Farming. He describes how during the 1800s, farmers look for nitrates, and moving away from traditional methods such as field rotation. This class is about 50 minutes. My name is paul. I am a professor. I want to welcome cspan viewers to our history class. This is an environmental history focus. And today, our history is on agriculture and the fertilizer revolution. We began this course talking about agriculture and the frontier the expansion of the agricultural frontier across the world. And the birth of the plantation complex in tropical regions. But another critical storyline of the last few hundred years has been agricultural intensification. The growing, getting more crops out of those. And this coincides with the industrial revolution. In thereated a real need europe and United States to really concentrate on food ,roduction to escape the trap this notion that population would grow faster than to production. We were talking about something called the green revolution. Where a lot of modern industrial agriculture was spread to the rest of the developing world. But today, i want to talk about the 19th century. What im going to call the fertilizer revolution. And in the most general sense, a shift away from closed systems of agriculture, where fertility was raised in the farm. And we will talk about that. In whichn system forms of soil fertility were imported into the farm. They were mined and brought out to the farms, used intensively, and would pull nutrients off the farm, out of soils, and away from the land. This became an open system of Nutrient Cycling. And i want to use this term metabolic rift. A sociologist going to this term also from karl marx. By metabolic rift i mean a break in the chain of Nutrient Cycling first on the farm and then between the city and the countryside. With traditional sources of fertilizer becoming waste and new sources of fertilizer needed. What we will see then is the sense of industrialization of soil fertility. The transnational story, i will tell it that way, with a focus on the United States. Ok . Before talking about that, lets step back for a minute and look at what soil and soil fertility is. Soil is one of the most important natural resources. Obviously. It is basically the result of several processes. The first is simply the breakdown of what is called parent material like rock and sediment into loose matter that provides minerals for plants to grow. The second is the breakdown of organic material which combines with this broken down parent material and gives soil its physical, neural structure. And biological structure. And finally, recognize soil as a living thing. There are all sorts of insects, worms, microorganisms at work in soil that are critical to plants and crops growth. In other words, soil characteristics are biological, physical, and chemical. Now, plants need all sorts of things to grow, it is pretty basic. They need sun, water, carbon dioxide. But they also need nutrients, macronutrients in particular, like nitrogen, phosphorus, and potassium, the holy trinity of effective fertilization. And they also need micronutrients, we wont talk about those as much today. Most macronutrients come from the breakdown of soil, but the most troubling one would be nitrogen. That is at the heart of todays story. Ok . Lets talk about the nitrogen cycle, i know this is a history class, but it turns out it undergoes a dramatic historical change during this period. So, what is the nitrogen cycle . It is a cycle of nitrogen between land and atmosphere. This is worked out largely in the 19th century. Before that, people did not fully understand the nitrogen cycle. But we now know the atmosphere itself is about 79 nitrogen. And that atmospheric nitrogen is a critical source of nitrogen for plants and plant growth. But it is not immediately available to plants. And this is the most critical point we have to make, it is locked up in this n2 at him. Plants cannot break it down. They cannot breathe nitrogen, so it has to be made bioavailable to them. I think we talked a little bit about this before. One is a lightning, which can fix nitrogen in the soil, that is an unimportant part of the cycle, but worth knowing. The other two ways are by soil microorganisms. Some of which are symbiotic with a type of plant called a legume. They live on the roots of legumes. They have the capacity to pull nitrogen out of the atmosphere and put it in the soil in ways that make it available to plants. To the planting of leguminous plants like peas, soybeans, peanuts, blackeyed peas, lentils, these were all crops that have the capacity to fix nitrogen from the atmosphere into the soil. There are also nonsymbiotic bacteria that can do this, as well. But those legumes are really critical. The earth has a natural nitrogen cycle, nitrogen is constantly cycling in the atmosphere and in the soil. It is a result of decomposers, taking bacteria, and even denitrifying bacteria. Bunnies apparently help in this process. [laughter] so, that is the nitrogen cycle. And what i want to emphasize, one of the products of the metabolic rift i referred to, is the human transformation of the nitrogen cycle into the 20th century. That may not make a lot of sense to you right now, but i promise i will get to it and explain it in some detail. But were getting ahead of ourselves. So, lets talk about the critical problem here, how do farmers over time maintain soil fertility on the lands they are farming . And before we get to this fertilizer revolution, i want to suggest a of ways in which they did that. Perhaps the most important, early on, was shifting cultivation. By shifting cultivation, the dominant mode of fertilizer management worldwide. It was an approach whereby farmers would clear it a piece of land, usually for us, usually using fire to burn off and make nutrients from organic material immediately available. It turned out that the fire and the ash produced has a basic ph which could correct for acidic soil. Farmers would then farm that cleared land for a certain period of time, taking advantage of the natural fertility in the soil. And when that land stopped producing crops, when the fertility began to wane, farmers would move on and clear a new piece of forest and let the old field revert back. They might