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LUCERNE IN CROP ROTATIONS

P. Egan1, J. Hulme3, K. P. Ransom1 and D. Whitfield2

1 Department of Natural resources and Environment, Bendigo, 3554. 2 Institute For Sustainable Irrigated Agriculture, Tatura, 3616. 3 Mallee Research Station, Walpeup, 3507

Abstract

This paper describes effect of lucerne versus annual medic based pasture on soil parameters and wheat production after one year of pasture. Data are presented from two sites in Northern Victoria. Prior to cropping pasture treatments were phosphate versus no phosphate and continuous grass control versus nil grass control before cropping.

Keywords: lucerne, wheat, annual pasture

A lucerne phase in crop rotations potentially benefits grain yield and protein and the profitability of grazing enterprises. Sites were established at Glenloth and Walpeup to appraise the effects of lucerne on soil conditions and subsequent crop growth and yield in Northern Victoria. Cropping following lucerne will conclude in 2000.

Method

Pasture treatments were established at Glenloth (36.100S, 143.400 E) and at Walpeup (35.100S 142.000E) in 1995. Treatments at both sites were a 2 x 2 x 2 factorial combination of ; 1) Pasture type - Lucerne v Annual; 2) Pasture nutrition - Nil P v P (10 kg phosphorus/ha/year as superphosphate in winter); and, 3) Grass control - Nil v Fusilade (500 ml/ha/year in winter). Treatments were laid out in a randomised block design of 3 replications, and were subjected to first and second wheat crops (C1P1 and C2P0) in 1997 following the first crop, C1P0, in 1996.

Crops (CcPp) are referenced by year of cropping (c) following years of pasture (p).

Wheat crops, C2P0 and C1P1, were completed in 1997. Plant measures included tissue %N and biomass (BM) at development stages Z30, anthesis and maturity, spike number at anthesis and maturity, and kernel size, kernel number, grain protein and grain yield at maturity. Soil measures included P, PO4, Total N, NH4-N, Organic Carbon and NO3-N in the surface (0 - 0.1 m) at sowing, and NH4-N and NO3-N to 1.3 m at Z30, anthesis and maturity. Available N (Av. N) was calculated as the sum, NO3-N + NH4-N.

Results and discussion

Glenloth

Table 1. Effect of pasture type on wheat growth and yield at Glenloth

Crop C2P0

Crop C1P1

Parameter

Annual

Lucerne

LSD

Annual

Lucerne

LSD

%N

Z30

1.67

1.82

ns

1.62

1.96

0.29 *

BM

(g/m2)

Z30

52

63

ns

68

104

25.0 *

Plant N

(g/m2)

Z30

0.87

1.15

ns

1.09

2.09

0.66 **

%N

anth.

1.04

0.90

ns

1.02

1.25

0.22 *

BM

(g/m2)

anth.

155

170

ns

178

256

41 **

N

(g/m2)

anth.

1.65

1.53

ns

1.84

3.31

0.88 **

spikes

(/m2)

anth.

185

192

ns

167

185

ns

Yield

(t/ha)

Mat.

0.80

0.81

ns

0.75

0.70

ns

Soil measurements in C1P1, made at sowing following one year of pasture, showed a significant accumulation of available N confined to the surface soil (0 - 0.1 m) following lucerne (P<0.01): there were no significant effects on organic carbon or total N in the soil. The increase in available N attributable to lucerne (16.2 ppm) equated to approx. 25 kg N/ha, and was associated with significant increases in 1) tissue N concentration, 2) wheat biomass, and 3) crop N accumulation at both Z30 and anthesis. However, there were no commensurate effects on spike production and yield, presumably because of overriding seasonal conditions.

Table 2. Effect of pasture type on available N (ppm), total N (%) and organic carbon (%) at Glenloth

Crop C2P0

Crop C1P1

Parameter Depth (m)

Annual

Lucerne

LSD

Annual

Lucerne

LSD

Av. N

(0 - 0.1)

sow

7.4

7.1

ns

10.4

26.6

10.7 **

(0.1- 0.3)

sow

4.0

3.4

ns

4.3

4.6

ns

(0.3- 0.7)

sow

2.4

2.3

ns

2.7

2.8

ns

(0.7- 1.0)

sow

1.5

1.5

ns

2.6

2.7

ns

(1.0- 1.3)

sow

1.6

1.3

ns

2.1

2.1

ns

total N

(0 - 0.1)

sow

0.078

0.082

ns

0.087

0.094

ns

Org. C

(0 - 0.1)

sow

0.97

0.96

ns

0.91

0.94

ns

Walpeup

N concentration of the vegetative plant material at Z30 was much greater at Walpeup than seen at Glenloth, suggesting that N supply at Walpeup was more attuned to constricted growth demands mediated by availability of water. The greater tissue N concentration at Walpeup was achieved at the expense of growth. The slight depression in yield caused by Lucerne in Crop C1P1 at Walpeup (P<0.05) remains unexplained at this stage.

Table 3. Effect of pasture type on wheat growth and yield at Walpeup

Crop C2P0

Crop C1P1

Parameter Units

Annual

Lucerne

LSD

Annual

Lucerne

LSD

Plant measures

N

(%)

Z30

4.05

3.80

ns

4.72

4.45

ns

BM

(g/m2)

Z30

17.4

21.0

ns

22.3

25.0

ns

Plant N

(g/m2)

Z30

0.69

0.79

ns

0.90

0.94

ns

Yield

(t/ha)

Mat.

0.77

0.72

ns

0.64

0.49

0.11*

Table 4. Effect of pasture type on available N (ppm), total N (%) and organic carbon (%) at Walpeup

Crop

C2P0

Crop

C1P1

Parameter

Depth (m)

Annual

Lucerne

LSD

Annual

Lucerne

LSD

Av. N (

(0 - 0.1)

sow

7.2

9.1

ns

12.7

12.5

ns

(0.1- 0.3)

sow

4.0

4.2

ns

3.0

4.5

ns

(0.3- 0.7)

sow

1.5

1.5

ns

1.8

1.2

ns

(0.7- 1.0)

sow

3.4

5.2

ns

3.8

3.3

ns

(1.0- 1.3)

sow

6.1

5.7

ns

4.6

5.4

ns

total N

(0 - 0.1)

sow

0.048

0.043

ns

0.046

0.043

ns

Org. C

(0 - 0.1)

sow

0.48

0.46

ns

0.57

0.54

ns

Conclusions

Wheat growth benefited following one year of lucerne pasture through increased N but this was not seen in improved yields. Future crops will determine the extent to which lucerne can effect grain growth and yield.

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