Is there sufficient Ensifer and Rhizobium species diversity in UK farmland soils to support red clover (Trifolium pratense), white clover (T. repens), lucerne (Medicago sativa) and black medic (M. lupulina)?

Rhizobia play important roles in agriculture owing to their ability to fix nitrogen through a symbiosis with legumes. The specificity of rhizobia-legume associations means that underused legume species may depend on seed inoculation with their rhizobial partners. For black medic (Medicago lupulina) and lucerne (Medicago sativa) little is known about the natural prevalence of their rhizobial partner Ensifer meliloti in UK soils, so that the need for inoculating them is unclear. We analysed the site-dependence of rhizobial seed inoculation effects on the subsequent ability of rhizobial communities to form symbioses with four legume species (Medicago lupulina, M. sativa, Trifolium repens and T. pratense). At ten organic farms across the UK, a species-diverse legume based mixture (LBM) which included these four species was grown. The LBM seed was inoculated with a mix of commercial inocula specific for clover and lucerne. At each site, soil from the LBM treatment was compared to the soil sampled prior to the sowing of the LBM (the control). From each site and each of the two treatments, a suspension of soils was applied to seedlings of the four legume species and grown in axenic conditions for six weeks. Root nodules were counted and their rhizobia isolated. PCR and sequencing of a fragment of the gyrB gene from rhizobial isolates allowed identification of strains. The number of nodules on each of the four legume species was significantly increased when inoculated with soil from the LBM treatment compared to the control. Both the proportion of plants forming nodules and the number of nodules formed varied significantly by site, with sites significantly affecting the Medicago species but not the Trifolium species. These differences in nodulation were broadly reflected in plant biomass where site and treatment interacted; at some sites there was a significant advantage from inoculation with the commercial inoculum but not at others. In particular, this study has demonstrated the commercial merit of inoculation of lucerne with compatible rhizobia

Net nitrogen balances for cool-season grain legume crops and contributions to wheat nitrogen uptake: a review

Copyright © 2001 CSIROThe removal of nitrogen (N) in grain cereal and canola crops in Australia exceeds 0.3 million t N/year and is increasing with improvements in average crop yields. Although N fertiliser applications to cereals are also rising, N2-fixing legumes still play a pivotal role through inputs of biologically fixed N in crop and pasture systems. This review collates Australian data on the effects of grain legume N2 fixation, the net N balance of legume cropping, summarises trends in the soil N balance in grain legume–cereal rotations, and evaluates the direct contribution of grain legume stubble and root N to wheat production in southern Australia. The net effect of grain legume N2 fixation on the soil N balance, i.e. the difference between fixed N and N harvested in legume grain (Nadd) ranges widely, viz. lupin –29–247 kg N/ha (mean 80), pea –46–181 kg N/ha (mean 40), chickpea –67–102 kg N/ha (mean 6), and faba bean 8–271 kg N/ha (mean 113). Nadd is found to be related to the amount (Nfix) and proportion (Pfix) of crop N derived from N2 fixation, but not to legume grain yield (GY). When Nfix exceeded 30 (lupin), 39 (pea) and 49 (chickpea) kg N/ha the N balance was frequently positive, averaging 0.60 kg N/kg of N fixed. Since Nfix increased with shoot dry matter (SDM) (21 kg N fixed/t SDM; pea and lupin) and Pfix (pea, lupin and chickpea), increases in SDM and Pfix usually increased the legume’s effect on soil N balance. Additive effects of SDM, Pfix and GY explained most (R2 = 0.87) of the variation in Nadd. Using crop-specific models based on these parameters the average effects of grain legumes on soil N balance across Australia were estimated to be 88 (lupin), 44 (pea) and 18 (chickpea) kg N/ha. Values of Nadd for the combined legumes were 47 kg N/ha in south-eastern Australia and 90 kg N/ha in south-western Australia. The average net N input from lupin crops was estimated to increase from 61 to 79 kg N/ha as annual rainfall rose from 445 to 627 mm across 3 shires in the south-east. The comparative average input from pea was 37 to 47 kg N/ha with least input in the higher rainfall shires. When the effects of legumes on soil N balance in south-eastern Australia were compared with average amounts of N removed in wheat grain, pea–wheat (1:1) sequences were considered less sustainable for N than lupin–wheat (1:1) sequences, while in south-western Australia the latter were considered sustainable. Nitrogen mineralised from lupin residues was estimated to contribute 40% of the N in the average grain yield of a following wheat crop, and that from pea residues, 15–30%; respectively, about 25 and 15 kg N/ha. Therefore, it was concluded that the majority of wheat N must be obtained from pre-existing soil sources. As the amounts above represented only 25–35% of the total N added to soil by grain legumes, the residual amount of N in legume residues is likely to be important in sustaining those pre-existing soil sources of N.J. Evans, A. M. McNeill, M. J. Unkovich, N. A. Fettell and D. P. Heena

Phosphorus-use efficiency, growth and yield of spelt wheat ('Triticum aestivum ssp. spelta') compared with standard wheat ('T. aestivum ssp. vulgare') in south-eastern Australia

Experiments were conducted in the glasshouse and the field to assess the phosphorus-use efficiency, yield, and yield components of several spelt wheat genotypes in comparison with standard bread wheats. Spelt genotypes had much lower grain yield than standard bread wheats, in both a wellwatered glasshouse and three field situations. The reduction in yield was often as great as 60% and was largest in late-flowering spelt genotypes. Spelt genotypes responded to increasing amounts of applied phosphorus (P) fertiliser, adequately acquired P from soil, and some had higher total amounts in their tissues; however, these P reserves were not as efficiently converted into grain yield as standard bread wheat cultivars, primarily due to the growth of tall, unproductive tillers, and lower kernel number and kernel size. There was no evidence of spelt yielding better than common wheat under conditions of P-deficiency. There is great potential to breed improved spelt genotypes through relatively simple modification of yield components and phenology, but whether this can be achieved while maintaining the grain quality attributes valued highly by the organic industry remains to be seen. Breeding for improved spelt should target reduced height and tiller number, early flowering, and larger kernels

Sustainable Grains Production Course - building grains industry futures

The Sustainable Grains Production course was established in 2003 by the University of New England (UNE) with funding from Grains Research and Development Corporation (GRDC). The aim of the course was to improve the knowledge and skills base of people, particularly advisors, working in the northern grains region of Australia, and to increase the economic and environmental performance of the grains industry. Through a survey of past and current students, UNE and GRDC sought to review the impact of the Sustainable Grains Production course on graduates, and within the grains industry. The survey was conducted in October, 2011, with 70 responses being received from 150 valid email addresses. Fifty percent of respondents were agronomists, and an additional 20% were from farms, with most from NW NSW and SE Queensland. Grains (GRNS) study was valued for its specificity in grains production, and the opportunity it gave students to develop their knowledge and skills in grain production in areas which were directly relevant to their careers. As a result of their study, 75% of respondents had spoken to farmers about a broader range of issues, and 66% had made or suggested changes to farming systems, showing that the course is achieving its intended outcomes of increasing grains industry human capacity, and accelerating the adoption of research findings. Additionally, all respondents thought that the grains industry benefitted from the course, and 57% of students thought that GRNS study had helped them obtain a promotion or new job