Towards a sustainable milk production – Practical advice for reducing on-farm ammonia losses

Farming causes around nine tenths of ammonia emissions to the atmosphere. This article presents practical advice on how to reduce the on-farm losses of ammonia. These methods were demonstrated during the LIFE Ammonia project at the Swedish University of Agricultural Sciences Four main areas for reduction of ammonia emission were identified: - Adjust the protein level in the feed and improve the nitrogen efficiency. - Use best known techniques for stalling, ventilation and manure handling. - Change to slurry handling system with storage in a covered tank. - Use best known technique for spreading slurry.

Housing

Measure: Reducing air leakage in the manure handling system

Why are ammonia losses reduced?

There are very high concentrations of ammonia in the manure gutters and in the urine drainage system. If air is leaking into the barn via cross channels or urine drains the ammonia evaporation will increase.

Where is this measure suitable?

In all barns.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of the direct losses of ammonia in the barn. This is an important measure for good barn environment. Uncontrolled air leakage via the manure channels is unfortunately very common.

How much are ammonia losses reduced?

It is difficult to predict as the reduction depends on how big the air leakage was from the beginning.

What can be done?

Efficient barriers in the gutters or cross channels are very important. If these cannot be closed or sealed the outdoor air will enter the barn through these openings and cause ammonia evaporation into the building. This kind of leakage can be eliminated by sealed doors, water traps (slurry systems) or by an exhaust fan, taking air from the cross channels. Urine drains must be carefully sealed.

What are the costs for this measure?

A trap in a slurry channel costs about SEK 2500 (euro 270, USD370 ) and an exhaust fan costs about SEK 6000 - 10000 (euro 650-1000, USD 900-1500) depending on type and size.

Measure: Avoiding unnecessarily high temperatures in the barn

Why are ammonia losses reduced?

Ammonia evaporation is strongly related to the temperature and is reduced by lower temperature in the air and in the manure.

Where is this measure suitable?

Cows need for temperature is moderate and lowering the temperature in a cow barn is a simple and efficient method for reducing ammonia losses.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of the direct losses to the air.

How much are ammonia losses reduced?

In a study recently carried out in Sweden, the ammonia evaporation was reduced by 40 % when the temperature in the manure was lowered from 15ºC to 10ºC.

What can be done?

Avoid higher temperature than necessary for efficient production and good comfort. During the winter season the amount of ventilated air can normally be increased without any negative effects on cows.

What are the costs for this measure?

This measure does not result in any additional investment. In fan ventilated barns some additional operation cost for electricity might occur.

Measure: Reducing surfaces covered by manure

Why are ammonia losses reduced?

Ammonia evaporation is related to the size of exposed dirty surface, the bigger the area the more evaporation. The main part of ammonia evaporation originates from urine.

Where is this measure suitable?

To be considered when planning the layout of a barn.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of direct losses to the air.

How much are ammonia losses reduced?

The reduction is directly related to the size of exposed area. Calculations made indicate that by reducing manure covered areas by 20 % in cubicle barns the ammonia evaporation is reduced by 15 %. In Holland tests have been carried out comparing different slopes in the manure alley and frequency of scraping.

What can be done?

The main goal is to reduce the dirty surface per cow and to keep the animals clean. Stanchion barns in general have less dirty areas than cubicle sheds do. In stanchion barns a number of details need to be considered: correct measurement of the stanchion, stalls correctly adjusted, design of the feed alley, partitions between cows, management routines, barn climate, feeding, etc. In loose housing systems the hygiene in scraped alleys can be improved by adding rubber to the scraper blades, by scraping more frequently and by designing and rebuilding, making the alley slope to the center and providing them with efficient urine drainage.

What are the costs for these measures?

The costs for these measures are very difficult to predict as they vary considerably, depending of the conditions in each case.

