Hannah Francis, a US Fulbright Student Grantee in El Salvador, recently opened my eyes to the magnificent universe of Salvadoran dirt. Her knowledge ultimately concerns how our food is grown and what chemicals we manipulate in the environment to grow it. What she has to say is important for those of us who think about farming and ecology in El Salvador.

Mike: Hannah, while we’ve already talked quite a bit about soil science, I like that you say that farmers are the first experimenters.  Can you tell me more about that?

Hannah: While farmers may not be creating smoking reactions in sterile lab environments, their experimentation is “organic”. Farmers are willing to try out new practices they have seen in action, like intercropping or leaving plant residues for soil cover. The other day I was in the field with a farmer who mentioned that his neighbors come by and take some seeds from a bean plant with them. His neighbors saw that his corn was growing really well intercropped with this bean plant. Similarly, another farmer spoke of a neighbor up the hill who has a great plant, called zacate, in a variety he hadn’t seen before, and went to go get some samples to bring to his farm.  They will try new fertilizers and dabble in organic agriculture. These farmers care for their plot of land, and they have an innate sense of the soil-air-water interface that I can’t have by just looking at soil chemistry data.

So, while farmers might not be conducting rigorous, controlled, scientific studies, this doesn’t exempt them from the title of experimenter. Instead, farmers operate in a dimension of elegant trial and error that is constant experimentation. The experimentation, however, does need explanation, and that is where I think the present-day Salvadorian farmer is generally lacking. The “why does this crop work better, or why does soil cover give me a higher yield” is not quite there for many Salvadorian farmers I have interacted with, but is the critical next step.

Mike: I often find myself in conversations with farmers where we are making conjectures about what is happening in the soil itself.  Sometimes we manipulate the soil with organic or synthetic fertilizers, without fully understanding what is happening in the dirt. I understand that this is where you have expertise. How do you even get to the point of knowing what is in your soil, and why is that important?

Hannah: In plants, there are basic things that come naturally in the soil, or that are added in fertilizer.

So, how do we even know what our soil needs? And how do we know what we’re adding when we apply fertilizer?

In the soil, there are three main nutrients of concern that are usually in deficiencies: Nitrogen, Phosphorous, and Potassium (N-P-K). Most major fertilizers are made up of these three elements—the heft of the food for plants. When you look at a fertilizer, instead of NPK, you usually see numbers. In El Salvador, this can be 16-20-0, which means there is 16% nitrogen, 20% phosphorous, and 0% potassium to 15-15-15 to 18-46-0 (each number a corresponding percent of N, P, or K).

A commercially available fertilizer in El Salvador. It contains phosphorous, potassium, and nitrogen

When you apply a fertilizer like 15-15-15 without knowing what your soils needs, or exactly how hungry or what craving it has, it’s like us humans not being hungry and throwing away food that is offered to us. When a plant is in a soil that has sufficient, say, potassium, and you add even more potassium, that extra amount won’t do anything extra for the plant, and it goes unused. That happens often—a soil will have sufficient potassium and the farmer will go an add 15-15-15, which has 15% potassium, but very little phosphorous, which might actually be deficient in the soil. While plants can express nutrient deficiencies in a variety of ways, soil testing is another great way to tell if your soil is deficient in one thing or another.

Mike: Tell me more about testing soil.

Hannah: When you take a sample of soil around the farm plot (usually a variety of locations, clearing the top of leaves, sticks, etc, and 0-10 or 0-20cm deep), you compile the sample and bring it to a soils lab. The lab will do a variety of analysis, and give back a report that tells you what quantity of which elements are in the soil. From there, the lab will often give recommendations of quantity and type of fertilizer to apply, but it is always good to double-check, as sometimes these recommendations are generic rather than based in calculation. Different soils should be considered differently too.

A soil sample brought to the CENTA laboratory (Centro Nacional de Tecnologia Agropecuaria y Forestal) in El Salvador

Mike: So understanding what your soil specifically needs is preferable to simply applying fertilizer that is found in the store?

Hannah: Specific application of fertilizers is much more likely to increase yield than random application of fertilizer, which is like throwing away good food.

