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A comparison of three inoculation treatments on lupins

I. T. Mock

Mallee Research Station, Walpeup, Vic.,3507

The application of Serradella-type G inoculum to lupin seed before sowing increases nodulation and grain yield (1). An experiment was conducted to determine the effects of applying inoculum by means of a soil spray at sowing compared to the usual practice of inoculating seed 2-72 hours before sowing.

Methods

Unicrop lupins were sown at 100 kg/ha on an alkaline sand with 15 kgP/ha. The treatments applied were: (a) no inoculation; (b) pre-sowing seed inoculation - 100 g Seradella-type G/100 kg seed applied as a slurry three hours before sowing; (c) soil inoculation - 150 g inoculum applied with 150 e/ha water and sprayed into the drill row from a nozzle mounted behind the sowing boot.

Results and Discussion

Both inoculation treatments resulted in more plants with nodules and increased dry matter (DM) yield per plant (tops and roots) at both harvests (Table 1). The plants from uninoculated seed were chlorotic, less branched and smaller than those from inoculated seed.

Table 1: Effects of inoculation on nodule production and plant DM yield

Inoculation
treatment

63 days after sowing

94 days after sowing

Nodulation
(% of plants)

Plant DM (g)

Nodulation
(% of plants)

Plant DM (g)

Nil
Pre-sowing
Soil-applied

20.0 a
90.9 b
82.1 b

0.36 a
0.41 a
0.42 a

67.0 a
99.5 b
98.5 b

1.30 a
2.12 b
2.01 b

Values followed by the same letter in each column do not differ significantly (P<0.01).

Table 2: Location of nodules on nodulated plants (2 of nodulated plants)

 

63 days after sowing

94 days after sowing

Treatment

Tap root
only
(2)

Lateral
root only
(%)

Tap and
lateral

rooUCts

Tap Ta root
only
(%)

Lateral
root only
(%)

Tap and
lateral
ro(2)ots

Nil

65.8

24.4

9.8

7.1

66.6

26.4

Pre-sowing

42.9

12.1

45.0

10.2

19.3

70.5

Soil-applied

40.9

15.1

54.0

4.0

22.0

74.0

Most of the nodulated plants in uninoculated plots had nodules on the tap root only at 63 days after sowing (Table 2). However, 31 days later, nodule development was predominantly on lateral roots. In the inoculated plots, 63 days after sowing, plants either had nodules on the tap root only or on both the tap and lateral roots. Later nodule development was apparently on the lateral roots of plants already supporting nodules on the tap root.

There were no significant differences between the two inoculation treatments. Application of inoculum at sowing reduces grain handling and there are no problems of diminishing viability if sowing is delayed.

1. Ridge, P. E. (1980). Proc. Grain Legume Workshop, Longerenong Agricultural College, pp.2-10.

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