Dairy Channel: Time to change way you utilize manure


If concerns about the environment (runoff of manure nutrients from crop fields) and the possibility of overloading some of your fields with phosphorus and/or potassium have not caused you to carefully evaluate the way you handled livestock manure in the past, perhaps this will.

Importance of manure.

The current supply situation and price of nitrogen fertilizers will help you realize that the manure your stock produce is a valuable and useful resource.

With anhydrous ammonia nitrogen fertilizer prices projected to reach $400 per ton (carrying prices of other forms on N along with it) this spring, along with the possibility that you may not be able to get the amount of nitrogen fertilizer you have used in the past regardless of price, you undoubtedly realize that manure has become an even more precious commodity on your farm.

I hope this article will help you to find ways to better utilize manure as a crop nutrient source and, at the same time, make your farm more efficient, more environmentally secure and more profitable.

The first thing you should do is check with your fertilizer supplier now (if you haven’t already) and price your spring nitrogen and other fertilizer needs before further price increases occur.

Why is nitrogen so costly this year?

The major cost component of making nitrogen fertilizer is natural gas. The production of anhydrous ammonia is the first step in the production of nearly all nitrogen fertilizer products.

According to the Fertilizer Institute’s 1999 production cost survey, the production of one ton of ammonia requires an average of 33.5 million British Thermal Units (MMBtu, the standard measure of thermal energy in the U.S.) of natural gas.

Natural gas is problem. he reason for the fertilizer cost increase is the same reason that home heating bills have skyrocketed this winter. The demand for natural gas supplies has suddenly increased far beyond the ability of suppliers to keep pace.

Demand for electricity has increased about 4 percent per year in recent years. Of planned new power generating plants, 92 percent of the generating capacity now under construction will be fueled by natural gas because of environmental considerations and advances in efficiency of gas turbines.

The Energy Information Administration estimates that U.S. demand for natural gas will increase from 3.7 trillion cubic feet in 1998 to more than 9 trillion cubic feet in 2020. An additional factor has been severe cold weather this winter.

Natural gas spot prices have increased sharply from an average of $2.35 per MMBtu in January 2000 to an average of more than $8 for the month of December 2000.

Price is staying high.

It appears that the price of natural gas will remain high, at least for the near term. Much of domestic (U.S.) nitrogen production capacity is idle because prices are being kept below present cost of production by the availability of imported N products.

At $8 per MMBtu of gas the raw cost of gas to produce a ton of ammonia is $270. Adding costs of manufacturing, storing and shipping, the price of ammonia to a Midwestern farmer could reach $400 per ton, or 24 cents per pound of N.

This compares to an average price of $230 per ton or 14 cents per pound of N over the last 10 years. If the price of gas goes to $10 per MMBtu, the cost of gas to produce a ton of ammonia goes to $363.

Dealing with higher N prices

Even if you could get the nitrogen supply you want, economics dictate that you would apply less per acre this year because the optimum N rate per acre is lower at a higher N price.

The optimum N rate is that place on the yield response curve where the last pound of N applied is just paid for by the yield increase produced from that last unit of N.

Data from Illinois suggest a reduction in application rate of 6 to 7 pounds of N per acre for each 5-cent increase in the price of N per pound (5 cents per pound is about equivalent to an increase of $82 per ton of ammonia).

In both corn-after-corn and corn-after-beans situations, adjusting the N application rate downward to accommodate a 5-cent increase in the cost of a pound of N will only result in a yield decrease of about one bushel per acre.

Table 1. Effect of changing nitrogen price on rate of N needed to attain economic optimum yield and the effect on yield of changing the N rate.

Price      Price      Corn-Corn      Soy-Corn

$/ton      S/lb      Opt. N Yield@opt N      Opt N Yield@opt N

230       0.14      161      150      146      170

312      0.19       155      150      139      169

394      0.24      149      149      131      168

476      0.29      136      147      117      166

640      0.39      130      146      110      164

722      0.44      124      145      102      163

Note: These data should not be used to predict yields or optimum N application rates for your farm. The only way to determine optimum application rates for your farm is to conduct controlled experiments under your cropping conditions and apply your production costs and expected crop prices.

As N prices increase, optimum N application rates and resulting yields change, and profit per acre decreases.

Using data from Table 1, above, as N price moves from $230 per ton to $394 , optimum N rate drops from 146 to 131 for corn-after-beans, but cost of N per acre increases from $20.44 to $31.44.

At the same time, yield drops by 2 bushels per acre and net revenue per acre drops by $14.80 per acre.

Dealing with limited N supplies

Limited supplies and higher prices mean you can afford to take steps to better utilize the N in livestock manure. Allocate your limited purchased N and manure supplies over the entire acreage of corn you plan to grow.

Make sure your fields get credit for home-grown nitrogen. Reduce N application rate by at least 40 pounds per acre for corn following beans.

Reduce N application rate by at least 100 pounds per acre for corn following alfalfa. Make sure you trap and make use of manure nitrogen whenever possible.

Making the best use of manure nutrients

According to Ohio State University Extension’s Food, Agricultural and Biological Engineering AEX Fact Sheet 707-91, the following guidelines will help you to make best use of manure nutrients.

* Test manure to determine nutrient content and select an application rate that will meet crop nutrient needs without causing nutrient runoff or excessive soil nutrient buildup.

* Do not apply manure to saturated soils or frozen soils with more than a 6 percent slope.

* Calibrate manure application equipment to obtain the desired application rate.

* Incorporate manure to prevent excessive odors and to reduce nitrogen losses.

Table 2. Nitrogen Losses During Land Application of Manure

Percent of nitrogen applied that is lost within four days of application.

Application method      Manure type      % Nitr. lost

Surface Spreading      Solid      15-30

      Liquid      10-25

Surface Spreading With       Solid      1-5

Immediate Incorporation      Liquid      1-5

Injection      Liquid      0-2

Spray Irrigation      Liquid      15-35

Source: Midwest Plan Service. 1985. Livestock Waste Facilities Handbook. MWPS-18

You should also check Ohio State University Extension Bulletin 604 Ohio Livestock Manure and Wastewater Management Guide for information and recommended manure application rates for meeting crop needs and reducing the potential for pollution of surface and ground water.


These recommendations suggest that for soils below Bray P-1 Phosphorus levels of 60 pounds per acre (30 PPM), you can use manure application rates that will supply the N needs of the crop.

At Bray P-1 levels from 60 pounds to 250 pounds per acre, (30-125 PPM) surface manure application rates should be limited to N needs of the crop or P removal rates of the crop, whichever is less, but if manure is incorporated, you can apply enough to meet the N needs of the crop, regardless of P removal rate.

For Bray P-1 levels above 250 pounds per acre (125 PPM) surface applications of manure are not recommended.

However, manure can still be safely incorporated into soils up to Bray P-1 levels of 300 pounds per acre (150 PPM) at rates to meet the N or P needs of the crop, whichever is less.

See OSU Extension Fact Sheet AEX-710-95 for additional information.


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