Molybdenum, row spacing, plant population and PGRs in Faba beans

By Damian Jones, ICC

Key messages:

ICC_Trial_Summary_Book_ cover

  • Applying molybdenum to faba beans did not effect nodulation or plant moly levels.
  • Faba beans sown at 25 plants/m² on 7½ inch row spacings produced the highest yields.
  • PGRs had no effect on the yield, height or lodging of faba beans.
  • Faba beans sown with a precision planter may benefit crop performance.

Molybdenum Application

Molybdenum is required by plants as part of the process of converting soil nitrate to amino acids, as well as by the rhizobia in root nodules in legumes that fix atmospheric nitrogen (N²).

Traditionally clover pastures were fertilised with moly super, but the practice seems to be rare these days. So with the rise in the popularity of faba beans, is there sufficient soil molybdenum to ensure nitrogen fixation is not limited?

Molybdenum can be applied to crops as Molytrac (thanks to assistance from Yara) either as a seed dressing (3L/t) or as a foliar spray (500ml/ha).

Tissue tests taken in August had shown an increase in plant moly levels, but the control (no moly applied) had adequate levels (> 0.5 mg/kg).

Examination of the roots of the plants showed no appreciable difference in nodulation between the treatments or colour differences inside the nodules (a functioning nodule is pink/red inside whereas a non-functioning nodule is green/pale).

Harvest results confirmed that the moly levels in the control were adequate, with yields similar across the three treatments.

Table 1: Results of molybdenum on faba bean trial.
Treatment

Yield (t/ha)

Tissue Test
Molybdenum (mg/ kg)

Control

6.24

0.67

Foliar Moly

5.89

1.30

Seed + Moly

5.85

1.40

P

LSD

CV%

0.693

Adequate Moly >0.5 mg/kg

NS

9.8

Row spacing and plant populations

The current BMP for faba beans is to target a plant population of 25 plants/m². There was some discussion early in the season that the lodging seen in 2014 may have been due to too high a population.

To test this theory, a trial was sown with plant populations of 15 and 25 plants/m² and on 7½ and 15 inch row spacings.

Table 2. Faba bean yields when sown at 7.5″ and 15″ row spacings.

Row spacing yields

Spacing (inch)

Yield (t/ha)

7½”

6.44

15”

6.09

P

0.003

LSD

0.224

CV%

5.3

Table 3. Faba bean yields at 15 pl/m² and 25 pl/m².

Plant population yields

Plants/m²

Yield (t/ha)

15

6.15

25

6.40

P

0.038

LSD

0.240

CV%

5.6

From the trial results, a target population of 25 plants/m² at a row spacing of 7½ inches gave the highest yields.

Plant Growth Regulators

The aim of this trial was to find a PGR that works.

Having a PGR would be useful in some situations such as to help control the height of the crop in an effort to reduce lodging. For example, ICC’s variety trial in 2010 was approximately two metres tall and collapsed close to harvest into a tangled mess.

Note: There are no PGRs registered for use on faba beans.

The PGR Reward (mepiquat) and the triazole fungicide Prosaro were applied to the faba beans on August 14, prior to flowering.

Table 4. Yield, height and lodging of faba beans applied with PGR.
PGR

Yield (t/ha)

Height (cm)

Lodge Score

Control

6.24

137

4.3

Reward

6.24

133

4.3

Prosaro

6.34

127

3.7

P

0.795

0.373

0.694

LSD

NS

NS

NS

CV%

3.3

6.2

20

The PGRs had no effect on yield, height or lodging.

Timing of application needs to be investigated as the relatively late applications do not seem to be having an effect, but applying too early may reduce the height of the first pod and increase harvest losses.

Precision planting

A trial looking at the performance of faba beans sown by a precision planter was established after a grower noted that a crop that was precision planted and looked to be a far better crop than a combine sown crop.

As ICC doesn’t have access to a precision planter, the plots were sown by hand.

Establishment was faster and more even than the plots sown by our seeder. However looks aren’t everything and the promising start failed to materialise into yield.

Planting

Yield (t/ha)

Control

6.034

Precision Planted

6.336

P

0.106

LSD

NS

CV%

4.6

GRDCLogoStacked_TM_CMYKThe stubble project – maintaining profitable farming systems in Victoria and Tasmania with retained stubble (project number BWD00024) is funded by the GRDC.

A printer-friendly version of this trial report can be accessed here.

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About BCG

Birchip Cropping Group Inc. (BCG) is a not-for-profit agricultural research and extension organisation led by farmers in the Victorian Wimmera and Mallee.
This entry was posted in Break crops in retained stubble systems, Disease management, Research results, Row spacing, Seeding systems and tagged , , , , , , . Bookmark the permalink.

3 Responses to Molybdenum, row spacing, plant population and PGRs in Faba beans

  1. Pingback: 2015 field trials | The stubble project: Victoria and Tasmania

  2. Pingback: Row spacing and stubble retention on irrigation | The stubble project: Victoria and Tasmania

  3. Pingback: Break crops in stubble retained systems under irrigation | The stubble project: Victoria and Tasmania

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