Low N loss from a bedded pack barn with

intensive composting of a woodchip bedding

EAAP 2015, Warsaw, Poland

Herman de Boer, Paul Galama, Hendrik Jan van Dooren

Why determine level of N loss from a barn?

In the Netherlands: legislation limits N input at farm level and the

allowed level of gaseous NH3 loss from a barn

With restricted N input, a high gaseous total N loss (as NH3, N2O,

NOx, N2) results in a declining agricultural and financial productivity

New barn types have to meet criteria to limit NH3 loss, otherwise

barns are not allowed to be built

Bedded pack barns (loose housing + actively managed organic

bedding) are new in the Netherlands. Information on the level of total

N loss and NH3 loss from these barns is therefore required

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How to determine N loss from a barn?

We did it by calculation of barn N balances:

N balance = Nlitter + Nfeed – Nmilk – Nliquid manure – Nbedding – Nanimal tissue

We also calculated supportive barn P and K balances. Differences on

the barn P and K balance indicate the level of error (systematic +

random) of the balance calculation/measurements. We used this

information to correct N balances for a more reliable calculation of N

loss

NPK balances were calculated for individual commercial dairy farms.

Data were collected/measured at the farms and provided by the

farmers

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Differences between barns can affect level

of N loss

Bedded pack barns differ in:

● Type of bedding material (woodchips, shredded wood, municipal compost, straw)

● Management (composting, litter addition only, type/frequency of cultivation, etc.)

● Intensity of use (m2/animal), relative area of bedding and hard flooring

● Type of mechanical ventilation (none, air blowing, air suction)

● Etc.

Differences between barns can result in differences in level of total N

loss

We calculated N balances and total N loss for six different bedding

pack barns, for a period of 0.5 up to 1 year, in 2011/2012

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Range in N loss for six bedded pack barns

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19%

35%

40% 40%

44%

63%

0%

10%

20%

30%

40%

50%

60%

70%

1 WC 3 WC 4 WC 5 WC 8 GWC 9 GWC

Gas

eo

us

N lo

ss (

% o

f N

exc

rete

d o

n t

he

bar

n f

loo

r)

Barn code

WC = wood chips

GWC = green waste compost

In search of management practices to

reduce N loss from the bedded pack barn

We observed large differences in N loss from different barns;

relatively low N loss from barns with composting of woodchips

Knowledge on development of N loss over time, especially in relation

to bedding characteristics & management practices, may be used to

control and reduce N loss

Therefore, we started research to determine the development of N

loss over time, in relation to bedding characteristics & management

Two different barns with composting of wood/woodchips:

● Intensive composting at 50-55°C (woodchips)

● Passive composting at 35-40°C (shredded wood)

Calculation of NPK balance and N loss every 2-3 weeks for a period of

8 to 11 months, including winter period, in 2013/2014

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Some differences in management between

intensive/passive composting

Intensive composting:

● Fresh woodchips, C/N >70; frequent supply of new chips to bedding

● Intensive daily cultivation/mixing with rotary tiller, up to 30 cm deep (40/50 cm deep bedding)

● Mechanical ventilation by short bursts of air blowing (15 minutes every 6 hours)

Passive composting:

● Course wood parts (shredded wood), C/N ~ 40; low supply of new litter

● Little daily cultivation and mixing with a digging machine/tine cultivator up to 30-40 cm deep (60/70 cm deep bedding)

● Mechanical ventilation by air suction when temperature exceeded 32/35°C (50% of the balance time)

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Low N loss with active composting

8

-30

-20

-10

0

10

20

30

40

50

60

70

2-11-13 12-12-13 21-01-14 2-03-14 11-04-14 21-05-14 30-06-14 9-08-14 18-09-14 28-10-14

N lo

ss (

% o

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Date

Active composting Passive composting

Intensive composting: strong relationship

between development of N loss and C/N ratio (1)

9

0

10

20

30

40

50

60

70

-25

-20

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13-11-13 13-12-13 13-01-14 13-02-14 13-03-14 13-04-14 13-05-14 13-06-14 13-07-14

C/N

rat

io b

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din

g

N lo

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% o

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Date

N loss C/N ratio bedding

Intensive composting: strong relationship

between development of N loss and C/N ratio (2)

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N loss (%) = 0,1767 - 0,005176 * C/NP < 0,001; R² = 87%

-25

-20

-15

-10

-5

0

5

10

0 10 20 30 40 50 60 70

N lo

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% o

f N

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C/N ratio bedding

Some differences in management between

intensive/passive composting

Intensive composting:

● Fresh woodchips, C/N >70; frequent supply of new chips to bedding

● Intensive daily cultivation/mixing with rotary tiller, up to 30 cm deep (40/50 cm deep bedding)

● Mechanical ventilation by short bursts of air blowing (15 minutes every 6 hours)

● N loss from the bedding reduced by incorporation of excreted N in bacterial biomass during composting

Passive composting:

● Course wood parts (shredded wood), C/N ~ 40; low supply of new litter

● Little daily cultivation and mixing with a digging machine/tine cultivator up to 30-40 cm deep (60/70 cm deep bedding)

● Mechanical ventilation by air suction when temperature exceeded 32/35°C (50%

of the balance time)

● Most of the excreted N on the bedding volatilized

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Conclusions

There are large differences in N loss between bedded pack barns with

different forms of bedding characteristics & management; N loss from

composting woodchip/shredded wood beddings are relatively low

The lowest N loss was measured for a barn with active composting of

woodchips: the level of N loss was equal/lower than N loss of a

reference free stall barn in the Netherlands

N loss during active composting was strongly related to C/N ratio of

the bedding; frequent supply of fresh woodchips supressed N loss

The relationship between N loss and C/N ratio suggests potential to

realize a very low N loss when C/N ratio is maintained above a

threshold level (~35)

Bedded packs barns have potential to realize a low level of total N

loss, and consequentially also a low NH3 loss, from the barn

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The end

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