Often in conversations about the benefits or problems with Organic agriculture, you hear a common refrain. Nitrogen is nitrogen is nitrogen, organic opponents proclaim, the plant doesn’t know if the nitrogen is synthetic or organic in origin, and it uses it just the same. This is said to make the case that it doesn’t really matter what kind of fertilizer you use, it’s all the same to the plant in the end. But this perspective is missing a big chunk of the picture. It is certainly true that a plant doesn’t know the difference between synthetic or organic nitrogen, but to say that means all nitrogen sources are exactly the same is straight up false. Agriculture, and gardening for that matter, is not just about the plant. And the plant is not the only thing that the applied nitrogen interacts with.
I submit, for your review, the following piece of evidence. This is a bit of a soil test result from Colorado State University. The test was run on soil coming from a suburban lawn in the Denver Metro Area that we went over in our Landscape Management Class. The soil in this particular yard had two issues it was facing, according to the report. It had issues with salinity, in other words, too much salt in the soil, and it also was low on nitrogen. The recommendation was to leach the salts from the soil by adding 6″ of water to the soil, and to fertilize with a specified amount of nitrogen. However, if you will draw your attention to the part at the bottom labeled “Additional Comments” …
It might be hard to see here, so I took the liberty of blowing it up for you …
When I saw this in class I immediately perked up. I knew from my soil sciences class two semesters ago that over fertilizing resulted in salty soil, but I assumed that was the case for both organic and inorganic fertilizers, after all, nitrogen is nitrogen is nitrogen, right? This suggests that this is not so. I asked my teacher for confirmation. “Does this mean that if you were to use an organic nitrogen source, such as blood meal, it would not contribute to the salinity problem?” He confirmed that that is, indeed, what it meant. This teacher is by no means an Organic or all-natural evangelist. Like all horticulturists, he would strongly advise against over fertilization, but he is not one to have an issue with going to buy a bag of synthetic nitrogen fertilizer to use at appropriate levels in his landscape. “So,” I concluded, leaning back in my chair, “When people say ‘nitrogen is nitrogen is nitrogen’, that’s not true at all then?”
“Well, it’s true for the plant,” he responded “But not for the soil, no.”
That might not be a big deal for everyone, but it is a big freaking deal for me.
I have never felt right about the nitrogen is nitrogen is nitrogen argument. When pressured, I summed it up by saying my issues with synthetic nitrogen was that it was a fossil fuel byproduct, but that’s never been my only concern. It just seemed to me that there was no possible way that synthetic nitrogen had the exact same impacts when you applied it as organic sources of nitrogen do. Synthetic nitrogen, I surmised, added nothing but nitrogen to the soil. In a world where people often add fertilizers that plants don’t need to their soil, which then end up in our water ways, one might argue it’s a good thing that we are able to isolate the exact nutrient our plants need and apply only it, but there are still some issues with that. Synthetic nitrogen doesn’t add organic material or beneficial bacteria or fungus or any of those other mysterious, as of yet undiscovered elements that turns out are totally crucial for healthy plants, things that are added to the soil in nature through things like manure and decomposing plant or animal tissue. It doesn’t put more carbon in the soil. But it does turn out to add one extra thing that organic fertilizers don’t, and that’s salts.
Salty soils are a serious problem in agriculture, as well as landscapes and gardens in the dry western states where we are likely facing down water crises in the next few years. Salts make it difficult for plants to uptake the water they need to survive, meaning the more salts in your soil, the more water you will have to add to keep your plants adequately watered. Excess soil salinity will also decrease the biodiversity of your soil, killing beneficial bacteria, fungi, and animals like worms and nematodes. You can leach salts out of your soil (by adding tons of water, as the owner of this lawn was instructed to do), but they never really go away. You either end up pushing them over to the next guy’s property, or you push them down lower than your roots go in the soil. The problem is, the salts don’t stay there unless you keep your soil constantly at the right moisture level. As water evaporates from the soil, it will pull the salts back up with it, so you have to constantly keep applying water, to keep the salts down and evaporation to a minimum.
Now imagine that if you are constantly adding more salts to the soil. Like all of our conventional agriculture does. In massive amounts. All the time. All over the world.
I think that organic nitrogen sources would likely contribute to soil salinity over time too, but synthetic nitrogen is a concentrated, isolated nitrogen that obviously does it at such a faster and higher rate that CSU felt it was only necessary to call out synthetic nitrogen for adding salts to the soil. Clearly, if one type of nitrogen makes your soil saline, and the other doesn’t, the argument that nitrogen is nitrogen is nitrogen is totally bunk. There is a significant difference in the types of nitrogen you apply to your garden, landscape, or farm. It would even stand to reason that the two different types of nitrogen would have a different impact on the eventual makeup of the plant, and say, the nutrition content of the edible portion of it. Healthy soil grows healthier and more nutrient dense plants. Dead, salty soils don’t grow the best plants.
When we were learning about soil salinity in my soil sciences class last spring, I actually spent a couple of weeks feeling very depressed. The scope of the problem was enormous. We needed to fertilize our crops, because plants need nitrogen to survive and they deplete the soil of nitrogen very quickly as they grow. But adding fertilizers to the soil made it saline, ruining it’s texture and requiring ever increasing amounts of water to keep the crops alive. But the more water added, the more salts were pulled up from deeper in the ground. It seemed like a vicious feedback loop that was hurling us all down a one way path to doom. Was there any solution? Any way to grow enough food to feed us all without destroying our soil and using up all my drinking water? My professor had no answer for me. I was terrified. I eventually made up my mind that the most we could do was try not to over fertilize. That maybe, if we added just the right amounts of nutrients to our soil, our soil would be able to handle it without being destroyed. Then we could grow less nitrogen intensive plants, and use farming methods that reduce the amount of nitrogen needed.
But now I wonder. I wonder if the problem is just synthetic nitrogen. We use massive amounts of synthetic nitrogen in conventional agriculture. That nitrogen not only may be worse for the soil than organic sources of nitrogen, but it’s also dangerous to produce (accidents and explosions are common) and it produces a ton of CO2. I may be changing direction on what I think is the least important choice for a climate friendly diet. To be fair, the best organic source of nitrogen comes from meat and dairy production, and that is not without it’s ethical, climate, and human safety qualms either, but I think it still comes back pretty clear for me. Our choices of nitrogen options makes a big difference, if not to how the plant utilizes it, then certainly to a lot of other issues that are at least equally important to me, and probably should be equally important to anyone else growing plants or eating food or breathing air.
Sometimes I think that we forget that we aren’t growing plants in a vacuum. We take a very reductionist approach to the whole growing plants thing, and think “If a plant needs nitrogen, then give it nitrogen. There, done.” But it’s not just the plant that we’re interacting with when we grow things. The things we do for our plants also impacts the soil, the air, the other organisms around our plants, the water in the creek a mile away from our plants, and dozens of other things that your plant depends on as much as it’s nitrogen supply. Reductionism has it’s place, of course, but we also need to take the time to see the big picture. The nitrogen source we choose for our yards, gardens, and farms in fact does make a very big difference to the plant. Nitrogen is not nitrogen is not nitrogen, not once you apply it to your garden, at least.
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