Nitrogen Management Guidelines in New NRCS 590 Standard
By Ted Funk
email funkt7@gmail.com
ph. 217-369-7716
Last year, Illinois undertook a major overhaul of the National Resources Conservation Service
(NRCS) Nutrient Management Conservation Practice Standard Code 590. If you are familiar
with the "nitrogen risk assessment" that we used for Illinois crop fields prior to 2013, you will
see some changes in the new 590 Nutrient Management Standard. Those changes and how they
may affect Illinois swine producers are the subjects of this article.
One of the main reasons swine producers should be concerned with the new 590 is that the code
is built into the Illinois NRCS Comprehensive Nutrient Management Plan (CNMP). A current,
valid CNMP for your operation is your "passport" for participating in many facets of the
Environmental Quality Incentive program (EQIP), and it also provides a solid basis for
compliance with state (LMFA) and federal environmental regulations (NPDES CAFO). But the
590 standard is not particularly easy reading, as it references other documents and worksheets.
I wrote about phosphorus and the new P-index a few months ago. Nitrogen (N) management in
the eastern U.S. is more in the news than phosphorus now, mainly because N management
affects so many row crop producers. Keeping nitrogen in the crop's root zone is tricky.
Livestock producers applying manure to cropland have a couple of strikes against them: manure
application is expensive per unit of N applied, and the window of opportunity for applying
manure depends on weather, storage capacity, stage of crop, equipment and labor availability.
On the positive side, manure-based N goes on cropland in a form that is partly a slow-release
product (the "organic" nitrogen fraction).
First consider the soils and field characteristics that are affected. Some places in the state, where
nitrate leaching is not a factor, need to be concerned about phosphorus but not so much with
nitrogen. So here comes the 590 standard, the Nitrogen Management Guidelines part.
There is a list of Illinois soils giving the basic nitrate-risk factors. The list is by county and soil
series number. You can access the list through the Illinois NRCS field office technical guide
(efotg) at http://efotg.sc.egov.usda.gov/. Section IV of efotg has the state conservation practices
and specifications. Also open the Conservation Practices folder and under it, open the Nutrient
Management folder, because that folder contains all the documents related to the 590 Standard.
For nitrate leaching risk information, there is the soils list in an Excel spreadsheet and a nicelooking pdf map of the state. If none of your fields is affected by the nitrogen loss potential
factors—either soil type or tile drainage—you can focus your attention on phosphorus (that is,
after you skim through what the other folks need to do about nitrogen management).
But let’s assume you don’t know yet about your soils. Start with the soils maps for your fields.
If a soil is listed on the spreadsheet, and/or the field is more than 50 percent tile drained, you
need to look at the Nitrate Loss Potentials grid table for corn and then at the table for "Late
Spring Planted Summer Annuals." Both tables are in the Illinois NRCS Nitrogen Management
Guidelines document, also at the efotg folder. From the tables, you can quickly surmise the
practices that move your soils from high nitrate loss potential to medium or low. Any of the
options--split applications, use of cover crops, application timing, use of a nitrification inhibitor
and different crop rotations--can spell major changes in your manure management. You will
notice an emphasis on keeping a crop growing on the soil for more months in the year.
Your nutrient management plan is only as up-to-date as the standards it reflects. In Illinois, the
NRCS 590 Nutrient Management standard (February 2013) has some changes that you must
address for your fields. Nitrogen management guidelines are spelled out in new ways that could
change the system of manure handling on your operation. For more information, contact your
local NRCS office, or email this author at funkt7@gmail.com.
Illinois has a nitrogen management campaign -- the "Four Rs" -- right kind, right time, right
place, right amount. A manure-based fertility program can address the Four Rs. To read more
about Ted Funk's Four R analysis, visit the IPPA website at www.ilpork.com.
ERIN/TIM -- GOOD PLACE TO BREAK AND USE THE INFO BELOW ON THE WEB?
Right kind. Manure is the "right kind" of nitrogen fertilizer for many reasons. As I’ve said in
columns before, manure has some advantages over commercial fertilizer, one of which is the
various forms of N in the manure product. It contains two basic types of nitrogen that become
plant-available over time: one is the ammonium nitrogen, which is made available quickly
through the nitrification process in the soil; and the other is the organic nitrogen, more
chemically complex material broken down over time by soil processes into plant-available form.
If you are concerned about nitrogen escaping the system and leaching out of the root zone in the
form of nitrate, as either ammonia via volatilization into the air, or as diatomic nitrogen gas
through nitrification and then denitrification in waterlogged soils, the organic fraction tends to
hang around where it's put, weathering the various stresses on the system. That’s a good thing.
