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This is interesting to me. For the past 15 years I have had a small plot in the tropics on which I have tried to improve the soil by adding copious amounts of c

This is interesting to me. For the past 15 years I have had a small plot in the tropics on which I have tried to improve the soil by adding copious amounts of compost, manures and growing cover crops that I till under. All that organic material just seems to disappear quickly. Before I owned it the plot was planted with corn and sugar cane each year and lots of chemical fertilizers and pesticides were used. So the soil was ruined. I thought I could bring it back within a few years but it is still rather poor. There was one patch that looked much better after a giant pile of scrap wood left over from house construction was burned and the left over ash and char was plowed in. But that did not last long. It is all back to hard crusty soil now. The pH is rather high due to the high percentage of karst in the region and the high calcium carbonate content of ground water that is used to irrigate. Maybe that has something to do with it?

jbotz 5y ago
I think your experience is just normal for the tropics, and it has nothing to do with the specifics of your soil. Certainly I and lots of others have had similar experiences. In natural tropical environments the nutrients aren't in the soil, they are almost all tied up in the living biomass, and as soon as some of that dies the nutrients it releases are absorbed by other living vegetation. And generally, if we want to do things in a way that's sustainable, we should look to nature and try to imitate it (and once we can manage that, try to improve on it). What I've found is that the only way of doing tropical agriculture that's remotely sustainable is "slash and drop" agroforestry, which is where you interplant (a lot of) biomass for mulching together with your crop plants and keep cutting/pruning that to produce mulch, so that you can keep your crop plants heavily mulched all the time. This is fairly labor intensive, though, and worse, it requires highly knowledgeable labor to maintain.
- geomark 5y ago
  That is very interesting. What are the preferred plants to grow to produce the biomass for slashing and dropping?
  - jbotz 5y ago
    There are too many to list, and it depends entirely on the crop system you're trying to support. For example, for annual crops it would be different than for multi-year agroforestry systems, and you may want some plants to provide windbreak or shade for others at an early stage, and then remove them when others are more mature, etc. Also, you want a mix including some legumes for their nitrogen fixing ability. And some plants are better at utilizing and accumulating specific minerals (bioaccumulators), so may want some of those. In short, it's complex and requires a good deal of knowledge or willingness to experiment, which is why it's not more widely practiced, even though when done correctly it undoubtedly is very effective, sustainable, and requires far fewer inputs than any other agricultural practices. At least in theory, a master of this art can design systems that are planted once and the produce different crops for several years while mimicking the natural succession of a grasslands in transition to becoming a forest with a fairly small amount of maintenance (harvesting crops at different stages and chop-and-drop'ing mulch plants). One master of this art here in Brazil, whom I've learned a lot from, is Ernest Götsch[0][1]. [0] https://agendagotsch.com/en/ https://agendagotsch.com/en/ [1] https://en.wikipedia.org/wiki/Ernst_Gotsch https://en.wikipedia.org/wiki/Ernst_Gotsch

jbotz 5y ago

I think your experience is just normal for the tropics, and it has nothing to do with the specifics of your soil. Certainly I and lots of others have had similar experiences. In natural tropical environments the nutrients aren't in the soil, they are almost all tied up in the living biomass, and as soon as some of that dies the nutrients it releases are absorbed by other living vegetation. And generally, if we want to do things in a way that's sustainable, we should look to nature and try to imitate it (and once we can manage that, try to improve on it). What I've found is that the only way of doing tropical agriculture that's remotely sustainable is "slash and drop" agroforestry, which is where you interplant (a lot of) biomass for mulching together with your crop plants and keep cutting/pruning that to produce mulch, so that you can keep your crop plants heavily mulched all the time. This is fairly labor intensive, though, and worse, it requires highly knowledgeable labor to maintain.

geomark 5y ago
That is very interesting. What are the preferred plants to grow to produce the biomass for slashing and dropping?
- jbotz 5y ago
  There are too many to list, and it depends entirely on the crop system you're trying to support. For example, for annual crops it would be different than for multi-year agroforestry systems, and you may want some plants to provide windbreak or shade for others at an early stage, and then remove them when others are more mature, etc. Also, you want a mix including some legumes for their nitrogen fixing ability. And some plants are better at utilizing and accumulating specific minerals (bioaccumulators), so may want some of those. In short, it's complex and requires a good deal of knowledge or willingness to experiment, which is why it's not more widely practiced, even though when done correctly it undoubtedly is very effective, sustainable, and requires far fewer inputs than any other agricultural practices. At least in theory, a master of this art can design systems that are planted once and the produce different crops for several years while mimicking the natural succession of a grasslands in transition to becoming a forest with a fairly small amount of maintenance (harvesting crops at different stages and chop-and-drop'ing mulch plants). One master of this art here in Brazil, whom I've learned a lot from, is Ernest Götsch[0][1]. [0] https://agendagotsch.com/en/ https://agendagotsch.com/en/ [1] https://en.wikipedia.org/wiki/Ernst_Gotsch https://en.wikipedia.org/wiki/Ernst_Gotsch