Posts Tagged ‘nitrogen’

The Science of Nature: the history of tillage, fertilizer, and soil tests

Tuesday, April 26th, 2011

I have been doing further research on fertility and tillage, or working the soil.  My soil consultant is an advocate of mineral balancing for all minerals rather than just nitrogen, phosphorus, and potassium.  Those three are the elements that get the primary focus in conventional farming.  A guy named William Albrecht did a lot of research back in the 1920’s and ’30’s on the subject before commercial fertilizers were common. Today, Neal Kinsey and Charles Walters are the most well-known authorities on the subject.  At that time the primary fertilizer was manure because most farms were small and diversified.  Most farmers didn’t didn’t do much soil testing to know what they were doing. Results were based on observation, but that is vulnerable to misunderstanding.

periodic tableAfter World War II chemical fertilizers became available and were cheap and easy to apply, so farmers and the fertilizer salesmen took to manipulating mostly those three: N, P, and K. Cheap and easily-handled fertilizer led to larger farms and concentration on commodity crops like corn and soybeans. Nitrogen particularly has been cheap because it is produced using petroleum but it’s getting more and more expensive as petroleum stocks decline.  The other downside of focusing on just those three is that the overall fertility and health of the soil has declined steadily.  Advocates of mineral balancing point out that minerals and trace elements interact in the soil and affect a plant’s ability to take up available nutrients.  Just having lots of applied nitrogen in the soil does not mean the plants can use it.  Excess nitrogen often leaches away, ending up in our waterways.  The same is true of phosphorus which promotes algae growth in rivers and streams and then leads to lack of dissolved oxygen.  The means by which minerals become changed in the soil is the relative amount so materials with electrically positive charges versus those with negative charges.  Sounds like voodoo, but it is basic soils science.

pile of soilSoil tests on my field this year showed that I had 2.8 % organic matter (not too bad); pH of 6.6 (which is a little acidic for grain); nitrogen of 76 ppm (not terrible); sulfates of 15; phosphate of 43; calcium (Ca} of 44.32; and magnesium (Mg) of 41.97.  The problem is that all the nitrogen isn’t available and that other elements are in reverse balance or in oversupply.  I need the sulfates to be 50, the phosphates 250, calcium 68, and magnesium 12.  That 68/12 relationship of the last two is the linchpin of Albrecht’s theory of mineral balancing.  Sometimes it’s stated as 65/15 but it means the same thing.  Calcium and Mg not only affect fertility but the texture of the soil, it’s ability to hold moisture, and what weeds will grow fastest.  I won’t bore you with all the calculations, but the prescription was four tons of compost to neutralize some of the Mg and Ca allow more uptake of nitrogen, two tons of lime to help balance the Ca, and one ton gypsum for the same reason. Organic matter is also important because it bonds with the positively-charged elements that I need for plant growth.  My soils are heavy clay so they have a pretty good ability to absorb nutrients in the right balance, they hold water a little too well, and they are gooey. The compost plus my heavy, leguminous cover crop add organic matter which decays to humus which has a negative charge and so bonds with those essential minerals with positive charges.  I have a problem with wild radish and field bindweed, both of which like low calcium soils, so those will be suppressed with mineral balancing, I hope.

mushrooms poking their heads out in the fieldI’m on a program now to grow a cover crop each fall on the field to be planted the next year to grain and then apply the compost, lime, and gypsum as soil testes indicate.  It’s a big first-year expense but should decline rapidly after that.  What has confounded me, though, is testimony from many sources, included Kinsey, that what mineral balancing does really is foster microbiological growth in the soil like nematodes, fungus, and bacteria.  These guys do the real work of converting sunlight to healthy plants.  Every time you chop up the soil with a disc, plow, or cultivator you disturb that biological life.  On the other hand, most grain crops are opportunists looking for some soil disturbance to get established.  Archaeological research indicates that the first farming took place in southern Turkey where nomadic people took to spreading seeds of wild grains on riverside soils after flooding in spring.  How do I balance those two needs?

Periodic table image courtesy of BlueRidgeKitties.
Soil photo courtesy of Scout Seventeen.

Sustainable (and affordable) Fertilization on an Organic Farm

Monday, November 29th, 2010

One of the puzzles I have been pondering the last three years of my grain operation is how to affordably and sustainably fertilize and manage an organic crop.

Non-organic seed and fertilizer are cheaper, you can use chemicals to control weeds and pests, and the record-keeping is simpler. I am convinced, though, that petroleum based fertilizers are unsustainable for society and that endless use of chemicals is destroying the soil and the environment.

