Nutrient imbalances of smallholder dairy farming systems in Indonesia: The relevance of manure management

CONTEXT: Nitrogen (N) and phosphorus (P) imbalances from dairy farming systems (DFSs) lead to environmental problems, such as eutrophication. OBJECTIVE: This study aimed to quantify nutrient deficits and losses from DFSs with different manure management systems (MMSs) at the farm level and at the levels of its sub-systems. METHODS: We compared N[sbnd]P balances of 30 farms with four different MMSs: applying manure directly on forage land, without treatment (ADL), selling or exporting manure (SEL), using manure for anaerobic digestion (ADI), and discharging manure (DIS). N[sbnd]P balances were calculated based on differences between in- and outflows. RESULTS AND CONCLUSIONS: Results showed that N balances at DFS averaged 222 kg N farm⁻¹ yr⁻¹ and did not differ between MMSs. Average P balances at DFS differed between MMSs; balances were highest for DIS (83 kg P farm⁻¹ yr⁻¹), and lowest for SEL (−25 kg P farm⁻¹ yr⁻¹). Soil P balances did not differ between MMSs and were mostly negative, except for four ADL farms. Annually, all dairy farms in Lembang region are estimated to cause a nutrient loss of ∼1061 tons of N and ∼ 290 tons of P, and extract 8 tons of P from soils. Overall, high NP imbalances are caused by discharging manure into the environment. SIGNIFICANCE: To reduce imbalances, collection and on-farm use of manure must be improved, and excess manure needs to be sold to crop farms. The carrying capacity for high-input high-output dairy farming is determined by the capacity of arable farms to apply the manure surpluses.