ecuador over the resulting catscans digitalizing soil spaces following diverse soil management regimes; this was useful for presenting the importance of spaces and how agriculture can either conserve or destroy them. A group from Cuba is visiting next month to help us improve techniques for working with Mycorrhizae (Walter Bowen could provide further details, bowen@cip.org.ec). We will also be looking at indicator bacteria, nematodes and actinomycetes. You may want to look at SSSA Special Publications Number 35 (Defining Soil Quality and indicators) and 49 (Methods for Assessing Soil Quality), that can be found at its website.

I hope this is useful. Good luck!

Steve Sherwood
(Eco-Suelos, Ecuador?)

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Date: Tue, 21 Aug 2001
From: PAUL WOODS
To: MULCH-L@cornell.edu
Subject: Re: soil macro flora and fauna

Mike

Hi! I was surprised to find you on the mulch list. Hows the work going at CIDSE?

I have worked on soil quality - in relation to frequent burning. we were trying to show that frequent 'burning off' caused a run down in soil properties. We ran through all those problems you mentioned and ended up with a bio-assay technique. Basically we said that the quality of the soil is a function of its long term nutrient supplying capacity. Taking nitrogen as the prime element we developed an in-situ N mineralisation techniques that was very sensitive to management regime. It involved driving a tube into the soil, so fracturing the roots aand leaving it in place for a month. After removal you measure the levels of various N fractiions - ammonium and nitrate N at different depths in the sample (0 to 2.5 cm, 2.5 to 5 cm, 5 to 10 cm). It worked well. I can get some references to it from my old team members if you like.

Cheers,
Paul

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Date: Thu, 06 Sep 2001
To: MULCH-L@cornell.edu
From: Chuck Staver
Subject: macro and micro flora and fauna

Mulchers,

To all those who contributed to the discussion on soil macro and micro flora, thanks very much. the comments were extremely helpful. We still need to figure out what we are doing, but the experiences and references were invaluable.

Again Thanks!!!!

Chuck Staver
MIP-CATIE
Nicaragua