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Effect of plant density and sowing date on narrow leaf lupin production in the Victorian Mallee

A.J. Corbett 1, I.T. Mock 1 and V. Matassa 2

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

ABSTRACT

Field research conducted in 1998–1999 at the VIDA Walpeup, Mallee Research Station, investigated the effect of time of sowing and plant density on narrow leaf lupin production. Grain yield and dry matter production were consistently higher with densities of 60 plants/m2 than those achieved with 35 plants/m2. Greater responses to increased plant densities occurred when sowing was delayed beyond April. On average, an extra 0.4 tonne/ha of grain yield was produced when plant densities were increased from 30 plants/m2 to 60 plants/m2. Other benefits from increasing plant density included increased harvest height and crop residue and potentially greater residual nitrogen for the following crop. Seeding rates of 100kg/ha to 125kg/ha achieved the required 60 plants/m2 in narrow leaf lupins.

KEY WORDS

Lupin, seeding rate, sowing date.

INTRODUCTION

Narrow leaf lupins are grown in the Victorian Mallee region as a cash crop and for the residual benefits to the following cereal crop by providing a disease break and potentially increasing soil nitrogen levels.

Grain production is greater in years when seeding occurs between mid April and early May, as plants establish rapidly in warm soils. Yields decline as seeding is delayed beyond April and when plant densities are not adequate. Many Mallee farmers appear to be limiting production from narrow leaf lupin crops with observed densities as low as 30 plants/m2 and especially in seasons when seeding is delayed.

Seeding rate research conducted on narrow leaf lupin varieties of the 1970’s found that densities of 35 plants/m2 were adequate to maximise yields (1). Trials conducted in 1995 and 1996 re-evaluated this recommendation to determine suitable seeding rates for modern varieties. The study found that densities of 60 plants/m2 optimised production for the variety Merrit (4). Narrow leaf lupins appear not to compensate for low plant densities if sown later than April or in a dry seasonal finish in low rainfall environments. This study investigates the effect of time of sowing and seeding rate on lupin plant density and grain production in the Victorian Mallee.

MATERIALS AND METHODS

Field experiments conducted at the Mallee Research Station, Walpeup in 1998 and 1999 compared the effect of seven seeding rates and three times of sowing in terms of cv. Merrit dry matter production, plant number and grain yield. Seeding rates used were 25, 50, 75, 100, 125, 150 and 175 kg/ha. Sowing dates in 1998 were April 20th, May 20th and June 20th and in 1999, May 20th, June 10th and July 1st. There were 4 replicates of each treatment in both years. The data was subjected to an analysis of variance. Differences in treatment means of P<0.05 were considered to be significant.

RESULTS AND DISCUSSION

Lupin plant density increased as seeding rate increased for all three times of sowing (TOS) and in both years (Table 1). TOS 1 and 2 produced similar plant densities for the same seeding rates. Plant densities in TOS 3 were lower than both TOS 2 and TOS 3, though only significant at the 175 kg/ha rate.

Table 1. Average 1998 and 1999 plant densities/m2 for 7 seeding rates and 3 times of sowing.

 

25 kg/ha

50 kg/ha

75 kg/ha

100 kg/ha

125 kg/ha

150 kg/ha

175 kg/ha

TOS 1

19.4

28.0

40.0

53.0

59.4

65.1

79.8

TOS 2

21.8

28.0

36.4

51.9

69.8

74.5

81.9

TOS 3

14.3

26.6

32.6

47.4

55.0

61.3

67.0

L.S.D. (P<0.05). TOS 8.9, Rate 5.4, TOS x Rate 12.1

Lupin dry matter production at anthesis increased with seeding rates (Figure1). Dry matter continued to increase up to the 175 kg/ha rate (67 plants/m2) in TOS 3 and 150 kg/ha rate (74.5 plants/m2) in TOS 2. There was no significant increase in dry matter above the 100 kg/ha rate (53 plants/m2) in TOS 1. When combined across all TOS, an extra 1.0 t/ha of dry matter was produced as densities were increased from 30 plants/m2 to 60 plants/m2.

Evans et al. (3) demonstrated that the amount of nitrogen fixed by a lupin crop is directly proportional to the bulk of growth produced. High lupin plant densities in these experiments are therefore likely to have increased nitrogen fixation and resulted in greater soil protection due to more rapid ground cover and increased trash post-harvest. Weeds are also often less of a problem in a dense lupin stand (5).

Lupin grain yield increased in a similar trend to dry matter production as seeding rate increased. Grain yield increased up to the 150 kg/ha rate (65 plants/m2) in TOS 1 and fell marginally at the highest rate. Grain yield continued to increase up to the highest seeding rate in both TOS 2 (81.9 plants/m2) and TOS 3 (67 plants/m2). On average an extra 0.4 t/ha of grain yield was produced when densities were increased from 30 plants/m2 to 60 plants/m2.

Figure 1. Average 1998 and 1999 lupin dry matter production at anthesis (a) and grain yield (b) for 7 seeding rates and 3 times of sowing. Vertical bar is L.S.D (P< 0.05) analysed for seeding rates within TOS 1, 2 and 3.

CONCLUSION

Higher seeding rates than used in the past are needed to maximise lupin yield and dry matter production in the Victorian Mallee, confirming previous work conducted in Western Australia (2). Seeding rate becomes even more important when sowing is delayed beyond the end of April. Rates of 125 kg/ha of good quality seed are required to achieve the desired 60 plants/m2 with current varieties. Plant densities of up to 75 plants/m2 appear to have no detrimental effect on yield or dry matter production.

ACKNOWLEDGMENTS

The authors thank the Mallee Research Station’s operations group staff, Craig Bell and David Grayling for assistance with field operations and Jo Latta for scientific input and advice.

References

1. Boundy, K.A. 1980. Proceedings. Grain Legume Workshop. Longerenong, p 21-27.

2. Cowling, W.A. and Speijers, E.J. 1994. Proceedings. 1st Australian Lupin Technical Symposium. Perth, p 262.

3. Evans, J., O’Connor, G., Turner, G., Bergersen, F., Coventry, D., Armstrong, E. and Seymour, A. 1986. Proceedings. 4th International Lupin Conference. Geraldton, p 308.

4. Mock, I.T. and Corbett, A.J. 1997. Proceedings. Farming Systems Developments Workshop. Adelaide, p 67-68.

5. Walton, G.H. 1982. Journal of Agriculture. Dept Agriculture, Western Australia 3, 77-80.

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