Farmers love a new pasture variety, and the new kid on the block is Trigonella balansae, Carn2ac – a legume variety that has been selected and cultivated to suit the difficult West Australian Wheatbelt soils.
It is related to fenugreek and has been selected due its early flowering and non-shattering seed pod. It flowers in about 78 days and is aerial seeding, allowing farmers to harvest their own seeds.
South West NRM spoke to Professor John Howieson from Murdoch University to get more details on the new cultivar and why it will improve pastures in WA.
What soils does Trigonella grow best in?
Trigonella goes best in fine textured clay and clay loams, usually alkaline in pH (6-9) and hard setting. Most pasture legumes are highly specific in the soils they are suited to. We have a huge mosaic of soil types in WA which is why we need a large variety of crop species to grow on them.
(If you’ve got more acidic soils, you might find our previous article on serradella of interest.)
Does seed persist in the soil bank?
The Trigonella has very hard seed, too, so it will persist in soil when used in rotation with crops. The benefit of this is you only have to sow the pasture once for it to form a seed bank, then you can crop it several times to use the nitrogen and then the plant regenerates from the seed bank in the soil. It fixes a lot of nitrogen because it grows so well, and that nitrogen transfers into the following cereal or canola crop.
Does it fix sufficient nitrogen for the following crop or do farmers still need to add nitrogen fertiliser?
Our experiments show the next crop doesn’t need any nitrogen, and you can get the same yields and the same protein, although most farmers are reluctant to completely leave nitrogen out. It does depend on how much nitrogen mineralises from the legume, and that depends on how warm the autumn is, how much summer rain falls and how warm the winter is. We are confident that from a well-grown Trigonella crop you can get a good cereal crop without the need to put fertiliser nitrogen on. The nitrogen applied to cropping systems is the cause of half of that industry’s carbon footprint. Take that out and you’ve got a much more sustainable cropping system. The energy required to make urea is incredibly high and the majority is imported.
Is there a crossover in the suitability between Lebeckia, Serradella and Trigonella?
No. The Lebeckia and Serradella love the sandy soils and generally those sandy soils are acidic. We’ve released many cultivars of Serradella for the sandy soils, but there couldn’t be anything less suited for the sandy soils than Trigonella. In the same way, Serradella is totally unsuited for fine textured soils. They each fill a different niche.
What species does Trigonella grow well with for multispecies pastures?
Trigonella grows well with medics. If you want to put in a multispecies pasture you would put in Diaman2ti, Carn2ac and you could put in an annual medic if you can get the seed for it. Diaman2ti bladder clover goes well on more neutral pH soils.
Is the seed likely to be easier and cheaper to source than other legume varieties?
With medics and sub-clover you’ve got to suction harvest the pods, and that means you wait until the end of the growing season, tickle up the soil, suck it up with a sort of vacuum and then it requires substantial further processing. All those things add a few dollars per kg to the price of seed. With the Trigonella, you can harvest it with a cereal header, you don’t even have to change the settings. Same with the Diaman2ti, all the new pastures we have developed have been selected so that farmers can produce their own seed.
Seed is available to be purchased from Clint Butler in Narembeen. Phone 0429 647 335.
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