Annual legumes - Ilford demo site report

AG ADVICE - March 2021

Clare Edwards - Senior Land Services Officer, Pastures

In 2020, we ran a demonstration plot trialling hard seeded legumes in the Ilford area. Part of the trial was to have a 'look and see' at some new cool season annual legumes alongside some traditional varieties.

There are many interesting aspects when looking at some of these legumes, including whether they have any distinct advantages when considering climate variability.

The site was a paddock that had previously been sown to oats for a couple of years. Then in 2019, the trial that was originally sown failed due to the drought. The site had been limed previously, and in 2020 had a pHCa of 5.3 in the top 10cm. In February 2020, the site was again sown to 7 different annual legumes and two perennials (white clover and lucerne). The annuals included balansa, arrowleaf, gland, yellow serradella, pink serradella and two different hardseeded levels of sub-clover.

One of the factors to consider when selecting the species sown was their hard seeded levels. This is a seed dormancy mechanism, which is an important trait that allows the plant to create a long-term seed bank. It can regulate the germination of the plant and so protect against false breaks. As an annual, this is important; some years we have good soil moisture and cool conditions early on, only to receive a couple of hot, dry weeks at the end of summer or in early autumn. Newly germinated plants find it hard to survive in these conditions.

Hard seededness also prevents every single seed germinating at the same time. This can lead to crowding and competition for nutrients, space, light and moisture. Lastly, the hard seeded trait increases the future survival of the species. Often only a percentage of seed germinates in any one year, and there is seed still remaining in the soil.

A lot of landholders commented on the amount of sub clover in their pasture last year (2020), even though there had been little sub clover visible in the proceeding few years, and they had not sown any seed for several years.

Many annuals have a percentage of hard seededness. There can also be differences between varieties - for example the sub-clover varieties of Woogenellup can have lower level of hard seededness when compared to Seaton Park LF variety. It is often commented that landholders see a disappointing second year of hard seeded legumes, partly due to pasture management in the establishment year.

The two perennial legumes were added into the demonstration to help answer the question on the use of perennials in a region that receives some summer rainfall. Legumes are not only important to help fix nitrogen for our pastures, but also add to the quality of feed they can produce for our livestock.

While we were not able to hold major events at the site last year, a small group were able to visit and hear about the different types of legumes. Forage samples were also taken and discussed on the day. Below is a table of the legume samples sent away for feed quality analysis. Note that these were taken at one point in time (May), and are not replicated. Vetch had previously been sown as part of the oat crop and was a volunteer legume. There was insufficient pink serradella and lucerne at the time to take a representative sample.

Table 1. Feed quality of 8 legumes at the Ilford site, May 2020. Samples taken by grab method and randomised across the plots. Samples sent to NSW Department of Primary Industries Wagga Wagga Feed Quality Service.