Mike: Speaking of yield, I want to talk a bit with you about corn  – a major staple crop here in El Salvador. Archaeologists have found jade carvings in Mesoamerica, some 1500 years old, showing corn sprouting from peoples’ heads. But the history of corn goes back much further than that, doesn’t it?

Hannah: I can look back 10,000 years, about when history shows agriculturalists branching from the hunter-gatherers. These farmers, especially in Meso and South America, planted varieties of corn for years, selecting and [genetically] modifying corn to its present-day yellow cob. And these farmers did this for thousands of years—it’s engrained in farming genetics to “if at first you don’t succeed, try, try again”.

Mike: I understand that something that arose from trial and error was the “three sisters” method, where corn is intercropped with beans and squash.  This practice made it all the way up to the Iroquois in Canada, and I still see it being used among some farmers here in El Salvador today.  From your perspective, why do you think the three sisters method has survived the test of time?

Hannah: We’re actually re-teaching this method even today. Corns, beans, and squash make for a yummy meal, but the beans, planted alongside the corn, provide soil cover and fix nitrogen. They take nitrogen gas from the atmosphere and convert it to nitrogen that is usable for plants, which is a very important nutrient, and their big leaves cover the soil, maintaining soil humidity by providing a physical barrier from the sun. This means there is more water available for the plants over a longer period of time. The squash plants protect the soil in a similar way. All plant material from one cycle left on the soil is cycled as soil organic matter, providing even more nutrients for the next cycle of crops.

Ash that one farmer mixed with ammonium sulfate, phosphorous, nitrogen, and potassium for the second fertilization of his maiz blanco (“white corn”)

Mike: Another farming practice that I have observed in El Salvador is the “slash and burn” method, where fire is used to clear a milpa or a forest before cultivating it. Can you tell me about the advantages, disadvantages, and alternatives to “slash and burn” techniques?

Hannah: As I understand it, burning takes precious organic material left on the farm and converts it to a nutrient dense ash. However, on farms that are left bare, without permanent vegetation or even annual crops, the ash is usually eroded by wind or water. That ash is then useless, because it is no longer on the farm, and the farmer has now lost a wealth of potential free nutrients for their plants, lost soil cover, and actually decreased the soil health. In addition to direct loss of nutrients, burning can kill micro and macro invertebrates that are key in nutrient cycling and in maintaining a healthy soil structure. Burning can also create a hard water-repellant upper layer on the soil at certain temperatures (this has to do with how some hydrophobic molecules move around), compounded by the loss of bugs in the soil that would otherwise facilitate a porous structure.

As an alternative, I’ve heard about this technique called “biochar”, though I’m no expert. As I understand, it involves burning organic matter very slowly to create nutrient dense charcoal that is then added to the farm.

Mike: Beyond deep historical practices reaching into the present, what are some of the ways in which the Salvadoran Civil war impacted the quality of soil that farmers are dealing with today?

Hannah: This story is more complicated than I could ever put into concise wording, and I’m sure I’m missing parts of the story. However, here is my best brief grappling with the effects of social discords and soil health. First, there were a few uprisings related to land reform—the first one in 1930 and the second in 1980. The first attempt at land reform was squashed, however, people began realizing that land was in the hands of very few, very wealthy landowners. This realization coupled with politics at the time led to the land reform in 1980, where the agrarian reform took land from the wealthy and spread it to create equal opportunity for the “poor”. At the same time, El Salvador began a harrowing civil war that lasted 12 years from 1980-1992. Not only were land parcels nearly too small to farm for the new land owners, but areas in the country became dangerous and land was abandoned. Since the land was abandoned, it went unmanaged, which we might imagine could be a good thing, but previous use of herbicides, fertilizers, and pesticides meant that some land relied on management for soil fertility. Following the Peace Accords, the focus was on urban employment, and farmers were not recipients of any favors. So, even after the agrarian reform, most farmers rent their land. Renters have little incentive to invest in long-term change (like planting trees, terracing, etc.) when they only work their field for 2 years, maximum.

Mike: Hannah, how did you come to know so much about soil, the environment, and farming?

Hannah: I still have so much more to learn about the soil, and I was a total newbie about agriculture when I got to El Salvador, although I got a little primer in soils 101. But, I guess I just ask a lot of questions, and try and connect the different answers I get. I will say for sure that I am always eager to learn more.