Abstract

The decoupling of dairy production from cropland can increase environmental burdens and constrain the recycling of nutrients in manure in land-limited, purchased-feed-dependent large-scaled dairy farms. This study evaluated the environmental and marginal economic effects of dairy–cropland recoupling using a cradle-to-farm-gate life cycle assessment and a 10,000-iteration Monte Carlo simulation. The observed farm system was used as the reference, and five partial forage-localization scenarios and one land-unconstrained full-localization benchmark were constructed by replacing off-farm domestic or imported forages with nutritionally equivalent farm-grown alternatives. Baseline global warming potential (GWP), nitrogen footprint (NFP), and phosphorus footprint (PFP) were 0.92 kg CO2e, 9.72 g N, and 0.43 g P per kg of fat- and protein-corrected milk, respectively. Replacing off-farm domestic alfalfa hay with farm-grown alfalfa hay provided the strongest combined environmental performance per unit of supporting cropland, reducing the GWP and NFP by 1.17 kg CO2e/m2 and 2.76 g N/m2, respectively, while also achieving the largest PFP reduction among the partial-localization scenarios. In contrast, replacing imported alfalfa hay generated the greatest marginal economic benefit (USD 0.37/m2) but increased the NFP by 0.12 g N/m2, revealing a clear environmental–economic trade-off. Full forage localization reduced system-level GWP by 12.0% but required approximately 3731 ha of supporting cropland, far exceeding the farm’s 133 ha site area. The environmental and marginal economic effects of recoupling depended on the displaced forage supply chain and on scenario-specific differences in transportation, manure nutrient recycling, fertilizer substitution, and crop-production inputs. These findings support the partial and priority-based allocation of supporting cropland as a practical strategy for large-scaled dairy farms with similar purchased-feed dependence and land constraints, rather than complete forage self-sufficiency.

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