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Narbon bean response to fertiliser nutrients in the Victorian Mallee

C.A. Bell1, C.J. Korte2, C. Heazlewood1, G.H. Castleman1, V.J. Matassa2

1 Agriculture Victoria – Walpeup, Victorian Institute for Dryland Agriculture, Walpeup, Victoria.
2 Agriculture Victoria – Horsham, Victorian Institute for Dryland Agriculture, Horsham, Victoria.

ABSTRACT

To develop agronomic recommendations for the new crop narbon bean (Vicia narbonensis), the response to fertilisers applied at sowing was measured in the Victorian Mallee at Walpeup. Responses to six rates of phosphorus (P) application were assessed over three years and combinations of phosphorus, nitrogen (N), sulphur (S) and zinc (Zn) fertiliser were assessed over four years. Measurements included grain yield, thousand grain weight and grain protein, S and gamma-glutamyl-S-ethenyl cysteine (GEC) concentrations. Phosphorus application significantly increased grain yield and thousand grain weight, but decreased grain S and GEC concentrations. Nitrogen application significantly increased grain yield and reduced S and GEC concentrations in grain. Sulphur applications increased GEC concentrations. Zinc applications had relatively little effect.

KEY WORDS

Narbon bean, Vicia narbonensis, fertiliser, gamma-glutamyl-S-ethenyl cysteine.

INTRODUCTION

Narbon bean (Vicia narbonensisis L Var. narbonensis) is a new crop that has been developed for medium to low rainfall regions of Australia with soils of neutral to alkaline pH. Features of narbon bean include an erect growth habit, a tap root system and good resistance to disease and insects. Grain of narbon bean contains the amino acid gamma-glutamyl-S-ethenyl cysteine (GEC) at sufficiently high concentrations (0.1-3%) to reduce palatability to monogastrics (2, 6). The crop could play a valuable role in rotations because of its multiple end uses including grain, grazing, conserved fodder and green manure, and because it is not a host to the cereal diseases cereal cyst nematode and take-all. Siddique et al. (6) and Thomson et al. (7) reported phenology, growth and grain yields of narbon bean accessions in low rainfall areas of south-Western Australia, however little is known of the responses of narbon beans to fertilisers.

Results from fertiliser experiments undertaken to develop agronomic recommendations for narbon bean are reported in this paper. Experiments evaluated the effect of fertilisers on grain production and concentrations of protein, S and GEC in grain. The experimental aim was to increase grain yield and protein with fertilisers, while decreasing GEC concentrations.

MATERIALS AND METHODS

Experiments were conducted over four years (1996-1999) at the Mallee Research Station, Walpeup on a Walpeup sandy loam, a Calcic Calcarosol (3). Growing season rainfall (April-October) for 1996, 1997, 1998 and 1999 was 221 mm, 168 mm, 190 mm and 198 mm respectively (long term average 225 mm). Annual rainfall was below average in all years except 1996 when average rainfall was received. Australian Temperate Field Crops Collection accession ATC 60105 was used in the 1996-1998 experiments and cv Tanami was used in 1999. Experimental sites had medic pastures for the two preceding seasons.

Three experiments (1996-1998) were conducted to evaluate the response of narbon bean to phosphorus (P) applied as superphosphate at sowing time at rates equivalent to 0, 5, 10, 20, 30 and 40 kg P/ha. All experiments were designed as randomised complete blocks with four replications. Plots were 1.4 m (8 rows) by 15 m. Gypsum was used to adjust S input to a common rate of 6.5 kg S/ha.

Four experiments (1996-1999) evaluated the response of narbon bean to zinc (Zn), nitrogen (N) and sulphur (S) fertilisers applied at sowing with P fertiliser (18 kg P/ha). All experiments included the 8 factorial combinations of Zn (0 and 2.5 kg Zn/ha as zinc oxide), N (0 and 15 kg N/ha as urea or ammonium sulphate) and S (0 and 20 kg S/ha as sulphate), plus a control treatment (no P, Zn, N, or S), arranged in a randomised complete block design with four replicates. Plots were 1.4 m (8 rows) by 15 m.

Soil test results for experimental sites are shown in Table 1. Grain measurements included: yield, weight, protein (estimated as 6.25 x N), S and GEC. GEC was measured using capillary electrophoresis (2).

Table 1. Pre-sowing surface soil (0-10cm) Colwell phosphate (mg/kg), pH (1:5 CaCl2) and nitrate N (mg/kg) in different experiments.

