CONTEXT

Global dairy production contributes a relatively large share of the total emissions of nitrogen (N) and phosphorus (P) to air and water bodies, which are a concern. However, there are large differences among dairy farming systems in performance, and these differences are not well understood. This relates especially to emerging market economies such as China, where dairy production is increasing, and where new dairy farms are relatively large, intensive, and on small areas of farmland.

OBJECTIVES

This study estimated the N and P flows and use efficiencies (NUE and PUE) of 141 dairy farms at the farm, herd, and manure management levels. Emission mitigation technologies were also explored to identify the effects of improving farm nutrient use efficiencies on each farm via scenario analyses.

METHODS

We collected data from farm surveys and feed sample analyses. Based on the empirical management data, a nutrient flow model was developed and used for the quantification of nutrient flows.

RESULTS AND CONCLUSIONS

We found substantial variation among the farms in NUE (53 ± 20%) and PUE (84 ± 22%) at the farm level, but not at the herd level. Our estimates of NUE and PUE were much higher, and N and P losses were much lower, than previous estimates. The effects of management technologies varied greatly among farms; increases in farm-level NUE ranged from 0 to 53% and in PUE from 0 to 79%. Improving manure storage and treatment technologies and increasing manure export had relatively large effects on farm-level NUE and PUE and nutrient losses, while the effects of low-protein feeding were limited.

SIGNIFICANCE

Our findings highlight the need for farm-specific technologies targeted to specific aspects of the whole manure management chain to improve the NUE and PUE of the industrial dairy production sector in China. Furthermore, manure application limits are needed to prevent excessive manure applications and nutrient losses from croplands.