Comparing Composted and Raw Manure in Crop Production

Final Report for FNC93-045

Project Type: Farmer/Rancher
Funds awarded in 1993: $1,600.00
Projected End Date: 12/31/1994
Matching Non-Federal Funds: $2,500.00
Region: North Central
State: Minnesota
Project Coordinator:
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Project Information


Greetings from Crazy Acres. I farm here with the help of my wife Nancy and our two daughters, Tiffany and Madelaine. I would like to take this opportunity to thank you for the assistance from you grant program that will help us share some of the things that I have learned from the composting experiment which I began about 5 years ago. The farming enterprise here is both very simple and complex. I started farming about 20 years ago when I bought the 160 acres that form the core of the business. These are some poor quality acres of very hilly, highly erodible land located on the Buffalo Ridge in southwestern Minnesota. From the very beginning, I have been thoroughly committed to a style of agriculture that strives for near zero pollution and emphasizes soil, energy and water conservation. The operation has grown slowly. Along with the 110 tillable and 35 acres of native prairie pasture at home, I now rent 230 acres. Of this, 30 acres of pasture connects with mine; 200 acres are about 5 miles away. These 200 acres is half tilled and half in native prairie pasture.

Our livestock consume nearly everything that I harvest form the soil. Both the dairy and feeder cattle enterprises are rather low capital in style with an emphasis on grazing and forage. We milk about 30 cows and generally have total herd of about 150 to 170 head of cattle. The 65 acres of pasture at home are rotationally grazed by dry cows and young dairy cattle, while the 100 acres of pasture ways from home are grazed by steers. My intentions are to implement a non-intensive rotational system there also. While I do fatten out a few steers, my cattle feeding could best be described as a back grounding operation. The grazing at home is also non-intensive; we utilize 6 paddocks and rotate on a weekly to bi-weekly pattern depending on the grass.

Besides being somewhat philosophically uncomfortable with the commonly practiced method of fattening cattle, one of the reasons I do not emphasize fattening cattle is the fact that I just do not raise that much corn. Usually my 200 acres of tilled crop production is split between 70 acres of alfalfa, 50 acres of small grain, 80 acres of corn and quite a few waterways, sloughs, and other forms of grass production. My crop production is nearly totally organic in practice. I attempt to rotate tillage as well as crops; we utilize ridge tillage when possible, but by far the majority is done with conventional minimum tillage. I use a lot of cover crops (this winter I have over 50 acres in rye cover) and plow downs.

As I stated, this operation is really very small and simple in design. Capital outlay has been kept to a minimum. There are not a lot of acres or a lot of cattle involved. The only herbicide I have used for over 10 years is a little thistle control in the pastures, the only insecticides have been some fly and lice control on my younger cattle. I now of some homes that use as much electricity for living as we do for living and operating. My total gas and diesel fuel purchases generally are between 10 and 15 gallons per acre of tilled land, and that has to stretch over the livestock enterprise with its manure disposal, fee grinding and silage handling as well as a certain amount of custom work that I do. The complexity comes in the picture when you try to make that all work together to form a whole unit of production that keeps spinning off quality food for people without polluting our environment and still provide a living for the people that live here on Crazy Acres.

The research and demonstration project that I started in 1990 was an attempt to evaluate composing a manure management method for the small to medium sized operation. I think that we should review the actual process of composting and discuss the application of compost so that everyone understands what we are dealing with. Otherwise, I will review actual performance data from the earlier years only in a cursory manner when it relates to an issue in this year’s report. Anyone who would like more detailed information on test plot performance in the earlier years is encouraged to contact me or ask the Energy and Sustainable Agriculture Program at the Minnesota Department of Ag.

One of the greatest barriers for most smaller operators is the initial cost of obtaining a compost turner. We formed a group of four farmers to split the four thousand dollar price of a used flail type turner. This made the acquisition more palatable, but it greatly complicates the matter of logistics and time. The greatest majority of our labor time is spent in transporting and setting up the turner; the actual turning time is really only a few minutes per windrow. If someone is interested in starting to compost, they should not let the lack of a turner stop them. Each one of the four cooperators has experienced surprising success with composting turning the windrow using a front end loader or a skid steer. The actual turning process takes longer, but there is no set up or cleaning time. Although the end product may not be quite the same because if doesn’t get blended as well or because the heat may not be as uniform, you can still get close. And this is one of those rare cases where there are no harmful effects caused by not achieving the best. I have heard of several different methods of composting using only machinery most farmers have. I have heard of several different possible sources of lower cost turners being developed. The point is if there is a benefit to be gained; perhaps the best route is to get started with what is available.

Composting works best with manure that contains a fair amount of bedding. Technically speaking, it should have a carbon to nitrogen (C:N) ration that falls within the range of 20-30:1, and it should have a moisture content of 40-60%. Practically speaking, if you are taking manure from a free-stall dairy barn, you are going to have to mix it with some pen-packed manure to get good results. I have never had trouble with it being too bedded or too dry, but I understand that in certain climates it can happen.

