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posted by martyb on Wednesday October 31 2018, @07:21PM   Printer-friendly
from the Crap! dept.

Phys.org:

In a newly published study, researchers dug into how fertilizing with manure affects soil quality, compared with inorganic fertilizer.

Ekrem Ozlu of the University of Wisconsin-Madison and his team studied two fields in South Dakota. From 2003 to 2015, the research team applied either manure or inorganic fertilizer to field plots growing corn and soybeans. They used low, medium, and high manure levels, and medium and high inorganic fertilizer levels. They also had a control treatment of no soil additives to provide a comparison.

In the summer of 2015, they collected soil samples at a variety of depths using a push probe auger. Then they analyzed the samples.

  • Manure helped keep soil pH—a measure of acidity or alkalinity—in a healthy range for crops. Inorganic fertilizer made the soil more acidic.
  • Manure increased soil organic carbon for all the measured soil depths compared to inorganic fertilizer and control treatments. More carbon means better soil structure.
  • Manure significantly increased total nitrogen compared to fertilizer treatments. Nitrogen is key to plant growth.
  • Manure increased water-stable aggregates. These are groups of soil particles that stick to each other. Increased water-stable aggregates help soil resist water erosion. Inorganic fertilizer application decreased these aggregates.

Is it time to re-purpose the world's sewage into fertilizer?


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  • (Score: 1, Interesting) by Anonymous Coward on Wednesday October 31 2018, @10:41PM (2 children)

    by Anonymous Coward on Wednesday October 31 2018, @10:41PM (#756227)

    Manure significantly increased total nitrogen compared to fertilizer treatments. Nitrogen is key to plant growth.

    OK, so if organic fertilizers are as amazing as this summary makes them sound then something doesn't really add up. The discovery of the Haber process in the early 20th century truly revolutionized agriculture. It is not a big stretch to say that it is perhaps the single most important scientific discovery ever made. The Nobel prizes awarded for its discovery are well deserved.

    The industrial production of ammonia is a big part of what made it possible to achieve the ~quadruple amount of agriculture output for the same amount of farmland, compared with 19th century techniques, and is a big reason why we can sustain ~8 billion people on this planet today. Today, about half a billion tonnes of fertilizer is produced via the Haber process every year. It's estimated that around half of all the nitrogen atoms in your body are outputs from the Haber process.

    So what I'm not understanding here is: how did the Haber process achieve such astounding results if the organic stuff used prior is so much superior?

    TFA doesn't have the answer. I don't know either. Perhaps it's something simple... like maybe it's just impossible to produce the required amount of manure compared to the scalability of industrial processes.

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  • (Score: 3, Informative) by Hartree on Thursday November 01 2018, @12:23AM

    by Hartree (195) on Thursday November 01 2018, @12:23AM (#756255)

    They're not mutually exclusive. There are several effects going on. Yes, before chemical fertilizers they did use manure and plowed the stalks and debris back in. But, you only have so much of that. i.e. N cattle only give you N cattle's worth of manure and X acres of grass/corn can only feed so many cattle.
    The Haber process and being able to mine phosphate and potassium containing rock allowed people to put on much more nutrients. This vastly increased yields. So did hybrid plants.
    Now, the organic material from manures tends to hold the nutrients in the soil and less of it leaches out due to rain. The chemical fertilizer itself doesn't directly provide that benefit. However, it does at least some of it indirectly. Since you are producing so much more vegetable material (stalks, roots, leaves) that get plowed back in, that material does help hold the nutrients. If you have that, and also put on manures, then you have the best of all. That's why they spread the sludge from sewage treatment plants on fields. Not only does it help much like manuring the field (because it basically is doing that) it's been treated and allowed to digest down so you don't have the problem of putting on so many direct human pathogens that are still viable on your field (tetanus, anyone?)

    The thing you have to watch is what else is in the sludge. You can get metals getting concentrated in it from the treatment process if they aren't careful. So, you monitor for that.

    Where I live, you see people out on 4 wheelers with GPS antennas on them taking soil samples. They're mostly checking for nutrient level and soil chemistry (pH especially) but also to see if they are getting accumulations of metals, or salts, etc.

    For controlling pH, they spread a lot of slaked lime on the fields. That's also recycling. The lime comes from water treatment plants and is a waste product there. They spread it on the fields and it helps keep the pH in the right range. (Unless you're growing something that lives acid. Blueberries for example. They love acid, say pH 4.5 - 5.5) But rain is usually a little acid, so that's not usually the problem around where I live. (And they don't grow many blueberries here. :) ).

  • (Score: 3, Interesting) by Phoenix666 on Thursday November 01 2018, @12:57PM

    by Phoenix666 (552) on Thursday November 01 2018, @12:57PM (#756438) Journal

    I've posted this many times before, but terra preta [wikipedia.org] that the Amazonian Indians created is much more fertile than the artificial fertilizers. Since it was discovered to be man-made, scientists have been trying to re-create it. Human and animal excrement are components in it.

    I have read before that soil scientists who studied the stuff created by pre-Columbian people in the Amazon basin calculated they could get an 880% boost in crop yields [naturalbuildingblog.com]. Can you imagine getting 880% more out of the patch of land you're farming?

    --
    Washington DC delenda est.