Manure Nitrogen Mineralization Research Update

Charles Wortmann Author

01/22/2019 Added

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Research Update for Land Application Training 2019

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[00:00:05.707]My name is Charles Wortmann.
[00:00:07.204]I'm a professor of agronomy and extension soil specialist
[00:00:10.671]at the University of Nebraska.
[00:00:12.807]And today's topic is
[00:00:14.579]Improved Use of Applied Organic Nitrogen.
[00:00:18.226]We feed a lot of beef in this state,
[00:00:20.637]and that results in the excretion of a lot of nitrogen.
[00:00:23.604]Some of it goes off into the air,
[00:00:25.935]but a big part of it is applied to agricultural crop land.
[00:00:31.674]That organic nitrogen,
[00:00:33.534]together with that from other animal manures
[00:00:36.072]and municipal bio-solids and other sources,
[00:00:41.104]may equal the equivalent of 150 pounds of nitrogen applied
[00:00:45.389]to 1.5 million acres pre year.
[00:00:49.909]So it's a lot of nitrogen.
[00:00:52.040]And unfortunately, the availability of that organic nitrogen
[00:00:55.780]is poorly predicted due to differences
[00:00:58.150]in the organic material properties,
[00:01:00.580]as well as climate, soil, management,
[00:01:03.330]and their various interactions.
[00:01:05.550]We do have estimates
[00:01:06.870]on fertilizer nitrogen substitution of organic N
[00:01:10.780]expressed as percent of the organic N applied,
[00:01:14.720]and these are 25% for cattle manure,
[00:01:17.700]35% for swine and some poultry manures,
[00:01:20.970]45% for other poultry manure,
[00:01:23.900]15% for compost, and 35% for municipal bio-solids.
[00:01:29.500]These estimates are conservative,
[00:01:32.040]intended to protect against under-application of nitrogen.
[00:01:37.660]However, producer confidence tends
[00:01:39.630]to be low in these estimates,
[00:01:41.260]and the over-application of fertilizer N
[00:01:44.400]to manured fields is common.
[00:01:47.900]So we have been conducting two continuous corn studies,
[00:01:52.420]one with feedlot manure loan,
[00:01:54.240]and this was at two locations for three years.
[00:01:56.600]Each trial had 120 plots.
[00:01:59.470]And the second was with eight organic materials
[00:02:01.950]at six sites for two years, each with 88 plots.
[00:02:07.180]And the topics addressed are adaptation
[00:02:11.260]of the corn canopy reflectance practices
[00:02:14.890]for guiding in-season nitrogen application,
[00:02:18.880]sidedress application for manured fields.
[00:02:23.300]A question is are the current sensor practices accurate
[00:02:27.200]for manured fields?
[00:02:28.900]And will different adaptations be needed
[00:02:31.700]for the residual effects of manure
[00:02:34.850]and different manure types?
[00:02:36.920]And the second topic is can we improve
[00:02:40.980]the prediction of fertilizer N substitution
[00:02:44.840]for different organic materials?
[00:02:50.060]I'm omitting a great deal of information here
[00:02:53.510]for the sake of brevity.
[00:02:55.270]But what we see in this slide, there are two figures,
[00:02:58.950]one from 2015 and another from 2016,
[00:03:03.460]the first from the year when the manure was applied
[00:03:06.490]and the second for the residual effect of the manure.
[00:03:11.120]And on the
[00:03:15.890]y-axis, we have N difference.
[00:03:20.030]Now, that N difference is the total fertilizer N needed
[00:03:24.410]minus that which was applied.
[00:03:27.040]Therefore, when we have negative values, such as here,
[00:03:33.000]it means that it's over-applied nitrogen.
[00:03:36.700]Positive values are under-application,
[00:03:40.350]and we want to be as near to zero as possible.
[00:03:43.580]I should point out that on the x-axis here,
[00:03:46.750]we have two lines of numbers.
[00:03:49.490]The upper one is the amount of nitrogen
[00:03:52.800]that was applied pre-plant
[00:03:55.480]with rates ranging from zero to 133 pounds per acre.
[00:04:00.060]And the second row is for the rate of manure applied
[00:04:03.650]with zero, 15, and 30 tons of feedlot manure applied.
[00:04:10.070]What we see here is with,
[00:04:13.580]here it's the 66 or 60 kilo
[00:04:16.710]and 90 kilo rates applied.
[00:04:19.130]If you look across on both figures,
[00:04:21.900]that's where we tend to be nearest zero.
[00:04:25.550]It's telling us if we apply, say,
[00:04:27.440]66 pounds of nitrogen pre-plant,
[00:04:30.360]that's when the technology will work best for us.
[00:04:33.860]But if we apply zero nitrogen
[00:04:37.070]or 33 pounds or 132 pounds,
[00:04:40.160]we tend to over-apply nitrogen with in-season application.
[00:04:47.530]And again, yes, the circles are added
[00:04:50.810]just to emphasize that point.
[00:04:53.100]Now, here we have results from the other set of trials,
[00:04:56.360]the six locations with eight materials.
[00:05:00.270]Those that you see circled
[00:05:01.730]in red are different livestock manures.
[00:05:04.520]Those circled in green are municipal bio-solids,
[00:05:07.490]different products.
[00:05:09.120]On the right, we have one circled in red.
[00:05:12.630]That's composted dairy manure.
[00:05:15.300]And in the middle, there is a Novazyme product.
[00:05:19.030]Novazyme has a plant in Blair,
[00:05:21.870]and it's the byproduct from that.
[00:05:25.230]What we're seeing here in the year of application
[00:05:28.010]that we've over-applied nitrogen
[00:05:31.120]with the in-season rate,
[00:05:34.530]that somehow the procedure did not work very well.
[00:05:39.700]Although in the following year, we were very close,
[00:05:43.290]on average just 16 pounds
[00:05:47.400]per acre under-applied.
[00:05:49.670]I think I said over-applied for the first season.
[00:05:51.990]Actually, it was under-applied by 47 pounds.
[00:05:55.890]So we do need to go back to the data
[00:05:57.890]and look more closely at this.
[00:06:00.570]Thank you, and have a good day.

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Manure Nitrogen Mineralization Research Update

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