come back around to it, but decades later when it had regrown back up and restored its capacity to be fertile as a result of that regrowth. Now, practice on a small scale, shifting cultivation, was reasonably sustainable, and not that damaging, ecologically. Though it was and still is a landintensive way of farming. It required a lot of land. Maybe another way to think of it, for the little piece being farmed at any moment, there has to be a lot of land available so the farmer can then migrate. Does that make sense . Ok, so that was one of the most important ways in which farmers managed soil fertility in the past. And typically in tropical regions. We will talk about why that is the case in later lectures. But it turns out tropical soils, burning is a good match for them. Ok, now, having focused on slash and burn as a strategy, a tremendous number of American Farmers also practice this, particularly true in the American South. That part of the United States where plantation crops were grown like tobacco and cotton. Farmers would farm the land until its productivity was worn out, and then they would move on. And this actually created a caricature of the southern farmer as a soilminer. Someone who did not care for the land, went out and cleared the land, took the nutrients out of course, they were growing staple crops like tobacco and cotton they would mine the soil nutrients and then move on. And so, a lot of agricultural farmers and others who valued the stable, sedentary agriculture saw this as a particularly slovenly or wasteful they would not say environmentally destructive, but that is what they meant. There was an attachment in places like the American South to being more settled and civilized. And this brand of agriculture seemed messy. It actually seemed a lot like native american agriculture. They practiced slash and burn cultivation for the most part. The other thing southern farmers also did was practice a variation on this called forest fallow. A farmer might own thousands of acres of land, but only farmed a couple of Hundred Acres at a time. That farm base was there so they could cycle their arable land through the entirety of that plantation over may be a 20 or 30 year cycle. It did not look good, but it was potentially sustainable. And of course, this land use and soil fertility management system, combined with slavery in in particular ways in the south, southern farmers were particularly interested in maximizing their investment in slaves. And to do that, they had to get as much productivity out of the land as possible. In the context where there was a lot of land to be had, and there was not a lot of labor to be had. So, there was an economic logic rooted in slavery to the upon shiftingnce cultivation of the Strategy First soil fertility management. Ok, clear so far . Questions from anyone . If not, i will charge more to the interesting stuff. It is yet to come. Another way of managing soil fertility, i will mention this quickly and move to another system. It is to manure. Manure,use the word what do usually think of, when you hear the word manure . Animal manure. It can mean a variety of things. I include fallowing here, you would farm a field for a while and let it rest. Letting it rest would return some fertility. Probably not enough for agriculture to be sustainable. But a lot of farmers required ground manure. But also nightsoil, and human waste. Also, organic materials near the ocean, seaweed, leaves from the forest. Also, the use of cover crops and legumes, sometimes plowed into the land. All of these were important to return nitrogen and other macronutrients to the soil. But there were two things about them farmers did not always love. One was that they were laborintensive. If shifting was laborintensive, applying manure was, too. And it did not allow for the maximization of one land for commercial production. That is an important point. Ok, we will feel that works in a minute. It did allow for agriculture to be a more landindeterminate thing. Ok, with this model of soil fertility management, we see in Great Britain across the 17th and 18th centuries, and emerging revolution that allowed for much more intensive agriculture on a fixed pieces of land, sustainable over the longterm. I will explain this quickly, it is complicated. But what it involves replacing fallowed land, land out of production, replacing it with a sort of rotation through the farm of improved pasture. With particularly good pasture grasses, some of which were legumious. They were used for human and animal consumption, and grain and other marketable crops. And then pasture. The idea is that youre devoting a substantial part of your form to growing things the animals are going to eat. And that animal digestive process will produce a really high quality manure. Especially if youre using turnips. Farmers became very careful stewards of this manure, dung, as they called it. It allowed them, effectively, to within the bounds of a permanent, settled farm, raised sufficient soil fertility as livestock manure to keep those farms producing indefinitely. And they would move past years to farmland to clover, and rotated through the farm, so the nitrogenfixing of the clover would be used for grain farming later on. Ok, this was a very effective system, called convertible husbandry. Sometimes called the norfolk system. And it managed to retain soil fertility really effectively. But it was incredibly laborintensive. And it meant that only a small portion of one plant at any given time could produce crops for market. And for those reasons there is actually a reform in the American South of that tried to get southern farmers and planters to raise more livestock res, and to pastu produce highquality manure in a way that would allow them to settle in place, and not be constantly engaging in shifting. It did not work, because they were more interested in using fresh land to produce big crops of tobacco and cotton and to maximize their capacity to market these crops. Particularly, if they had investment in slate labor. Ok. Nonetheless, this was a really important, and pretty powerful way, of raising soil fertility in a closed system. Be the, this came to best model of the western world for a closed system for fertility maintenance. Make