A 6-YEAR COMPARISON OF NITRATE LEACHING FROM GRASS CLOVER AND N-FERTILIZED GRASS PASTURES GRAZED BY SHEEP/

Citation
Sp. Cuttle et al., A 6-YEAR COMPARISON OF NITRATE LEACHING FROM GRASS CLOVER AND N-FERTILIZED GRASS PASTURES GRAZED BY SHEEP/, Journal of Agricultural Science, 131, 1998, pp. 39-50
Citations number
49
Categorie Soggetti
Agriculture,"Agriculture Dairy & AnumalScience
ISSN journal
00218596
Volume
131
Year of publication
1998
Part
1
Pages
39 - 50
Database
ISI
SICI code
0021-8596(1998)131:<39:A6CONL>2.0.ZU;2-U
Abstract
Nitrate leaching was measured over a 3-year period from rotationally g razed perennial ryegrass (Lolium perenne L.) pasture receiving 200 kg fertilizer-N/ha and from similarly grazed ryegrass/white clover (Trifo lium repens L.) pasture that received no N fertilizer. The results are discussed together with those from the same plots in the preceding 3 years when they were stocked continuously. Under both managements, the numbers of grazing sheep were adjusted on the basis of the quantity o f herbage available on the plots. During the whole 6 years, mean nitra te concentrations in soil water collected by porous cup samplers remai ned below the European Union limit of 11.3 mg N/1 except for the ferti lized grass plots in year 5 of the study. Quantities of nitrate leache d ranged from 6 to 34 kg/ha per year from the grass/clover plots and 2 -46 kg/ha from the fertilized plots. Leaching losses from both types o f pasture were positively correlated with the numbers of lamb grazing days in the later part of the grazing season. This relationship and th e high spatial variability associated with the measurements indicated that N derived from excreta was the main source of leached nitrate. It was concluded that, where pastures of equal productivity are compared , similar quantities of N are likely to be leached from grass/clover s wards as from grass swards receiving N fertilizer.