Lebeckia: a perennial for deep sandy soils

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1. Summary

Agriculture highly depends on fertilisation to improve crop yield. An alternative to industrial fertilisers, which require fossil fuels for production, is the use of legume plants related to our garden beans, that are able to fix Nitrogen from the air, with the help of soil bacteria. The south-west of Western Australia is a major farming area in which annual rainfall has declined by more than 20% in the last 30 years. Most farming systems in these areas use annual legumes for nitrogen fixation, but these plants are water demanding. With the perspective of increasing effects of climate change and more unpredictable rainfall they are becoming unreliable.

The deep rooted, herbaceous shrub Lebeckia ambigua, which we discovered in the Western Cape of South Africa, does not only grow on poor, acidic, sandy soils with annual rainfall of 150-400mm, but it also produces high quality forage in those conditions.

Because of these qualities, we believe that it is a prime candidate that will help us to support farmers turning the poorest soils into green farmable landscapes. I believe the three great things arise from our system: No artificial fertiliser, more fodder for grazing with less water and less impact on the environment.

2. Description

Our current research is focusing on Lebeckia plant breeding, inoculant formulation and seed production.

Lebeckia ambigua is still a ‘wild’ plant, which means that the plants of one population do not all flower simultaneously. Therefore they do not have the same height or produce seed at the same time. This type of variability is very inconvenient if you intend to use Lebeckia as an agricultural crop. To improve these undesirable traits we have started an intense breeding program to produce commercial cultivars that offer ideal performance in acidic deep sandy soils, often found in agricultural regions across Australia.

As most legumes, Lebeckia forms a symbiosis with soil bacteria to obtain nitrogen, a vital nutrient for all plants. Detailed investigation of these beneficial symbionts has identified them as novel bacterial species. In order to achieve maximal nitrogen fixation capacity of the plant, the bacteria need to be present when the plant germinates. This is easily achieved, by sowing seeds and bacterial material simultaneously, also called inoculation of the seed. Part of our research is thus focusing to obtain the best possible inoculant for Lebeckia. Besides viable bacterial cells, such an inoculum also has a non-active carrier component that together should produce a product with high efficacy and a long stable shelf life. Therefore, it is important to find the best possible combination of a robust bacterial strain and an ideal yet cost effective carrier. Without a suitable carrier, the bacterial population declines rapidly when inoculated into soil or with seeds and fails to build a sufficient stable reservoir in the rhizosphere to achieve maximum nitrogen fixation. We are investigating several carrier types including peat, peat granules, encapsulation, perlite or vermiculite and have also started to test the use of additives or protectants such as Glycerol, Sucrose, CMC (carboxyl methyl cellulose), Gum Arabic, Charcoal and PVP (polyvinyl-pyrrolidone)), either as a single component or in combination depending on the type of inoculum application (seed or soil). Our research will result in an optimised Lebeckia inoculant that will stimulate maximal nitrogen fixation in the plant.

As we aim to deliver a complete product to the farmers, including the optimized inoculum and seeds, we will start with seed increase trials once an optimal cultivar has been obtained to ensure stable seed supply to the farmers. In this way we ensure quality and availability of the complete package for our farmers.

3. Additional Details

More inofmration on the different research topics of our group can be found on our website: http://www.murdoch.edu.au/Research-capabilities/Centre-for-Rhizobium-Studies/

If you like to follow us more closely, visit our Facebook page: https://www.facebook.com/CentreforRhizobiumStudies?ref=aymt_homepage_panel

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My career in the field of rhizobiology research started during my master’s thesis, which investigated Burkholderia bacteria in root nodules from Belgian legumes. As the project revealed interesting...