Limiting grazing periods combined with proper housing can reduce nutrient losses from dairy systems

Abstract

Pasture-based and grass-fed branding are often associated with consumer perceptions of improved human health, environmental performance and animal welfare. Here, to examine the impacts of dairy production in detail, we contrasted global observational (n = 156) data for nitrogen and phosphorus losses from land by the duration of outdoor livestock grazing in confined, grazed and hybrid systems. Observational nitrogen losses for confined systems were lowest on a productivity—but not area—basis. No differences were noted for phosphorus losses between the systems. Modelling of the three dairy systems in New Zealand, the United States and the Netherlands yielded similar results. We found insufficient evidence that grazed dairy systems have lower nutrient losses than confined ones, but trade-offs exist between systems at farm scale. The use of a hybrid system may allow for uniform distribution of stored excreta, controlled dietary intake, high productivity and mitigation of animal welfare issues arising from climatic extremes.

Balancing nitrogen at the farm gate

“…Current pastoral dairy systems in Uruguay have lower stocking rates and productivity than pasture-based dairy systems from New Zealand, Australia, Northern Europe, or the US (c.f. Table 1 vs. McDowell and others (29) ; Luo & Ledgard (30) ; Ros and others (31) ). Likewise, the N surplus of current Uruguayan dairy systems, at 71 kg N ha -1 , is at the lower end of the values reported for pastoral dairy systems worldwide (9) , less than half the national average dairy N surplus of New Zealand (30) (186-281 kg N ha -1 ), Australia (32) (156 kg N ha -1 ), Ireland (33) (155 kg N ha -1 ), or the Netherlands (34) (174-208kg N ha -1 ).…”

Fate of fertiliser nitrogen in a ryegrass–kikuyu dairy pasture system

“…(2016) of 223 and 124 kg N ha −1 , respectively. In several countries and dairy systems (New Zealand, grazing; Denmark, grazing and housed; United States, housed), farm-gate N surplus and N losses were modelled in the ranges 177–306 and 30–65 kg N ha −1 year −1 , respectively (McDowell et al . 2022).…”

“…The values of N surplus (86-325 kg N ha −1 ) and N lost (22-142 kg N ha −1 ) in Experiment 2 are in agreement with findings by Rowlings et al (2016) of 223 and 124 kg N ha −1 , respectively. In several countries and dairy systems (New Zealand, grazing; Denmark, grazing and housed; United States, housed), farm-gate N surplus and N losses were modelled in the ranges 177-306 and 30-65 kg N ha −1 year −1 , respectively (McDowell et al 2022). In Australia, the N surplus and N losses in a modelled study and farmlet study were 156-352 and 78-237 kg N ha −1 year −1 (Eckard et al 2007;Christie et al 2018).…”

Phosphorus applications adjusted to optimal crop yields can help sustain global phosphorus reserves

“…There is also pressure on phosphorus to be conserved by increasing our intake of plant-based foods instead of using phosphorus to feed crops for livestock that are then used to feed people-wasting some phosphorus in unutilized fodder or animal products 36 . Additional pressure via policy to improve water quality make it unlikely that deficits in improved grasslands for intensive land uses such as dairying will be alleviated 37 . Our conclusion from these data and trends is that through adjusting phosphorus fertilizer application rates, we can achieve optimal yields without increasing the rate at which phosphorus reserves are being depleted.…”