The influence of scraping frequency and sloope of the floor on solid floors in a Dutch study:

Slope and scraping frequency

Reduction of ammonia evaporation, %

Solid floor, scraping 12 times per 24 hours

0 (baselevel)

Solid floor, scraping 96 times per 24 hours

5

Solid floor, 3% slope to one side, scraping 12 times per 24 hours

21

Solid floor, 3% slope to one side, scraping 96 times per 24 hours

26

Solid floor, 3% slope to the center, scraping 12 times per 24 hours

50

Solid floor, 3% slope to the center, scraping 12 times per 24 hours, cleaning with 6 litres of water per cow and day

65

Feeding

Measure: Analyzing the forage and preferably the grain

Why are ammonia losses reduced?

By analyzing the nutritional content, such as the crude protein, NDF, energy, and starch (grain), of the feedstuff, we get more precision in the ration formulations. We can control the amount of feed offered more efficiently and, thereby, minimize the losses of ammonia.

Where is this measure suitable?

In all dairy herds.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

By improved control of the feed offered, the nitrogen in the ration is utilized more efficiently and the nitrogen utilization by the dairy cows is improved. The sustainability in farming is improved by lower losses of nitrogen in feces and urine by ammonia emissions, which decrease the acidification in the surrounding environment and eutrophication of the water sources.

How much are ammonia losses reduced?

It is difficult to estimate the decrease of ammonia losses that can be done by analyzing the feedstuff because there are a few other factors, such as the composition of the ration, feeding routines, and lactation stage that also influence the losses. Generally, we can conclude that if the ration formulation is controlled by feed analyses and with regard to feeding routines and lactation stage, the farmer has used all possible tools on the farm to decrease the losses of ammonia. Swedish investigations show that it is realistic to have about 12-13 kg of nitrogen in manure per 1000 kg of milk from a cow per year (Gustafsson, 2000).

What can be done?

Take representative samples during the forage harvest and send them to a feed lab for analysis of dry matter, crude protein, NDF, and energy*. It also is desirable to sample the grain during harvest and have it analyzed for crude protein, energy, starch and NDF. Additionally, there will be calculated values for amino acids absorbed in the intestine, protein balance in the rumen, effective protein degradation (tabulated value), and effective fiber degradation. Use these analyses and calculated values as a basis for ration formulations on the farm.

What are the costs for this measure?: A fresh forage sample, including the analyses mentioned above, costs about 350 SEK, (38 euro, 52 USD) whereas a grain sample costs about 375 SEK (41 euro, 55 USD).

*Reference: Provtagning och Analys av Foder. Kvalitetssäkrad Mjölkproduktion. T2686-13. SHS Butiken, Svensk Mjölk.

Measure: Decreasing the crude protein content of the ration

Why are ammonia losses reduced?

Traditionally, there has been an overfeeding of protein in many dairy herds in order to have a wide margin against factors that affect the crude protein concentration but cannot be adjusted for in the ration formulations. As a result, the amount of nitrogen in the feed that is not used for milk production, growth, and pregnancy, but is excreted in feces and urine, has become relatively high. Because there is a clear correlation between the crude protein concentration of the ration and the amount of nitrogen in the feces and urine, decreased crude protein concentration is an effective method to improve nitrogen utilization by and decrease ammonia losses from Swedish dairy cows.

Where is this measure suitable?

First and foremost in all dairy herds that have high protein levels, over 18% crude protein of DM during early lactation, but also on farms with 17-18% crude protein in early lactation and have a good control of feeding and follow-up of milk yield and milk quality. It also is important to keep the protein level low for middle- and low-producing cows that often consume excess protein.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?:

A decreased crude protein concentration by one percentage unit can improve the nitrogen utilization (nitrogen in milk/nitrogen in feed) of a cow by 1.5 to 2.0 percentage units (Gustafsson, 2000). An average nitrogen utilization between 28 and 30% on an annual basis seems to be a realistic level for a dairy cow. Farming becomes more sustainable on a long-term basis through decreased risk of acidification of lakes and soils and decreased eutrophication of our water sources due to lower ammonia losses from dairy farms.

