Finding the best irrigated pasture legume
PRODUCTION ADVICE - JULY 2020 - AGRONOMY
By John Fowler
Extension Agronomist
P: 03 5881 9933 | M: 0427 079 138 | E: john.fowler@lls.nsw.gov.au
Is sub clover still the best annual legume for irrigated pasture production in the Murray region? This is one of the questions a four-year project being funded by the Australian Government National Landcare Program hopes to answer. The project is being conducted across the Murray Irrigation Limited footprint by Murray Local Land Services.
Last year, four replicated variety trials were assessed, looking at a total of 22 pasture legume varieties. The results for one of the trials at Berrigan are summarised in the following table:
Variety | Autumn Yield | Spring Yield | Total Yield | Relative |
Maral Persian clover | 2,467 | 2,478 | 4,945 | 71% |
Prima Gland clover | 2,233 | 1,138 | 3,371 | 48% |
Laser Persian Clover | 2,153 | 3,738 | 5,891 | 84% |
Sava snail medic | 1,808 | 0 | 1,808 | 26% |
Antas sub Clover | 1,601 | 5,304 | 6,905 | 99% |
Seelu arrowleaf clover | 1,584 | 5,398 | 6,982 | 100% |
Yellotas serradella | 1,364 | 4,054 | 5,418 | 78% |
Haifa white clover | 1,306 | 2,838 | 4,144 | 59% |
Casbah biserrula | 1,227 | 5,554 | 6,781 | 97% |
Yanco sub clover | 1,016 | 2,962 | 3,978 | 57% |
Trikkala sub clover | 886 | 3,640 | 4,526 | 65% |
Longhaul balansa clover | 813 | 4,012 | 4,825 | 69% |
Berseem clover | 686 | 2,808 | 3,494 | 50% |
Electra purple clover | 0 | 4,126 | 4,126 | 59% |
Titan 7 lucerne | 0 | 1,626 | 1,626 | 23% |
Some of the ‘lessons learnt’ from the first year are:
Importance of weed-free seed beds
Two of the four trial sites were greatly impacted by broadleaf weeds. It became obvious that to successfully establish pasture legumes, the site needs to be free of broadleaf weeds, especially vigorous weeds such as capeweed and Paterson’s curse.
One site was pre-irrigated to allow weeds to germinate, then cultivated prior to sowing. While this practice reduced the weed pressure, it did not eliminate it. Not all the capeweed germinated with the pre-irrigation, and a large population germinated when the trial was irrigated a month later.
The only way to be sure that broadleaf weeds are not present is to monitor the site for at least two years prior to sowing.
Grazing management for most clovers is different to that of sub clover
Sub clover has been the traditional legume grown in irrigated annual pastures in the Murray region. It differs from most of the other trial species as it buries its seed rather than set it aerially (i.e. at the top of the plant canopy). If the grazing management commonly used on sub clover is used on newly sown aerially seeding varieties, then seed survival can be substantially reduced, leading to poor re-establishment the following season.
This problem was highlighted in a preliminary trial sown in 2018. The legumes in the trial grew well the first year and set substantial quantities of seed. However, the site was then grazed heavily once the legumes had senesced. During this grazing, most of the seed was eaten by the sheep, and these varieties failed to re-establish the following season.
Pasture legume species have similar feed quality
Feed quality testing showed that most pasture legumes growing at the same site have similar feed value. It appears that feed value is more impacted by growing conditions than by variety.
Snail medic, for instance, had a metabolisable energy (ME) of 12.3 MJ/kg when grown on a loam soil at Berrigan, but only 11.5 MJ/kg when grown on a heavy grey clay at Noorong. By comparison, nearly all the legumes in the Berrigan trial had ME values of between 12.1 and 12.4 MJ/kg (the exceptions being Maral Persian clover with an ME of 12.7 MJ/kg and Yellotas serradella with an ME of 11.9 MJ/kg).
This is shown in the following table, which summarises autumn feed quality at the Berrigan trial site plus the snail medic at the Noorong site.
Variety | Metabolisable Energy (MJ/kg) | Dry Matter Digestibility | Crude Protein | Neutral Detergent Fibre |
Maral Persian clover | 12.7 | 83% | 25.8% | 31% |
Laser Persian clover | 12.3 | 81% | 23.8% | 32% |
Prima gland clover | 12.4 | 82% | 29.1% | 32% |
Seelu arrowleaf clover | 12.3 | 81% | 25.7% | 32% |
Antas sub clover | 12.1 | 80% | 25.2% | 35% |
Haifa white clover | 12.4 | 82% | 27.2% | 32% |
Yellotas serradella | 11.9 | 79% | 27.5% | 35% |
Casbah biserrula | 12.1 | 80% | 27.9% | 32% |
Sava snail medic | 12.3 | 81% | 25.3% | 35% |
Sava snail medic (Noorong) | 11.5 | 76% | 24.1% | 35% |
Pasture legume species have different growth patterns
There was a substantial variation in early autumn growth between pasture legume species. Several species are not able to meet the autumn feed gap demand on mixed enterprise irrigation properties. However, some of these species (e.g. purple clover) may be suitable to grow for fodder conservation (e.g. hay) in the spring.
Autumn production from species such as biserrula and purple clover is quite low, but their spring production is relatively high. Conversely, autumn production from gland clover and snail medic is relatively high, but their spring production is quite low (see the production data in the first table).
The importance of a timely spring irrigation in the first year
Three of the trials received timely spring irrigations that aided seed set in the first year. This resulted in good re-establishment of most varieties in the autumn of the second year.
The fourth site was irrigated in the spring, but too late to impact seed set. Consequently, establishment was quite poor in autumn 2020. The average re-establishment of legume species at this site was about 75 per cent lower than at the other three sites.
Establishment of four varieties at each site is shown in the following table (Note: not all varieties were at every site).
| Autumn 2020 Establishment (plants/m2) | |||
Variety | Site #1 | Site #2 | Site #3 | Site #4 |
Antas sub clover | 1,420 | 1,086 | 1,633 | 513 |
Trikkala sub clover | 1,920 | 1,720 | 1,433 | 253 |
Longhaul balansa clover | 1,160 | - | 1,060 | 406 |
Prima gland clover | 1,646 | 2,940 | - | 40 |
Conclusion
The project needs to run for more years before any firm conclusions can be made. It may be that there is no single ‘best’ pasture legume species, but it may depend on what the main requirement of the pasture is – i.e. is it to maximise autumn growth, spring growth or just to persist through dry years?
This project is supported by Murray Local Land Services through funding from the Australian Government’s National Landcare Program.