Cropping regions in south-west Victoria have had a significant increase in the amount of legume crops grown.
Legumes are becoming a popular crop in the rotation.
Not only can they receive favourable grain prices at harvest compared to cereals, but the plants themselves can fixate large amounts of nitrogen back into the soil during the season, benefitting the next crop in that paddock’s rotation.
The ability to fix nitrogen and earn an income from the crop is attractive to many growers. However, there’s a lot to be learnt about the rhizobia that help in fixing that nitrogen, and the inoculation techniques that can be used to provide appropriate amounts and types of rhizobia. Inoculants for legumes are products containing commercially prepared cultures of rhizobia in formulations such as peat slurry or granules that supply large numbers of viable rhizobia for effective nodulation.
Peat slurry has been and still is a popular method of inoculating legumes, but the arrival of new granular forms of peat inoculant have been appealing due to their ability to be dry sown, and because they do not have to be sown within a 24 hour timeframe as peat inoculant does.
There have been concerns about granular inoculant not providing as strong results as peat slurry, although this perhaps is not so much a question of the viability of granular inoculant.
When using granular inoculant, it is important to ensure that it is placed in its own seed box on the seeder so that it is fed out consistently with the legume seed. If inoculant is placed on top of the legume seed in the seed bin, the inoculant can fall to the bottom of the bin, meaning that only some seed in the bin is sown with inoculant. This can create issues with establishment and vigour during the season in those plants that missed out on inoculant.
Nodulation in the area of the paddock that did not receive inoculant will also be compromised. Less nitrogen will be fixed in these areas, creating uneven soil fertility within the paddock for ensuing crops.