Experiment

Colwell P

pH

Nitrate

P rate

     

1996

9

6.1

8

1997

15*

6.0

13

1998

15

5.6

18

Factorial

      

1996

10

7.0

10

1997

15*

6.2

11

1998

23

5.8

22

1999

17*

6.6

-

* Colwell P estimated from Olsen P measurement

Results were analysed using analysis of variance, where the data were combined across years. In the P rate experiments, orthogonal polynomials were used to investigate the relationship between rate and response. In the factorial experiments, the control treatment (no P, Zn, S or N) was excluded from the analysis of variance. The effect of P in the factorial experiments was obtained by comparing the control treatment (no P, Zn, S or N) with the treatment that received P but no Zn, S or N.

RESULTS

Phosphorus rate

Grain yield increased significantly (P<0.05) with P rate up to 30 kg P/ha (60% compared with the control), with the relationship between P application rate and grain yield having a quadratic response profile (Table 2). Grain size was not significantly affected by P application. Grain protein increased with P application rate, the linear effect being statistically significant (P<0.05). Phosphorus application decreased both GEC and S concentrations in the grain, with the relationships between P application rate and GEC or S concentration having statistically significant (P<0.05) linear and quadratic terms.

Table 2. Effect of phosphorus (P) rate on grain yield, grain weight and concentrations of protein, GEC and sulphur in grain. Values are combined means from 1996-1998.

P rate
(kg/ha)

Grain yield
(kg/ha)

Grain weight
(g/1000 seeds)

Protein
(%)

GEC
(%)

Sulphur
(%)

0

433

18.6

26.7

2.13

0.36

5

579

18.3

26.4

1.80

0.31

10

622

18.0

26.7

1.83

0.32

20

629

17.8

26.6

1.80

0.30

30

693

18.2

27.2

1.63

0.29

40

583

18.1

27.3

1.69

0.31

LSD (P=0.05)

154 *

1.0 n.s.

0.57 *

0.12 ***

0.02 ***

*** P<0.001, * P<0.05, n.s. not significant.

Factorial experiments

Grain yield was significantly (P<0.05) increased by application of P (34%) and N (8%), but not by application of S or Zn (Table 3). For grain yield there were no significant interactions between N, S or Zn.

Grain weight was significantly (P<0.05) reduced by application of P (5%), but there were no other treatment effects on grain weight (Table 3). Grain protein was not significantly affected by the fertiliser treatments.

Sulphur application increased GEC by 8% and S concentrations by 10% (Table 3). Phosphorus application had no statistically significant (P<0.05) effect on GEC and S concentrations. The N by Zn interaction was statistically significant (P<0.05) for both GEC and S concentrations. Zinc application increased GEC concentration when no N was applied, but had no significant (P<0.05) effect when N was applied (means for N-Zn-, N-Zn+, N+Zn-, N+Zn+ respectively 1.52%, 1.64%, 1.51%, 1.52%; LSD 0.07%). A similar pattern occurred for S concentration.

Table 3. Effect of phosphorus, nitrogen, sulphur and zinc on grain yield, grain weight and concentrations of protein, GEC and sulphur in grain. Values are combined means from 1996-1999.

 

Grain yield
(kg/ha)

Grain weight
(g/1000 seeds)

Protein
(%)

GEC
(%)

Sulphur
(%)

Phosphorus

          

-

399

18.9

24.1

1.58

0.31

+

534

17.9

24.4

1.54

0.30

LSD (P=0.05)

28 ***

0.24 **

0.19 n.s.

0.04 n.s.

0.01 n.s.

Nitrogen

          

-

568

17.8

24.4

1.58

0.31

+

611

17.9

24.3

1.52

0.30

LSD (P=0.05)

32 *

0.14 n.s.

0.12 n.s.

0.04 *

0.01 **

Sulphur

          

-

591

17.9

24.4

1.49

0.29

+

588

17.8

24.3

1.61

0.32

LSD (P=0.05)

32 n.s.

0.14 n.s.

0.12 n.s.

0.04 ***

0.01 ***

Zinc

          

-

584

17.8

24.4

1.52

0.30

+

595

17.9

24.3

1.58

0.31

LSD (P=0.05)

32 n.s.

0.14 n.s.

0.12 n.s.