How much are ammonia losses reduced?

A decrease of the crude protein concentration by one percentage unit in the dietary dry matter is estimated to decrease the amount of nitrogen in feces and urine by 11 kg per cow each year. A decreased dietary crude protein concentration by one to two percentage units may decrease the annual ammonia losses by 500 to 1700 tonnes of ammonium-nitrogen in Sweden (Gustafsson, 2000).

What can be done?

Decrease the crude protein concentration stepwise and follow up with milk yield and milk protein percentage. In this way you will find a protein level in the ration that improves the nitrogen utilization without decreasing the milk production.

What are the costs for this measure?

Naturally, there will not be any costs associated with a decrease in the dietary crude protein concentration as long as the milk yield is maintained. The feed costs will be lowered because the proportion of protein concentrate in the ration can be decreased.

Measure: Decreasing the proportion and improve the utilization of rumen degradable protein in the ration

Why are ammonia losses reduced?

The feed protein that is degraded in the rumen into ammonia can be used for the microbial protein synthesis only in the presence of available energy that is produced in the rumen during fermentation of fiber (NDF and pectin) and starch. In the absence of energy, the ammonia will be lost in the manure. If the proportion of rumen degradable protein is decreased, the ruminal ammonia production and, consequently, the ammonia losses will decrease.

Where is this measure suitable?

On farms that use early-cut forage or have a large proportion of legumes in the sward.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Because a larger proportion of the crude protein passes the rumen without being degraded when the proportion of rumen degradable protein is decreased, nitrogen utilization and milk production will increase. Formulating the ration with NDF and starch results in a better utilization of the ammonia produced in the rumen and, thereby, a better nitrogen utilization. The sustainability of agriculture is improved by decreased ammonia emissions from dairy herds. This results in decreased acidification of the environment and decreased eutrophication of lakes, rivers, and creeks.

How much are ammonia losses reduced?

How much the ammonia losses will decrease depends on the size of the initial proportion of rumen degradable protein and how efficiently we use the ammonia that is produced in the rumen by supplementing with feedstuffs rich in fiber or starch and follow up of the feeding routines on the farm.

What can be done?

The proportion of rumen degradable protein can be decreased in the long term by altering the composition of the ley through the use of different forage species and in the short term by nitrogen fertilization. You can decrease the proportion of clover in a grass/clover ley by increasing the nitrogen fertilization application rate. The rumen degradable protein can be utilized better for the microbial synthesis if the ration is formulated with feeds rich in fiber and starch, such as whole-crop small grain silage and maize silage. The proportion of rumen degradable protein in the ration will cover the need for the microbial synthesis in the rumen. Several international investigations show that the concentration of rumen-degradable protein should be 10-11.5% of the dietary DM, which agrees with the recommendations by Lindgren (1997).

What are the costs for this measure?

The costs are not particularly large but involve a change of crop rotation to include whole-crop small grain silage and maize silage. There will be added costs for nitrogen fertilizing the ley and changing the forage seed mixture.

Reference: Lindgren, E. 1997. LFU-systemet för värdering av foder till mjölkkor. Stencil. Lantmännen Foderutveckling AB. Sverige.

Manure storage and spreading

Measure: Covering the storage

Why are the ammonia losses reduced?

The contact between the slurry in the store and the surrounding atmosphere is reduced as well as the exchange of air over the surface.

Where is this measure suitable?

Storage for slurry and urine.

How is the nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of the direct losses of ammonia from the storage during the storage period.

How much are the ammonia losses reduced?

During the storage period the losses are expected to be reduced 50 - 95% depending of which kind of cover is used.

What can be done?

A floating crust is normally established on slurry from milk cows, especially when straw is used as bedding material. In order to be efficient the crust must cover the entire store and be stable enough. In some cases solid manure, straw or peat has been added, the slurry has been mixed and the added material has formed a good crust. Sometimes leca-pebbles or floating plastic cover are used. Note that straw is best suited for slurry from cows. Used in urine stores the straw becomes wet and sinks to the bottom. Leca-pebbles are the opposite, they stay floating on thin slurry and urine, but mix easily with thick manure.

