Results of Long-Term Experiments

With Conservation Tillage in Austria

Introduction

On-site and off-site damages of soil erosion cause serious problems in Austria. Successful soil conservation measures are needed to reduce these threats and to improve soil quality.

In a long-term field experiment in Lower Austria three soil management systems were investigated to evaluate the impact of tillage practices on runoff, soil loss, nutrient losses, crop yield and overall soil quality.

Since three years also the impact of these management systems on soil CO2 efflux and carbon dynamics was investigated.

Materials and Methods

Site Mistelbach Pixendorf Pyhrasoil texture silt loam silt loam loamsand (%) 8 19 38silt (%) 65 61 39clay (%) 27 20 23

slope (%) 12-13 5-6 15-16annual precip. (mm) 645 687 947

mean ann. temp. (°C) 9.6 10.4 9.4

Tab. 1: Main characteristics of the field sites

Fig. 1: Location of the study sites

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Erosion plots (4m x 15m) were installed to monitor surface runoff and soil loss as well as nutrient and pesticide losses. In 2002 and 2003 soil water content was continuously monitored in the root zone using FDR sensors. Each year crop yield was determined.

Fig. 3: Infra-red gas analyzer+soil respiration cham-ber; temperature probe

The field experiments were started in 1994 at three sites in Lower Austria (Fig. 1 and 2). A crop rotation of corn – small grains was applied. Soil textures ranged from silt loam to loam (Tab. 1). The following tillage systems are investigated:

1) Conventional tillage (CT)

2) Conservation tillage with cover crop during winter (CS) and reduced tillage (RT), respectively

3) Direct seeding with cover crop during winter (DS) and no-tillage (NT), respectively. Fig. 2: Erosion plots at Pixendorf

Surface Runoff and Soil Erosion

Results show that impact of tillage practice on surface runoff differs between soil textures (Fig. 4). Reduced tillage intensity (CS and DS) decreases infiltration for heavy soils (by compaction) but increases infiltration for lighter soils (like silt loam).

CT and DS reduce soil loss significantly at all sites (Fig.4). Long-term reductions range between 65% for CT and 83% for DS.

Event based soil loss depends on tillage system which is highly correlated to soil cover. Fig. 5 shows erosion rates for single storm events related to storm erosivity.

Erosion rates from CS and DS are on average one order of magnitude smaller that rates from CT. Large distribution depends on soil surface condition at time of erosive event (bare soil vs. completely covered).

Results

For soil CO2 efflux determi-nation a portable soil respira-tion system (Fig. 3) is used. These measurements were carried out once a week.

A. Klik1), G. Trümper1), and J. Rosner2)

0,0

0,1

1,0

10,0

100,0

1000,0

0,0 0,1 1,0 10,0 100,0 1000,0

E I30 (kJ.m-2.mm.h-1)

So

il L

oss

(t/

ha)

CT CS DS

Fig. 5: Relationship between event based rainfall erosivity and soil loss

Nutrient, carbon and pesticide losses

Losses of nutrients (nitrogen and phosphorus), organic carbon and pesticides were mainly influenced by amount of soil loss (Fig. 6).

Pesticide losses are function of time interval between pesticide application and the occurrence of the first erosive event. Nevertheless CS and DS can positively reduce these losses (Fig. 6)

Fig. 6 Long-term average annual losses of nitrogen, phosphorus, organic carbon and applied pesticides (1994-2009)

2,2

1,0

0,6

0

1

2

3

4

5

PesticideL

oss

es (

% o

f ap

pl.

am

ou

nt)

75,9

27,7

17,9

0

20

40

60

80

100

120

Corg

8,8

3,43,7

1,32,5

0,5

0

5

10

15

20

Nitrogen Phosphorus

Loss

es (k

g.ha

-1.a

-1)

0

20

40

60

80

100

120

Corg

Lo

ss

es (

kg.h

a-1.a

-1)

Lo

ss

es (

kg.h

a-1.a

-1)

Lo

ss

es (

% o

f ap

pl.

amo

un

t)

0

5

10

15

20

Nitrogen Phosphorus

CT CS DS

0

20

40

60

80

100

120

Corg

Fig. 4: Long-term (1994-2009) average annual runoff (left) and soil loss (right)

13,5

26,8

36,6

25,2

8,4

29,931,8

22,7

10,5

32,1

16,118,9

0

10

20

30

40

50

60

70

80

Mistelbach Pyhra Pixendorf Average

Su

rfac

e R

un

off

(m

m.a

-1)

CT CS DS

9,57

3,37

6,09 6,34

1,50 1,98

3,112,20

1,10 1,380,81 1,09

0

5

10

15

20

Mistelbach Pyhra Pixendorf Average

Soi

l Los

s (t

.ha

-1.a

-1)

CT CS DS

The measurements of soil water content (Fig. 7) show higher soil water contents in CS and DS compared to CT and therefore improved water availability for plants. In the first years after adaptation of the tillage system a slight decrease in yield must be taken into account when using CS and DS systems. After this period a trend of increasing yields can be observed (Fig. 8).

