Improved nitrogen supply to cereals in Central Queensland following short legume leys

Abstract

Summary. The growth and ability of 12 summer-growing annual and perennial legumes to fix nitrogen and the response of a subsequent wheat crop was examined in a field trial on a deep cracking clay soil in the Central Highlands of Queensland. Twelve legumes [Lablab purpureus cv. Highworth, Vigna radiata cv. Satin, Macroptilium atropurpureum cv. Siratro, Medicago sativa cv. Trifecta, Vigna trilobata (CPI 13671), Macroptilium bracteatum (CPI 27404), Glycine latifolia (CQ 3368), Desmanthus virgatus cv. Marc, Desmanthus virgatus cv. Bayamo, Stylosanthes sp. aff scabra (104710), Clitoria ternatea cv. Milgarra, Cajanus cajan cv. Quest)] and grain sorghum (Sorghum bicolor cv. Tulloch) as a non-legume control were established in November 1994 and their growth monitored until March 1995. The legumes averaged greater than 5 t/ha dry matter production and 77 kg N/ha (above-ground only). Dry matter production ranged from less than 2 t/ha for G. latifolia and M. sativa to greater than 9 t/ha for D. virgatus cv. Bayamo and C. cajan. Annual legumes initially had much higher relative growth rates than the perennial legumes but they rapidily exhausted all the plant available water content of the soil thus allowing the well-established perennials to eventually match this production. The proportion of plant nitrogen (above ground) derived from N2 fixation was generally low, reflecting high soil NO3, but varied widely between species ranging from less than 20% for D. virgatus cv. Marc and G. latifolia to over 45% for C. ternatea, S. scabra and V. trilobata. The quantity of nitrogen derived from fixation was correlated with above-ground dry matter and nitrogen content. There was a significant (P<0.05) growth response by wheat following legumes compared with that following sorghum in the increasing order V. radiata = M. atropurpureum = L. purpureus > C. cajan = M. sativa = V. trilobata = M. bracteatum = G. latifolia > S. scabra = D. virgatus = C. ternatea. Previous legume growth had no significant (P>0.05) effect on yield or nitrogen concentration in a second ‘plant-back’ crop (sorghum). It was concluded that a wide range of pasture-ley legumes have the potential to improve cereal crop production in this region.

The yield and quality of fresh and ensiled plant material from intercropped maize (Zea mays) and beans (Phaseolus vulgaris)

“…In the experiments reported here the cereal and legume were in close contact, and this may be necessary for the cereal to benefit from nitrogen fixed by the legume. Some benefit may also be obtained in subsequent years by succeeding crops, 16 but this will depend on whether the nitrogen is leached from the root zone by rainfall before the next cropping season.…”

Agronomic Performance of Sorghum and Groundnut Cultivars in Sole and Intercrop Cultivation under Semiarid Conditions

“…It may also indicate greater agronomic advantages of intercropping under environmental stress conditions as a result of more efficient utilization of growth resources than in sole cropping. Cereal/legume intercropping could benefit farmers with small holdings by generating a sustainable income, minimizing the risk of crop failure, minimizing pest incidence and allowing better utilization of land resources (Armstrong et al. 1977, Aggarwal et al.…”

Poor adoption of ley-pastures in south-west Queensland: biophysical, economic and social constraints

“…In this context, Armstrong et al (1997) suggested that if the primary aim of the incorporation of ley-pastures into the crop rotations is to supply N for subsequent cereal crops, then one season of legume growth is enough, rather than perennial leypastures, where establishment, persistence and regeneration over several seasons are rarely perfect. They reported that better wheat growth was recorded in plots previously sown to lablab for just 4 months compared with continuous wheat.…”

“…They reported that better wheat growth was recorded in plots previously sown to lablab for just 4 months compared with continuous wheat. A greater N benefit is possible through annuals, as decomposition rates of plant material would be faster, whereas roots of perennials would be alive and less prone to decomposition (after Armstrong et al 1997). Armstrong et al (1999) further suggested that the poor growth of perennials during winter and spring was likely to limit the period over which they could support liveweight gain by stock, compared with fast-growing and high-yielding annual summer forages, such as lablab.…”