My first year of farming grain I didn’t have time to do anything but buy fertilizer so I bought the amount the rep suggested. I got a pretty good crop but the cost was astronomical and certainly not feasible for the selling price of the finished grain. I tried to grow a berseem clover cover crop but it failed miserably because there wasn’t any rain for quite some time after I seeded and then it was cold so the clover didn’t grow.

a mustard cover cropLegume cover crops create nitrogen, contribute biomass, suppress weeds, hold moisture in the soil, and help balance other minerals and trace elements in the soil. My second year I was leery of spending money on a cover crop that might fail but it was clear that I just couldn’t spend so much on fertilizer. I set a limit of $1000 for my 8 acres, and that turned out to be not enough. The result was a mediocre yield and really low protein levels in the wheat. I just didn’t have enough nitrogen and had too much of other things like manganese. Nitrogen has a major effect on protein and protein is necessary for good rising in bread. Last fall I put in a cover crop on the fallow (unused for a cash crop) ground and got a stupendous crop because of rain through the spring. I plowed that down in the spring and am planting into that this fall so I have the benefit of the nitrogen it created for my grain crop.

This fall I got that same soil tested and found that pretty much everything except manganese was still very low. Excessive manganese inhibits plant uptake of calcium and therefore limits the grain plant’s ability to use nitrogen available. To solve this I need to put in as much as 4 tons of compost per acre (as it offsets manganese) plus lime and gypsum on top of the cover crop. I can’t really afford to do all that in one year and have a reasonable sale price on the grain, so this fertility building is a 3- to 4-year project.

reed on the tractor getting ready to plantAnother aspect of the whole puzzle is the cost of tillage (turning the soil with farm implements and tractor) in labor and fuel, compaction of the soil from that tillage, calcium depletion from tillage, and suppressing weed growth. The simple way to suppress weeds is timely is using a disc or field cultivator but it’s not good for the soil because it destroys microorganisms and depletes calcium, compacts the soil making it less water absorbing and harder for plants to extend their roots, and it costs money. There has been a lot of interest and experimentation with planting into cover crops that have been rolled with a heavy implement mounted on a tractor. This avoids the excess tillage, suppresses weeds with the mulch of cover crop, and gets fertility from the legumes.

It seems to work well in the east where the Rodale Institute has been experimenting with it for some years. One of my problems is that I need to get a lot of organic matter from decayed plants into the soil to allow the microorganisms to grow and increase the carbon-to-nitrogen ration for plant growth, so I can’t skip the tillage right now. If I get the soil built up, theoretically I could grow a perennial legume cover crop that I could plant into with a planter that can penetrate the cover (no-till drill).

Another problem we seem to have in dryer climates is that the mulch makes great rodent habitat. I know of growers who have tried it and had major problems with them eating the cash crop. In Australia farmers often use what’s called a ley system where they plant a perennial legume cover crop that reseeds itself. Every other year or two they till in the cover crop and plant grains. In the intervening years they graze animals on the cover crop that has come back up. In California the problem is that those type of cover crops succeed as perennials because they are good at taking up water – water the grain plants need too. I’d like to try that but I’m wary of putting much land into an experiment without some more research.

green wheat plants with heads just filling outIn the long run, agriculture must manage with less petroleum input. With vegetables that’s more feasible than with grain, where much of the work is mechanized. I keep looking for the magic formula that would avoid the damage and cost of tillage while still building the soil, suppressing weeds, and keeping my costs as low as possible. In addition to the direct benefits of such a program, cover cropped fields are very effective carbon sinks, something we need desperately as we deal with climate change. At the moment I don’t have the answer and I can only experiment so much without risking a major mistake. I gotta have something to sell.

As of this date I have found I can get the compost mix I need but can’t get a spreader to put it on. I’m scrambling to find blood meal fertilizer (high nitrogen) and half the lime and gypsum really needed so I can get it on and plant before more rain. Using half the lime and gypsum is just so I can keep my cost of production down. If it increases yield from 1200 to 1800 lbs. per acre the fertilizer alone will still cost $.20 per pound, not to mention fuel and labor to put it on and the same for planting the grain. Besides that I’ve got the labor, fuel, and seed that went into planting the cover crop. All this has to be figured into my selling price and that’s why small scale organic grain is expensive. If I were using the same machinery on 30 acres and buying three times as much lime, gypsum, and compost or fertilizer the cost of the inputs would be lower and the machinery cost spread over more pounds of grain.

It looks like I may not get a cover crop in this year because of the rain, so next fall I will have to compensate with more blood meal and plant a cover crop on the field for the 2012 grain. Both the 2011 and 2012 crops will get lime and gypsum as the soil tests indicate with hopes that by 2013 I will have to spend far less money on them and my grain production will have increased substantially.

As with every farm, mine is an exciting gamble and experiment. I don’t claim to have any answers but I hope this post has informed and inspired you. I’d love to hear from other farmers about how they’re tackling these challenges.

-Reed Hamilton