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Titolo:
EFFECTS OF GRAZING ON PLANT AND SOIL-NITROGEN RELATIONS OF PASTURE-CROP ROTATIONS
Autore:
UNKOVICH M; SANFORD P; PATE J; HYDER M;
Indirizzi:
UNIV WESTERN AUSTRALIA,DEPT BOT NEDLANDS WA 6907 AUSTRALIA UNIV WESTERN AUSTRALIA,CTR LEGUMES MEDITERRANEAN AGR NEDLANDS WA 6907AUSTRALIA WESTERN AUSTRALIA DEPT AGR,ALBANY REG OFF ALBANY WA 6330 AUSTRALIA
Titolo Testata:
Australian Journal of Agricultural Research
fascicolo: 3, volume: 49, anno: 1998,
pagine: 475 - 485
SICI:
0004-9409(1998)49:3<475:EOGOPA>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOUTH-WEST AUSTRALIA; NATURAL-ABUNDANCE TECHNIQUE; SUBTERRANEAN CLOVER; N-2 FIXATION; ACID SOILS; MINERAL-N; REDUCTION; PRECISION; NITRATE; LEGUMES;
Keywords:
NITROGEN FIXATION; GRAZING INTENSITY; SUBTERRANEAN CLOVER; NITRATE; AMMONIUM; GRAIN PROTEIN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
M. Unkovich et al., "EFFECTS OF GRAZING ON PLANT AND SOIL-NITROGEN RELATIONS OF PASTURE-CROP ROTATIONS", Australian Journal of Agricultural Research, 49(3), 1998, pp. 475-485

Abstract

Plant and soil nitrogen (N) fluxes were assessed in subterranean clover (Trifolium subterraneum L.) based pastures set-stocked at 8 sheep per hectare (light grazing) or grazed at a much higher, but variable, intensity to maintain 1400 kg standing dry matter per hectare (intensive grazing) through the addition or removal of sheep. Pasture composition and biomass production, herbage N concentration, plant nitrate (NO3-) utilisation, and N-2 fixation by clover were assessed at 3-weekly intervals over the growing season. Soil ammonium (NH4+) and NO3- availability were assessed at similar intervals using soil coring and in situ incubation cores. Seasonal pasture yield under light grazing was 11.5 t dry matter/ha compared with 7.9 t/ha under intensive grazing, the difference being mostly attributable to reduced grass growth under intensive grazing. However, there was essentially no difference between the pastures in total N accumulation (300 kg N/ha in the lightly grazedand 302 kg N/ha in the intensively grazed pastures). The lesser dry matter production under intensive grazing was compensated for by higherN concentration and increased clover content of the sward, and fasterclover growth late in the growing season. Nz fixation by clover underintensive grazing (153 kg N/ha) was slightly greater than under lightgrazing (131 kg N/ha). Proportional dependence of clover on N-2 fixation (%Ndfa) was similar under intensive grazing (78%) and light grazing (84%), despite higher continued availability of soil mineral N underintensive grazing. Uptake of soil N by the grass component amounted to 147 kg N/ha under light grazing v. 96 kg N/ha in the intensively grazed pasture, and for the clover was 18 and 40 kg N/ha, respectively. Capeweed (Arctotheca calendula L.), a common weed of south-west Australian pastures, was extraordinarily active in absorbing, storing, and reducing soil NO3-, especially when subjected to intensive grazing. After the 3 years of the grazing trial, the pastures were cultivated and cropped to oats, triticale, and canola and the biomass and N uptake of each crop assessed. Intensive grazing in the previous pasture resultedin increased availability of soil mineral N in the subsequent cropping phase and accordingly augmented crop N uptake and eventual grain protein levels relative to crops following lightly graced pasture. The study indicated that intensive grazing before cropping may offer a useful management tool for improving N nutrition and yields of non-leguminous crops in pasture-crop rotations under the conditions prevailing in the south-west of Australia.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 27/09/20 alle ore 00:59:31