Can low input dairy systems be economically and environmentally sustainable? Results from a farmlet study

A two-year dairy study was conducted under irrigation at Lincoln, Canterbury, comparing 1. Moderate stocking rate (MSR, 3.9 cows/ha; comparative stocking rate (CSR) of 89 kg live weight (LWT)/t DM (dry matter) offered; 150 kg nitrogen (N) fertiliser/ha/year; grain supplementation of 0.55 t DM/cow/year; wintering cows off- farm); or 2. Low stocking rate (LSR, 2.9 cows/ha; CSR of 91 kg LWT/t DM offered; grazing diverse pasture (Italian ryegrass, plantain, red- and white clover); 103 kg N fertiliser/ha/year; wintering cows on-farm). The Lincoln University Dairy Farm (LUDF; 3.4 cows/ha; CSR of 76 kg LWT/t DM offered; 169 kg N fertiliser/ha/year) was the benchmark. Milk yield, pasture production and quality data were modelled in FARMAX and OverseerFM to estimate financial and environmental performance of each farm. Performance was similar for MSR and LUDF. LSR gave the best environmental outcome across 2018/19 and 2019/20, leaching approximately 31% less N compared with MSR and LUDF. However, annual milk solids per ha were 28% less for LSR relative to MSR and LUDF. Correspondingly, the annual operating profit per ha was 35% less for LSR compared with LUDF. These financial losses can be mitigated in an LSR system if the farmer adopts more complex pasture management.