Another type of cover is a different kind of roof built on the store, sometimes resting on a central pole. The cover can be built in concrete or made of a lighter construction. It should in any case be as tight as possible.

What are the costs for this measure?

The lifetime of a cover varies, which means that its depreciation time varies as well. Floating crusts may also require additional work.

 

Kind of cover

Yearly cost SEK/m3 (euro/m3, USD/m3)

Floating crust

*

- chopped straw, peat

5-13* (0.5-1.5, 0.75-2)

- leca-pebbles

14 (1.5, 2)

- floating plastic cover

20 (2.2, 3)

Fixed roof

25-40 (2.7-4.4, 3.7-6)

* cost for manpower to be added

Measure: Choosing the right spreading technique

Why are ammonia losses reduced?

By direct injection or incorporation of the slurry into the soil directly after spreading, or alternatively by using drop boom in growing crops the ammonia is the better protected than when spread on the surface. In the soil the nitrogen is bound to the soil and a growing crop stops blowing winds. This is very important in warm, dry and windy weather.

Where is this measure suitable?

Many injection devices are suitable for spreading on grassland after e.g. the first cut. Drop boom is preferred when spreading in growing crops, 10-15 cm high, but also reduces the losses when spreading on stubble-field. Plowing or harrowing directly after other types of spreading is recommended.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of direct losses of ammonia at spreading. Furthermore unpleasant smell is reduced and the control of spread amount and accurancy is improved.

How much are ammonia losses reduced?

Direct injection or quick incorporation into the soil are the most efficient ways to reduce ammonia losses. By using these methods the ammonia losses can be reduced by as much as 80-95% compared with traditional surface spreading. Drop boom can reduce the losses by 30-50% compared with traditional techniques. The effect, however, depends on a number of other factors, such as weather, soil type, crop, time of the year, etc.

What can be done?

To incorporate the slurry into the soil directly after spreading does not normally require additional investment but does need careful planning and possibly more personnel. Technique for injection or drop boom means additional investment but can be solved by using a Contractor.

What are the costs for this measure?

A drop boom instead of a traditional surface spreader costs in the range of SEK 120,000 (13,000 euro, 17,800 USD). Equipment for injection costs about SEK 200,000 (22,000 euro, 30,000 USD). Price and design can vary a great deal between different suppliers. Using a contractor or working together with other farms might reduce the total cost considerably.

Measure: Choosing the right spreading time

Why are ammonia losses reduced?

Weather conditions such as air temperature, air moisture and wind speed have a strong influence on the amount of losses.

Where is this measure suitable?

At all times when manure is to be spread on surface by traditional spreading or by drop boom. Choosing the right spreading time also include other concerns such as the risk for tracks in the growing crops, leaking or runoff, delaying other jobs etc. It is very difficult to optimize all these parameters at the same time.

How is nitrogen efficiency and the sustainability of your farm affected by this measure?

Reduction of the direct losses when spreading.

How much are ammonia losses reduced?

Losses can easily be reduced by 50%. As weather parameters can vary within wide ranges ammonia losses can vary accordingly. Best effect is achieved at low temperature, high humidity and low wind speed.

What can be done?

Plan spreading in two steps. Crop rotation and size of storage determine when during the year the manure should be spread. From the ammonia losses point of view early spring, spring or even late autumn is preferred to spreading during the summer. When the period for spreading approaches, be sure to follow the weather forecasts and avoid spreading on warm, dry and windy days. If possible try to spread just before rain.

What are the costs for this measure?

In many cases this is a matter of planning the work, but in some cases changes in the plan can lead to increased risk for soil compaction during the spring and spreading in growing crops means more expensive equipment.

Project figures for cost are from 2003.

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