0.04 *

0.01 **

*** P<0.001, ** P<0.01, * P<0.05, n.s. not significant, Significant N x Zn interaction.

DISCUSSION

The aim of this research was to identify nutrients that could increase grain yield and protein concentration of narbon bean, while decreasing GEC concentration. Phosphorus application increased grain yields by up to 60%, grain protein by up to 2% and reduced the GEC concentration of grain by up to 20% (Table 2). By contrast, S application had no beneficial effect on grain yield or protein and increased the concentration of GEC in grain (Table 3). Nitrogen application partially met the experimental aim, increasing grain yield, but only reducing GEC concentration significantly when applied with Zn. In these experiments Zn application had no significant beneficial effect on grain yield or protein, but increased GEC concentration when N was not applied. Based on these results, it is concluded that P is the most important fertiliser nutrient required for growing narbon beans at the Mallee Research Station, with N ranked next most important. These experiments indicate S and Zn fertiliser have the potential to reduce narbon bean grain quality through increasing GEC concentration of grain.

Yield responses of cereal crops to P application on Mallee soils have been well established (1, 5), so some yield response of narbon beans to P application was expected. An application of 10 kg P/ha largely satisfied the requirement for P (Table 2), with higher rates resulting in smaller increases in yield. Grain protein concentration was increased by P fertiliser application probably because of improved P nutrition and because P increased nitrogen fixation activity. In 1998 P application resulted in higher numbers of nodules on narbon bean roots, larger nodules and a higher proportion of effective nodules (J. Slattery, pers. comm.).

Extrapolation of P fertiliser responses found in these experiments to farms in the Mallee region is limited because of the wide range of nutrient status found under commercial conditions, the wide range of soil types, and variation in other factors that influence grain yield responses to P such as growing season rainfall. The mean Colwell P test of experimental sites in Table 1 was 15 mg/kg (approx. Olsen P 8 mg/kg). Survey data collected from Mallee paddocks in 1993 (J. Slattery, pers. comm.) indicate that a large percentage of paddocks have a similar P status to experimental sites (15%, 55% and 30% respectively in the ranges Olsen P 1-6, 7-12, >12 mg/kg). It is therefore concluded that Mallee farmers can expect narbon bean yield to respond to P fertiliser at sowing, with possibly larger responses where P status is lower than the experimental sites.

In these experiments narbon bean was inoculated with the currently recommended commercial rhizobia strain (field pea inoculant SU303). This rhizobia strain has been found in glasshouse experiments to be less effective than other non-commercial strains (J. Slattery, pers. comm.). Increased grain yield in response to N application was probably a reflection of lack of rhizobia effectiveness.

Changes in S and GEC concentrations in grain with fertiliser applications reflected changes in availability of S and dilution of available S. Sulphur application presumably increased S and GEC concentrations through increased S availability and uptake by narbon beans. Phosphorus and N applications resulted in larger increases in grain yield than grain S uptake, causing a reduction in S and GEC concentrations. For example, in the P rate experiment 30 kg P/ha resulted in 60% more grain but only 30% more grain S.

Responses to Zn application in these experiments are difficult to interpret; especially as no effective monitoring of Zn status of experimental sites or crops was undertaken. Further research is necessary before firm conclusions can be drawn regarding responses to Zn fertiliser in narbon bean.

Pulse crops grown in the Mallee are usually fertilised at sowing with 95 kg/ha of "Grain Legume Super Zinc" (3), providing 14 kg P/ha, 7 kg S/ha and 2 kg Zn/ha. This fertiliser input should meet the P requirements of narbon bean crops on soils with soil test measurements similar to the experimental sites, but not N requirements. The S input of Grain Legume Super could reduce grain quality through increased GEC concentration.

It is recommended that narbon beans be sown with adequate P and N to maximise yields, with S inputs being minimised so that grain quality is not reduced.

ACKNOWLEDGMENTS

The work reported in this paper was funded by the Department of Natural Resources and Environment and the Grains Research and Development Corporation as part of project DAV368 “Developing narbon beans as a crop for low rainfall cropping districts.” Suggestions from colleagues and referees are also acknowledged.

REFERENCES

1. Colwell J.D. 1977. National Soil Fertility Project. Vol 2. Soil fertility Relationships. (CSIRO Division of Soils: Adelaide).

2. Enneking D. 1995. The toxicity of Vicia species and their utilisation as grain legumes. (Centre for Legumes in Mediterranean Agriculture, Occ. Pub. No. 6, University of Western Australia).

3. Hall N. 2000. Mallee Gross Margins 2001-2002. (Department of Natural Resources and Environment, Victoria).

4. Isbell R.F. 1966. Australian Soil Classification. (CSIRO Publishing: Collingwood, Vic).

5. Jardine R. and Elliot B.R. 1977. Aust. J. Exp. Agr. & Anim. Husb. 17, 812-817.

6. Siddique K.H.M., Loss S.P. and Enneking D. 1996. Aust. J. Exp. Agr. 36, 53-62.

7. Thomson B.D. and Siddique K.H.M. 1997. Field Crop Research 56, 189-199.

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