sense . Ok. Now, we will look at how the system gets cracked open. Before doing that, i want to take a quick digression, and that is what happens to fertility management as people urbanized more and more. Because as more and more people are concentrated in urban areas, urban areas themselves become places that have a lot of organic nutrients that need recycling. And that happens in a variety of ways. One, this might be from Great Britain, a figure known as the rag and bone man, they would go around to household and collect any rags that people might have, or bones, as a result of cooking or slaughtering livestock. Or whatever. Do you know what the rags were used for . Any idea . The rags were the critical resource for papermaking in the 19th century. So, papermaking relied upon rag recycling, but the bones were used for fertilizer. And so, these folks would aggregate huge collections of rags and bones. This is a photograph from baltimore, a figure called the nightsoil man. And he would go around and collect human waste. This was before there was indoor plumbing, so all of these wastes were collected in privies. Right . You cannot photograph the smell. It was, perhaps not surprisingly, that this is an africanamerican worker. This worker would collect the wastes and take them to the countryside. I will show you that in a minute. Do you know what that is . Any guess . Raise your hand. Gets to you. Til he this is a street scene in lower manhattan. This is horse manure, one of the greatest sources of fertility. And all of these things, nightsoil, bones, horse manure, would be brought out into the immediate hinterlands, and be dumped on the farmlands. Places like long island, brooklyn, queens, those were agricultural hinterlands in new yorks early history. They would produce a lot of crops for urban consumption. And they would get the urban waste recycled back to their land. Not a metabolic rift. Alright, but lets move in that direction. Oh, one last thing. Anyone know what this is a picture of . Zach american bison. Prof. Sutter yes. These are bison bones. People hunted bisons on the American Plains almost to extinction. When the bison were all but gone, commercially extinct, the next industry that hit the great plains was an industry to collect bones, which were then ground up into fertilizer. Yes, the question . Stuart is the bison species extinct . Prof. Sutter no, it is not. But it was the subject of intense market hunting. And they got to the point where there were so few left, there was a growing Conservation Movement to keep them from going extinct. And now they made a big comeback, although a lot of the bison we see, are crossed with cattle, so they are beefalos. There is a genetic mix there. That gives you a sense of how w important bones were to the fertilizer trade. Well, a quick scientific foray. Here, soil science is also critical to the story. And i wont bore you with too many details. But coming into the 19th century, scientists believed in the humus theory of soil fertility, the idea that it was fertile because of the organic matter and manures that were put on the soil and event breakdown into it. This is a model of soil fertility that i think anyone is spent time doing organic farming would be familiar with. It sort of made a bit of a return. But this man, a german chemist, challenged this and opted instead for a reductive soil chemistry that began to argue that fertile soils relied upon a couple critical nutrients. And again, nitrogen, potassium, phosphorus. Npk, that triad. If you go to any fertilizer store, there will be a three number ratio, the ratio of those three elements. He is one of the ones that encourages us to think of fertilizer as more like vitamins then food. The humus theory saw soil as something that needed to be fed. Liebig says no. An infusion of these chemical, mineral elements. Nitrogen would be the trickiest one. But as luck would have it, just as liebig was writing his major treatise on the subject in 1840, an industry was beginning to capitalize on a remarkable new sort of concentrated, mineable, nitrogen, that came from an unlikely, remote place. These islands, called the Chincha Islands. So, let me tell you a little about the Chincha Islands. Anyone know where these islands are . Nate . Hold on. Yeah, i was about to ask where these islands are located . [laughter] prof. Sutter anyone know . Theyre located off the coast of peru. Prof. Sutter i will show you a map later. It is a very small island, three of them granite, off the coast of southwest peru. That were best known as hosts for massive colonies of sea birds, cormorants, pelicans, who would come to these islands, and had been for hundreds of not thousands of years, urinating and defecating on these islands in huge numbers. Now, and i have to give you a sense of the magnitude of this because it is actually quite staggering. In some places, and we will see some pictures, people who came to mine these deposits found them to be about 150 feet deep in some places. Right . Now, how could this be . A couple things important about the ecology of these islands, there was the humboldt current that brought nutrients out of the deep sea water and up to the surface, which fed small fish, in this case, anchovies. Huge schools of anchovies around this area, which allowed the sea birds to feed without abandon on them. And they process this fish fertilizer throughout their digestive tract. Now, these islands also exist in a rain shadow from the andean mountains. And the result is that they get about one inch of rain fall a year. And why is that important . Skyler, hold on. Skyler no rain shadow means there was no chance to wash it away so there is no carbon. Family show. In this case, the lack of rainfall effectively means there is no washing away or leaching of this. In most other places, bird guano wouldve been washed away or leached away. These are almost pure, geological deposits of bird crap. Alright . They were used by peruvian native people for hundreds of not thousands of years. Russian great p nationalist humboldt asked, when he made note of these deposits and took peruvian quando back to him with europe where he had chemists test it and found it was incredibly rich in nitrogen. The first deposit to the United States, by o