The 590 standard does require the user to pay for manure sample analysis that splits out the
answer into the two forms of nitrogen: ammonium-N and organic-N. Soils labs will give you the
total Kjeldahl nitrogen (TKN) and ammonium nitrogen (NH4-N) on the lab sheet. The organic
fraction is not directly analyzed. It is the difference in the two numbers. Knowing both numbers
helps you decide manure application rates. The 590 standard accepts a multi-year running
average manure nutrient content for calculating rates.
In Certified Livestock Manager Training classes over the years, you no doubt have seen the
application rate calculation done and realize that the organic fraction has an estimated decay
series of 50 percent per year. We have to acknowledge "estimated" decay series because the soil
processes are variable and complex. We only keep track of three years of organic nitrogen
breakdown after a manure application. After that, further organic N availability becomes
"background noise," and is too small to figure into the rate.
Right time. Here's the rub for livestock producers. Applying manure on row crop land means
you have to hit the window of opportunity in fall and/or spring. We've all been taught applying
nitrogen close to when the crop needs it is preferred. Probably one of the better uses of EQIP
funding is to improve and enlarge manure storage capacity, so you can have more control over
when manure is applied. There are so many things to avoid, in addition to the risk of
overtopping a storage: soil compaction, by having heavy equipment and injection tools on soils
that are too wet; disrupting spring planting; covering too much crop residue in the fall with the
injection equipment; heavy axle loads on rural roads; and more. A big manure storage, pumped
by big equipment to spread quickly when the time is right—what’s not to like about that?
But in the 590 standard, with timing also comes the admonition about observing soil
temperatures in the fall. Warm soil (warmer than about 50 F) means rapid nitrification of
ammonium-N, suggesting the nitrogen form is now in the soil solution as nitrate, and it is mobile
downward. The ammonium form of nitrogen is positively charged and tends to stay with the
soil, while nitrate is just the opposite, taking advantage of wet soil to move down away from the
crop root zone. That spells pollution potential. How do you slow down nitrification? Either you
wait for cold soil before you apply, or you put something in the product that inhibits the
biological process. Both choices are addressed in the 590 standard.
You have three nitrate loss potential classifications under the Illinois NRCS Nitrogen
Management Guidelines -- low, medium and high. Those classifications affect when and how
you can apply nitrogen materials to certain soils, and thereby comply with the 590 standard. The
number one transport pathway of nitrate into surface water is by tile drainage. For groundwater,
the most important prediction factor for nitrate contamination is depth to aquifer materials. It
follows that, to meet the standard, you must know your soil types and their tendency toward
shallow aquifer materials, and whether the fields are tile drained. You’ll note on the spreadsheet
list of high-risk soils the various factors as column headings: typical slope, drainage class,
particle size, estimated available water holding capacity and flooding frequency.
Right place. We already know about setbacks from surface water and wellheads, since we have
studied those in the CLM training classes and memorized the numbers. On pages four and five
of the 590 standard, underline a couple of extra setbacks from drainage ditches and tile inlets,
and you've got it. The choice to inject or surface apply manure may affect some producers. For
most situations, injection of liquid manure by way of a conservation tillage knife, sweep or
coulter system still provides the best combination of nutrient placement and retention.
Shallow soils over fractured bedrock, sand or gravel may require you back off on application
rates. That can be a problem with liquid manure injection systems that are already struggling to
reduce rates below about 5,000 gallons per acre. Can you make the injector wider or drive
faster? So before you purchase your next piece of equipment, assess whether you have fields
where only low rates of manure can be spread per single application.
Right amount. The starting point for plant-available nitrogen application rates is to put on no
more N than the crop will use in the growing season. For corn, the rate is supposed to be based
on the Maximum Return to Nitrogen (MRTN) calculation that reflects the price ratio of corn to
commercial N. Naturally, that leaves the manure application business hanging somewhat. But
as I have discussed before, unless the price of corn drops out of sight, the equivalent price of N
in manure lets us apply pretty close to the rates to which we are accustomed.
Speaking of customary rates, the 590 standard says that manure may be applied on legumes at
rates equal to the estimated uptake by the biomass. The Illinois Agronomy Handbook estimates
soybeans will take up about three pounds of nitrogen per bushel of yield. This means that if you
really want to put manure on soybean ground, you can apply at about the same N-limited rate as
you would for corn. That makes rate calculation easier for a rotation that includes soybeans.
Where you use irrigation to apply the total rate of liquid manure at one time, pay attention to soil
infiltration rate and water holding capacity. The irrigation amount should be based on crop
rooting depth. The point made by this part of the new 590 standard is this -- plan and limit the
liquid application so that the nitrogen stays in the crop root zone.