We put our manure in windrows using an ordinary box spreader. You will learn that the proper size for your windrows is determined by the equipment you have for turning them. Don’t start too big; I did. As I stated, we use a Wildcat flail type turner on the three-point hitch of a 100 hp tractor. Upon aerating and turning, microbial activity raises the temperature inside the windrow to a very warm 130-160 degrees F. the idea is to keep the temperature above 125F for as long as you can, and to get the outside edges mixed in so they are exposed to the heat and the microbial activity. A windrow can usually be turned into compost with 5 or 6 turnings. The end product will be dark in color, friable and have a slight musty, earthy smell to it.

Compost is not a difficult product to work with in terms of needing very heavy duty equipment to handle it. It does pose a problem in that it is difficult to apply at low enough rates to make efficient use of this rather concentrated fertilizer. The ideal application rate would probably be around 2 tons per acre. A normal box spreader at normal speeds will deliver 7-12 tons per acre, and the fine texture of the compost allows it to slide under the main beater with a resulting streak of excessive compost. Perhaps the nicest solution is the newer style slinger spreader that uses a slide on the front-side delivery. A box spreader with a lower beater or a pan under the apron will at least help with the uniformity, but it is still difficult to achieve a low rate.

The first 3 years of the project were oriented towards evaluating the performance of compost in the field. In 1990 the test plot had six strips that compared to raw manure in the production of oats. In 1991, I spit each of the strips into three strips that are four rows wide of 13.5 feet. Thus I have replications of comparing raw manure, compost and a control where nothing has been applied. These replications produced corn in 1991, oats in 1992, and alfalfa in 1993 and 1994. Fertilizers were applied in the spring of 1991 and the autumn of 1991. No fertilizers have been applied after that, thus the crops of 1993 and 1994 have been produced a ton residual fertility. I wanted to do that to test the theories that compost is relatively stable form of fertilizer that has long term beneficial affects on the soil characteristics such as tilth, microbial activity, organic matter content and permeability. These theories would imply that the benefits of compost may go beyond the actual fertilizer values as measured by N-P-K.

The specific purpose of the project his year was to evaluate the performance of compost versus raw manure in the third crop year after application. The last two applications of compost and raw manure that would have significance for this test plot were made in the spring of 1991 and in the late autumn of 1991. Table 1 shows the split and total tonnage of the two fertilizers applied and the pounds of N-P-K per application. The total tonnage of the raw manure was slightly more than double the tonnage of compost. I would have preferred to have had less raw manure. I think that for comparison purposes it is necessary to apply considerably more raw manure for a couple of reasons. First, there is about a 50% reduction in the volume and tonnage of the raw manure in the composting process. I think it is only right to compare using roughly equal amounts of raw material. Secondly, we actually are not that far from equal amounts of phosphorous. I knew that I was going to use alfalfa for the long-range test, and phosphorous is usually the first limiting factor in alfalfa production. No matter how you look at it, the test is actually loaded a little bit in favor of the raw manure.

[Editor’s note: There are some graphs and tables that could not be posted online. If you would like to see these please email us at or call us at 800-529-1342. Thanks]

In order to do this evaluation we will look at the yield figures in terms of quality and quantity. We will look at the alfalfa population and the weed population. Perhaps I should explain the method that I used to take this data. All measurements were taken using a 2 square foot wood frame which I threw down at random a two different location sin each of the 18 strips when the alfalfa was still standing just prior to swathing. For the first location I worked my way across the strips about 30 paces form the end of the test plot where I could accurately see the marking flags that I had placed in the fence line at the end of the plot. After I took the first measurement in each strip I turned and paced 30 steps down the strip and threw the frame down at some distance in front of me. I used this method to try to eliminate the bias that I might have. At each location I would count the alfalfa crowns, and then I would count and identify the weeds. The biggest problem here came in counting the quack grass. I attempted to count the clusters of quack grass that were capable of independent growth. After I did the weed counts at each location, I took a hedge trimmer and cut all the growth inside the frame. The samples from each strip were weighted, and then chopped, combined with all the samples from the respective treatment, sampled again and sent to DHIA for quality analysis.

The yield weights that we see here are indicative of what anyone could obviously see when observing the test plot. There was such an obvious difference in the strips. The control strips were obviously suffering form lack of fertility; the first cutting in those strips struggled to reach 10-12 inches while the compost treated strips were well over knee-high. While there was not as much difference in height between the compost and the raw manure strips on the fist cutting, it was noticeable that the raw manure strips had a lot more quack grass standing above the alfalfa. After the first cutting, the compost turned green again days earlier than the raw manure strips did, and then you could see that there was a much better stand of alfalfa on the compost strips. That was when the performance really started to vary. With the second and third cuttings there was a marked difference in the height and density between the compost and raw manure treated strips.

Overall, the yield of the compost treated strips was 6.9 tons dry matter/acre; nearly double that of the raw manure with 3.9 tons dry matter/acre. By way of comparison, the control strips had been depleted to where they produced only 2.3 tons dry matter/acre.

