Aspects of low fertiliser nitrogen input seasonal pasture-based milk production

Scully, Katie (2022) Aspects of low fertiliser nitrogen input seasonal pasture-based milk production. Doctoral thesis, SETU Waterford.

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Synthetic fertiliser nitrogen (N) is a significant contributor to the environmental footprints of dairy products from pasture-based systems. Biological N fixation (BNF) in association with white clover can reduce dependency on fertiliser N and consequently lower environmental footprints. This thesis investigated aspects of white clover management strategies in seasonal pasture-based dairy production. One experiment quantified the supply of background N in Irish permanent grasslands. Another investigated the productivity of white clover-based grassland for milk production based on several systems-scale studies. A third experiment examined the effect of fertiliser N input to grass-clover swards and calving date on the productivity of pasture-based dairy production. Mean background N was 141 kg ha-1 across Irish grasslands and varied both temporally and spatially during the growing season. The background N was influenced by soil physical and chemical properties along with meteorological factors. Dairy production based on low-input clover-based grassland receiving fertiliser N input of approximately 97 kg N ha-1 was similar to N-fertilised grass-only receiving 244 kg N ha-1 in several systems-scale studies. Mean annual and seasonal pasture production per ha and milk production per cow was similar between these two grassland systems. Sward white clover and BNF decreased with increasing annual N fertilisation. A mean calving date in mid-February is recommended for zero-fertiliser N input white clover-based systems. A later than typical calving date (in mid-April) resulted in inefficient use of pasture for milk production in a zero-fertiliser N white clover-based system. Extending lactation into the following winter resulted in lower concentrations of milk constituents and affected processing characteristics of late lactation milk. Nevertheless, maximising overwintering of stolon and root dry matter mass by tight winter grazing increased white clover productivity and persistence in grassland. There is considerable potential for milk production on clover-based swards receiving low or no input of fertiliser N.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Fertiliser nitrogen, Pasture-based milk production
Departments or Groups: *NONE OF THESE*
Divisions: School of Science > Department of Chemical and Life Sciences
Depositing User: Derek Langford
Date Deposited: 23 Feb 2023 12:05
Last Modified: 23 Feb 2023 12:05

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