Soil Water Content and Crop Yield

2002 (corn) 2003 (winter wheat)2002 (corn) 2003 (winter wheat)

Fig. 7: Temporal and spatial distribution of soil water content for CT, CS and DS (Mistelbach site)

Pyhray = 0,0415x + 102,78

R2 = 0,0001

Mistelbachy = -0,8132x + 96,956

R2 = 0,0627

Pixendorfy = 3,5173x + 75,343

R2 = 0,389

0

25

50

75

100

125

150

175

1994 1996 1998 2000 2002 2004 2006 2008

Fig. 8: Relative average crop yields for CS and DS compared to CT

0

25

50

75

100

125

150

175

1994 1996 1998 2000 2002 2004 2006 2008

Re

lati

ve

Yie

ld (

%)

Pyhra

y = 1,2912x + 95,137

R2 = 0,1551

Mistelbachy = 0,0703x + 93,044

R2 = 0,0005

Pixendorfy = 2,3143x + 87,496

R2 = 0,2267

0

25

50

75

100

125

150

175

1994 1996 1998 2000 2002 2004 2006 2008

Re

lati

ve

Yie

ld (

%)

CS

DS

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Figure 4 shows the courses of the soil CO2 efflux in Pixendorf and Tulln from April 2007 to September 2009. The calculated carbon losses for three measuring periods are illustrated in Figure 5. The box plot in fig. 11 gives an overview of the distribution of CO2 flux data during the three years of measurements.

4.7

6.95.7

7.0 7.4

6.6 4.2

2.8 3.4

120% 148%82%121%100% 93%105%100% 100%

CT RT NT

Tulln

2007 2008 20092007 2008 20092007 2008 2009

5.4

6.67.08.4

10.4

11.1

7.7

9.1

8.4

109% 92%100% 95% 77%100% 94% 75%100%0

2

4

6

8

10

12

14

CT RT NT

carb

on

rel

ease

(t

CO

2-C

ha-1

)

2007 2008 2009

Pixendorf

2007 2008 20092007 2008 2009

Fig. 12: Resulting carbon release for Apr. - Nov. 2007, Apr. - Nov. 2008 and March - Sept. 2009

01/04/07 01/07/07 01/10/07 01/01/08 01/04/08 01/07/08 01/10/08 01/01/09 01/04/09 01/07/09 01/10/09

winter rape winter wheat barley

0.0

0.5

1.0

1.5

2.0

FC (

g C

O2

m-2

h-1

)

CT RT NT

01/04/07 01/07/07 01/10/07 01/01/08 01/04/08 01/07/08 01/10/08 01/01/09 01/04/09 01/07/09 01/10/09

maize winter wheat maize

0.0

0.5

1.0

1.5

2.0

FC (

g C

O2

m-2

h-1

)

Fig. 10: Course of soil CO2 efflux in Pixendorf (above) and Tulln (below) from Apr. 2007 to Sept. 2009

1) Institute of Hydraulics and Rural Water Management, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria

2) Government of Lower Austria, A- 3430 Tulln, AustriaContact: andreas.klik@boku.ac.at

The data indicate differences between the management practices (CT~RT>NT), but show also a high spatial variation within each plot.

The applied method only measures the overall CO2 efflux, but does not allow any determination of the carbon source. Therefore, the soil respiration data include mineralisation of soil organic carbon by microorganisms, but also root respiration and mineralisation of plant residues.

FC

(g

CO2

m-2

h-1

)

0,0

0,3

0,6

0,9

1,2

1,5

1,8TullnPixendorf

CT RT NT CT RT NT

Fig. 11: Box plot for CO2 efflux in Pixendorf and Tulln from Apr. 2007 to Sep. 2009 (indicates median, 25th/75th, 10th/90th percentile outlying points)

Conclusions Soil management systems with reduced tillage intensity combined with cover crops during winter period

improve soil hydraulic properties. CS and DS shown higher soil water contents and therefore increased water availability for plants during

growing season. Better soil water availability together with increased soil quality lead to same or higher crop yields compared to

CT. High spatial variability of soil CO2 efflux due to the dependency on several factors (e.g. soil moisture and

temperature, substrate amount, vegetation activity, soil texture) Lower soil CO2 efflux for NT than for CT; for RT no general trend visible.

Soil CO2 Efflux

Acknowledgements: This study is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management and the provinces of Lower Austria and Styria.

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