I didn’t do all that well on the quality tests for the first cutting this year either. I wanted to handle a huge crop on 30 acres of alfalfa 5 miles from home before I devoted the time necessary to take all the measurements for this test plot. By the time I had that all hauled home and put in my silo, I was running on the mature side to say the least. But perhaps it wasn’t so bad: I need a certain amount of alfalfa with adequate fiber to feed for back grounding steers but more importantly it called attention to something that becomes apparent when you take a closer look at the quality test. On both the first and second cuttings, the compost treated alfalfa comes back with the lowest RFV rating. Yet on all three cuttings, the compost treated samples had quite a bit higher protein content. I’m sure that the higher fiber content of the compost treated hay is due to the fact that the compost treated strips would blossom several days earlier than the other two. This results in a higher fiber content, which lowers the RFV. The compost treated samples also had lower energy levels. That could be due to earlier maturity, and it would explain the lower RFV. But why does the protein content remain higher? Is it due to the fact that there is a better alfalfa population? We can note that the raw manure test had the lowest first cutting protein content and the highest quack grass count. But I do think that we have to compare the contents of the four minerals calcium, phosphorous, magnesium, and potassium. The compost samples had the lowest calcium on the first and third cuttings; it virtually tied for lowest on the second. Compost had the highest potassium content on all three cuttings. Compost had the highest phosphorous content on all three cuttings. Compost had the lowest magnesium content on the first and third cuttings and tied for lowest on second cutting. Is the compost supplying a more balance diet to the alfalfa plant, which enables it to produce more protein? It would be interesting to harvest each treatment at the same maturity with the same energy and fiber levels and see where the protein and RFV values would come in.

With the second year of alfalfa production, the weeds I was counting were a lot different than the ones I counted when I was producing corn or oats. At that time I was counting annual grasses such as foxtail and annual broadleaves such as mustard and lambs quarter. This year’s weed counts are almost completely dominated by perennials. While the count of broadleaf weeds might actually show a few more weeds on the raw manure treated strips, they are so sporadic that I do not think that we should consider them to be a scientific value. The major grass infestation was quack grass. I am not sure that I counted quack grass correctly; I tried to consistently count each spot where there was a viable shoot emerging from a root structure. I realize that does not account for the wide variation in the size of the crowns, etc. When I averaged it all out, I found 13.3 rooted spots per square foot in the raw manure treatment, 8.4 in the compost and 5.6 in the control.

It is a little bit easier to know what to count with alfalfa. But here again there is a wide variation in the vigor and competitiveness between different crowns. This was especially true in the control strip; when I took the counts for the second cutting, some crowns were so weak that they were producing only one spindly stem that was only a few inches high. I counted all of them, and the raw manure treated strips had the lowest population at 6.06 crowns per square foot. The compost treated strips had the highest population with 9.5 crowns per square foot and the control was in the middle with 7.6. In other words, where I used the compost I had the population and the fertility to make good hay. With the control, I had the population but lacked the fertility. If the fertility was present on the raw manure treated strips, the population was not there it use it.

In 1991 the compost strips came in with the highest corn yield; there was a 7.2 bu/acre advantage over the raw manure and a 15.5 bu/acre over the control. With a $44.40 fertilizer cost for compost and a $40.50 fertilizer cost for raw manure, the compost had a $10.95 higher income than the raw. However, with no fertilizer cost for the control, the control had a $9.52 higher income than the compost. In 1992, poor weather gave us poor oats crop, and all three lost money. Even though the compost yielded highest, the control with the lowest yield lost the least money.

The yields of alfalfa on the test plot have been very high, but the quality of the first and largest cutting was poor. Let’s put a lower value on the hay at $75/ton of dry matter. It costs about $1 in cash expense for fuel and repairs to produce a ton of compost. Although that compost already produced a 7.2 bu corn increase (1991), a 9 bu oats increase (1992) and a 4.2 ton alfalfa increase in 1993 over the raw manure, we will put that expense of $13 on the costs for 1994. I figure it costs about $40 to spread raw manure on an acre, so that would give us a $53 fertilizer cost to treat an acre with compost, not figuring the capital cost of the turner. With a 3 ton increase over the raw, the compost would gross $225.00 over the raw. Subtract the $13 extra cash expense and we have a net increase of $212.00. With a 4.6 ton increase over the control, the compost would gross $345.00 over the control. Subtract a fertilizer cost of $53 and we have a $292.00 net increase over the control. Of course we must remember that we need to take the capital investment for the turner out of that; however, we also have all previous year’s yield increases to help with that. Composted or not, this test plot has surly show the long term effects of a good manure management program.

I should have taken soil test after the third cutting. I was disappointed with the soil tests I took earlier in the project, but with yield and quality analysis differences like this, soil tests may have shed some light on the project.

I have built a “bad” reputation around here for being a strong supporter of sustainable Ag. So I have talked to a lot of people locally about this. I have the plot well marked on a major county highway. I have very poor attendance at field days here. I have just compiled all the results; I hope to share them with some local papers. But what I would like to do is publish some type of major article or paper about the entire project. Also, if you would ever like me to present my findings at a meeting or workshop, I would try to break away to do that.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.