All plants require nitrogen for growth and although this is freely available in the atmosphere, it is not in a form that plants can utilise.
Legume plants have the unique ability to fix atmospheric nitrogen by means of bacteria which live in symbiosis on the nodules of their roots.
There are numerous species of these bacteria and each has the ability to nodulate different host plants. These bacteria have been isolated and separate cultures prepared in a peat medium which can be used to distribute the bacteria over the surface of the seed prior to sowing. This distribution over the seed will ensure effective nodulation and thus the process of nitrogen fixation by the host plant.
The use of these peat cultures is always advisable when the legume crop or plant is introduced to new land for the first time. In virgin soils, the response to inoculant is not spectacular since soils rarely contain the appropriate Rhizobia. There is evidence that inoculant hastens establishment of the pasture and in most cases more nodules are formed on neutral rather than on acid soils.
In some cases, the soils may already contain adequate numbers of effective bacteria from previous sowings of similar legumes. The conditions may also be adverse for bacteria and the host plant, for example, acid soils, waterlogged conditions, soil too dry or from various deficiencies.
It should therefore be recognised that with so many variables, the use of commercial cultures will help to ensure effective nodulation and that the correct strain of Rhizobium is available in the soil for the host plant. in the early 1930's, little more than the maintenance of a small range of mostly imported strains of Rhizobium was attempted. With the advent of the tropical pasture revolution there was a need to accumulate knowledge and to rethink the philosophy and development of the legume Rhizobium symbiosis. Today there exists very specific strains of bacteria, particularly among the tropical species.
It should be recognised that mixing of inoculated seed with superphosphate for even one hour before sowing will significantly reduce establishment and prolonged contact will completely eliminate the bacteria. Exposure of the inoculated seed to sunlight, high temperatures, dry conditions and chemicals will also be detrimental to the bacteria and special precautions need to be taken.
Methods of Peat Inoculation
There are many procedures for inoculating seed available and the method chosen depends on a number of factors, such as the expected response to inoculation, the trouble the farmer is prepared to go to, the acidity of the soil and the contact between the seed and the fertiliser etc.
These methods include...
Slurry Inoculation: Prepare a slurry by mixing the contents of the packet with 1000mls (1 litre) of cool, clean water. Pour this slurry mixture over the correct weight of the seed and mix thoroughly making sure that all the seeds are evenly coated.
Dusting: The peat culture is mixed with the seed and may be carried out in the drill or combine. The seed may be pre-moistened with water.
Lime pelleting: An adhesive material is used and there are many grades of Methyl Cellulose on the market, some of which are required to be dissolved in boiling water and other in cold water.
Methods of Peat Inoculant Application
A) Calculate the quantities of materials needed for different legumes. The quantities required will vary with the size of the seed.
B) Mix the peat culture with pre-prepared adhesive making sure the solution has been cooled first.
C) Pour this mixture over the seed and stir until all the seeds are wet.
D) Add immediately the required amount of finely ground limestone and mix until the seeds are evenly coated and well pelleted. Cease mixing as soon as the pellet has been formed.
The adhesive used in pelleting provides some protection for the bacteria from the harmful effects of high temperatures and the drying associated with storage and dry sowing. However, it is best to inoculate seed as close as possible to sowing. Ideally, it should be sown into moist soil immediately.
Methods of Freeze Dried Inoculant Application
Directions for preparation of legume inoculant solution:
EasyRhiz (R) is supplied in two parts which are combined before use:
1. A glass vial of freeze dried Rhizobium bacteria for inoculating legume seed.
2. A pack of EasyRhiz (R) protecting agent.
This product is suitable for both coating seed prior to sowing and liquid injection during sowing. The maximum amount of seed that can be treated is indicated on the vial label. Use one pack of EasyRhiz Protecting Agent per vial.
Inoculant solution preparation
Remove cap and rubber bung from the glass vial, add clean cool water, replace bung and shake to dissolve powder. All powder must dissolve. It is preferable to use rain water with a pH between 6.5 and 7.5.
For Seed Coating:
1. Add this pack of powder to sufficient water to treat the weight of the seed indicated on the vial. As a guide, 50kgs of small seed requires 750mls water, 250kgs medium size seed requires 1.5 litres water and 500kgs large seed requires 3 litres water. Adjust water rates as required. Using less water will shorten drying time but may reduce seed coverage.
2. Mix in the vial of Inoculant solution prepared earlier. Rinse the vial.
3. Coat this solution evenly over the seed to be treated.
Treated seed should be planted within 5 hours of inoculation.
For Liquid Injection:
1. Add 2 litres of cool clean water to a clean bucket, add EazyRhiz (R) Protecting Agent , then add the vial of inoculant solution prepared earlier. Rinse the vial.
2. Add this solution to the spray tank of a liquid injection system on a crop seeder or combine, at 50 to 200 litres of clean water per hectare. The liquid injection system delivers the solution into the planting furrow along with the seed during the planting process. It is important that the inoculant solution contacts the seed as it is sown.
Store the vial between 4 degrees celcius and 10 degrees celcius out of direct sunlight. Apply only to the specific legume seed indicated o the label of the vial.
Do not prepare inoculant in containers that have previously contained pesticides.
Do not use if sowing into soil with poor soil moisture (dry sowing).
Do not use if sowing into soil that is over 30 degrees celcius. Do not apply to seed that is coated with toxic chemicals.
Note: Increased application rates improve results. Double the concentration of inoculant (i.e. use 2 vials instead of 1) if the land has never grown this type of legume crop previously (keep the application of water standard).
As the manner of use of this product is beyond the company's control, no warranty is given other than those warranties implied by the Trade Practices Act 1974 and in any event the liability of the company is limited to replacement of this product or the payment of the cost of doing so.
EasyRhis (TM) is a soluble powder of pure culture supplied in a glass vial and comes with EasyRhiz (TM) protecting agent.
All Rhizobium strains used are approved by the NSW Department of Primary Industries, 2009.
Store all cultures in a cool place.
Freeze Dried Inoculant information supplied by New-Edge Microbials Pty Ltd