caa a22 4500 477112013 CHVBK 20180405111611.0 cr unu---uuuuu 170330e19960501xx s 000 0 eng 10.1007/BF00011001 doi (NATIONALLICENCE)springer-10.1007/BF00011001 Application of 15N and xylem ureide methods for assessing N2 fixation of three shrub legumes periodically pruned for forage [Elektronische Daten] [Mark Peoples, Brian Palmer, Dianne Lilley, Lam Duc, David Herridge] The apparently diminished capacity for N2 fixation by the shrub legume Calliandra calothyrsus (Calliandra) relative to other woody perennial legumes was investigated in a field experiment in northern Queensland, Australia. In this trial, (i) the proportion of plant nitrogen (N) derived from symbiotic N2 fixation (%Pfix) and the amounts of N2 fixed were compared in Calliandra, Gliricidia sepium (Gliricidia) and Codariocalyx gyroides (Codariocalyx), (ii) variations in N2 fixation due to season or tree age were determined, (iii) estimates of Pfix derived with the 15N natural abundance technique were compared with values obtained from 15N enrichment or xylem sap ureide procedures to determine whether the previous conclusions about Calliandra's ability to fix N had resulted from specific problems with the natural abundance methodology used in the earlier studies. Inoculated seedlings of each of the three shrub legume species were planted in dense stands (1.5 m rows, 0.5 m between trees) in two randomised blocks. The northern block was used solely for natural abundance measurements, while 15N-enriched KNO3 (10 atom % 15N excess) was applied four times over a 52 week period to plots in the southern block. The non-nodulating tree legume Senna spectabilis (formally Cassia spectabilis) was used as a non-N2-fixing reference for the 15N-based procedures, with Guinea grass (Panicum maximum) included as an additional non-fixing check. Growth by the trees above 75 cm was first cut and removed after 22 weeks and regrowth was subsequently pruned periodically for another 95 weeks. Sampling for dry matter production, N yield and estimates of Pfix were restricted to the central four of the 32 plants which constituted each replicate plot. Information generated during the 117 week study indicated that estimates of Pfix by 15N natural abundance were closely similar to values derived with 15N-enrichment or sap ureides. The data indicated that Calliandra had a reduced reliance upon N2 fixation relative to Gliricidia and Codariocalyx for the first 65 weeks after establishment. This appeared to be due to more prolifc root growth by Calliandra than either of the other N2-fixing species and an ability to extract a greater proportion of its N requirements from soil mineral N. However, after week 65 and for the remainder of the experiment, estimates of Pfix for Calliandra were similar to the other shrub legumes. Over 117 weeks, prunings from Calliandra and Gliricidia had removed 52-58 t dry matter ha-1, and between 1471 and 1678 kg N ha-1, of which 1026-1063 kg N ha-1 was estimated to have been derived from N2 fixation. At the time of final harvest, 65-73% of the fixed N was present in shoot regrowth of the N2 fixing shrubs, 9-18% in the roots, 15% in the trunk, and 2-6% in fallen leaves. Kluwer Academic Publishers, 1996 Calliandra calothyrsus nationallicence Codariocalyx gyroides nationallicence Gliricidia sepium nationallicence 15N enrichment nationallicence 15N natural abundance nationallicence ureides nationallicence Peoples Mark CSIRO Division of Plant Industry, GPO Box 1600, 2601, Canberra, ACT, Australia aut Palmer Brian CSIRO Division of Tropical Crops and Pastures, Davies Laboratory, PMB PO Aitkenvale, 4814, Queensland, Australia aut Lilley Dianne CSIRO Division of Plant Industry, GPO Box 1600, 2601, Canberra, ACT, Australia aut Duc Lam Center of Nuclear Techniques, HoChiMinh City, Vietnam aut Herridge David NSW Agriculture, RMB 944, 2340, Tamworth, NSW, Australia aut Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl 182/1(1996-05-01), 125-137 0032-079X 182:1<125 1996 182 11104 https://doi.org/10.1007/BF00011001 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00011001 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Peoples Mark CSIRO Division of Plant Industry, GPO Box 1600, 2601, Canberra, ACT, Australia aut NATIONALLICENCE 700 1- Palmer Brian CSIRO Division of Tropical Crops and Pastures, Davies Laboratory, PMB PO Aitkenvale, 4814, Queensland, Australia aut NATIONALLICENCE 700 1- Lilley Dianne CSIRO Division of Plant Industry, GPO Box 1600, 2601, Canberra, ACT, Australia aut NATIONALLICENCE 700 1- Duc Lam Center of Nuclear Techniques, HoChiMinh City, Vietnam aut NATIONALLICENCE 700 1- Herridge David NSW Agriculture, RMB 944, 2340, Tamworth, NSW, Australia aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl/ 182/1(1996-05-01), 125-137 0032-079X 182:1<125 1996 182 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer