Nitrogen fixation in fababeans as affected by plant population density in sole or intercropped systems with barley

Growth and N2fixation in mixed cropping ofMedicago arboreaandAtriplex halimusgrown on a salt-affected soil using a15N tracer technique

“…In this study, it was observed that the inclusion of saltbush in the mixed cropping system severely decreased soil and fertilizer N uptake by shrubby medic and enhanced %N 2 fixation. It was previously observed that %Ndfa of the legume increased due to an N-sparing effect (N concentration in legume rhizosphere is reduced) by the non-legume (Danso et al 1987). A similar observation was also reported by a recent study (Fan et al 2006).…”

“…Similarly, Kurdali et al (1996) reported that barley-vetch mixed stand significantly out-yielded plants in monoculture under rain fed conditions. On the other hand, the reduced dry matter and N yield of the shrubby medic and saltbush grown as mixed plants compared to solely grown plants in our study is a common observation in multiple cropping systems (Danso et al 1987;Tobita et al 1994;Kurdali et al 2003;Kurdali 2009). This indicates that the component crops compete with each other for the limited resources under the (Tobita et al 1994).…”

“…Increased N 2 fixation in the intercrop medic mainly resulted in a more efficient depletion of N from soil and fertilizer by the saltbush compared with that absorbed by the associated legume as previously reported by Hardarson et al (1988) for alfalfa-ryegrass swards, Izaurralde et al (1992) for the pea-barley intercrop, Kurdali et al (1996) for the vetch-barley mixed cropping, and Kurdali et al (1990) for the alder-poplar associations. High soil N content has been demonstrated to reduce N 2 fixation, with no adverse effect on yield (Danso et al 1987). Thus, N 2 fixation is capable of substituting for N from soil and fertilizer or vice versa.…”

“…This suggestion, however, merits further investigation to demonstrate the relationship between N 2 fixation and mycorrhizal fungi in this type of mixed cropping system. Danso et al (1987) reported that greater N 2 fixation may be achieved by the two forms, i.e. increase in the actual amount of N 2 fixed or the proportion fixed.…”

Nitrogen and sulphur management: challenges for organic sources in temperate agricultural systems

“…Long-term studies in the field have produced results of a similar order of magnitude for older pasture plants (Soussana & Hartwig 1996;Høgh-Jensen & Schjoerring 2001), as well as for some grain legumes (Sawatsky & Soper 1991;Jensen 1996c), with substantial uptake by companion non-legume crop species (Jensen 1996a). The significance of transfer of fixed N under field conditions within a season, for temperate inter-cropping systems, has yet to be clearly defined; reports from the limited data available are mixed (Danso et al 1987;Papastylianou 1988;Cowell et al 1989;Izaurralde et al 1992;Waterer et al 1994;Jensen 1996b). Overall, the amount of transfer will, of course, depend on plant species and plant age, as well as on the abiotic and biotic environment (Fujita et al 1992).…”