Healthy soil and sustainable growing

[Emery Mitchamore <emitch@att.net>]

Kinda begs the question: If everyone is vegan, where does the animal manure come from?

E. E. "Mitch" Mitchamore
www.hillcountrynatives.net

On Jun 5, 2010, at 3:01 PM, Ken Hargesheimer wrote:

I visited three farms on one of my trips to Honduras.

Date:	11/25/2002 9:12:29 AM Central Standard Time
From:	rolando@cosecha.sdnhon.org.hn
Reply-to:	MULCH-L@cornell.edu

 

Frankly, I would disagree strenuously with the general conclusion. Of course, in a sand, you're going to have a problem. But I have seen farmers build up soils to very high levels of productivity in thousands of cases, without using chemical fertilizers. 

 

OK, first of all, in the simple logical sense, you can't argue something is impossible just because you haven't seen it yourself.  That's how we got to the idea that you can't build up and maintain high levels of organic matter in tropical soils (now disproven) and grasses can't access N from legumes (it's now been shown that this very thing DOES happen, through micorrhyzae) and a whole raft of other mistakes having to do with soil dynamics. The problem with this reasoning is that we may have tried to WRONG way to do it, or even many wrong ways. (Such as growing clean-ploughed row crops for 40 years in India. Sure, if you try to do it THAT way, it's impossible!)

 

So how do farmers build up their soils? Well, of course, the first problem with this question is, what do we mean by "build up"? If our definition of to "build up" is based on the nutrient quantity theory, then by definition, we will need NPK. But NPK can, of course, be obtained in purchased chicken manure, purchased urban wastes, from a composting latrine, from incoming irrigation water, incoming water-borne soil, etc. Or even birds and bats. (And the quantities in the last case are more than a lot of people would ever dream.) So much for the argument that inorganic NPK is needed. Not even theoretically, using the nutrient quantity theory, is it necessary, unless you want to do it on a huge scale. I frankly don't see how anyone can say what I have just said is impossible--chicken manure (which thousands of farmers use here in Honduras every year) has all three nutrients, and in decent enough quantities to get very good yields. So the proposition that inorganic NPK is necessary to build soils is false. Period. In the theoretical sense.

 

But the above argument really only has value for theoreticians who don't care much about the real world. If we are going to be practical, we need to go a lot further than this. We need to ask: "Can poorer farmers increase substantially their productivity on initially very poor soils without spending any more than their increased yields would pay for, and can they do it with resources that would be available for the vast majority of poor farmers around the world? Now we're asking a question that has widespread developing nation applicability.  And, incidentally, this is precisely the question World Neighbors/Central America, COSECHA, and CIDICCO have been working on for the last 20 years (all of which I have been involved with).

 

My answer? YES. Resoundingly. In most cases. You don't believe me? Come visit us. I'll have my personnel take you to see any number of farmers you want, as long as the number's less than 5,000.

 

How?  Well, I can't go into it all that deeply here. (We do have papers on a lot of these subjects that are available.  For instance, I could get into issues like the nutrient access vs nutrient quantity theories, but I won't.  Let's just say that we use all sorts of tropical legumes, some trees, some viny or bushy or crawly. These are capable of fixing commonly from 75 to 150 kg N/ha/crop. They make the soil softer, more able to hold water, and increase the CEC (none of which chemical fertilizers can do). They decrease erosion, cover the soil much of the year, and eventually allow farmers to switch to zero tillage, which also improves soil fertility in at least half a dozen additional ways (none of which chemical fertilizer can do). They also buffer pH (while most chemical fertilizer used acidifies the soil, making most tropical soils worse.) And they defend plants significantly against a whole array of insects and diseases, from white grubs and striga to termites and the corn borer worm (which is, of course, endemic here in Honduras, but no longer a worry for our farmers). Chemical fertilizer's impact on these problems is arguable, but nowhere near as good as that of organic matter. 

 

But I said the interventions had to be economic. Well, the way we use green manure/cover crops is not the traditional way (plant monocropped, cut at flowering and bury). This system is neither economically attractive nor best for the soil, in most cases.  We use gm/cc's in such a way that the soil they are in has no opportunity cost (known to the farmers involved), that they are not generally buried, nor are they cut before maturity. We also use multi-purpose legumes: ones that can be eaten, preferably, or ones that can serve as fodder, major controllers of noxious weeds, or as income producers.

 

As a result, productivity of basic grains has gone from, say, 0.5 t/ha/year to 4.5 t/ha/year. Yes, with no chemical fertilizer use.

 

But now I can hear the eternal cry of, "What about the phosphorus?" Well, it isn't necessary for about the first 15 years, at least. (In northern Honduras farmers have been getting good yields for 40+ years with no phosphorus applications and there is STILL no response to phosphorus applications.  Why? Now this time, you got me. I can't explain that one, either.)

 

But allow me to admit that phosphorus IS necessary sooner or later, and that farmers shouldn't just mine it down to nothing. Fine. What do we do? We use some animal manure. Or we recommend superphosphate (farmers don't always use it, ergo the 5,000 farmers out there I can show you.) (Although I am NOT an organic farming advocate, I do believe strongly that many scientists have failed to understand its potential without ever becoming well-informed about it.) 

 

So, what about phosphorus? A die-hard organic person would have two possibilities. Phosphorus-accumulating plants would be one, but then we're back to robbing Peter to pay Paul--something not everyone can do.  Or mining our own soils.  So then we have rock phosphate.  But it doesn't work very well--the response of crops is way too small.  Once again, we're back with the "If I haven't seen it, it doesn't work" phenomenon.  In fact, if rock phosphate is applied to the MULCH instead of the soil, the response is dramatic--MUCH more than if chemical fertilizer is applied directly to acid soils.

 

In fact, after years of working with both, I feel the evidence says that if you were restricted to one or the other, organics will improve soil a lot faster and MUCH cheaper than will inorganics.   So at this point I rest my case. And invite comments.

 

Roland Bunch

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