Water-use efficiency on irrigated dairy farms in northern Victoria and southern New South Wales

Abstract

A survey of 170 randomly selected, irrigated, dairy farms in northern Victoria and 9 in southern New South Wales was conducted to examine and benchmark the key factors influencing water-use efficiency. Water-use efficiency was defined as the amount of milk (kg milk fat plus protein) produced from pasture per megalitre of water (irrigation plus effective rainfall). Information on water-use, milk production, supplementary feeding, farm size and type, pasture management, and irrigation layout and management was collected for each farm by personal interview for the 1994–95 and 1995–96 seasons. The farms were ranked in the order of water-use efficiency with the average farm compared with the highest and lowest 10% of farms.

The range in water-use efficiency was 25–115 kg milk fat plus protein/ML, with the highest 10% averaging 94 kg/ML and the lowest 10% averaging 35 kg/ML. The large range in water-use efficiency indicated potential for substantial improvement on many farms. The high water-use efficiency farms, when compared with the low group: (i) produced a similar amount of milk from less water (387 v. 572 ML) (P<0.05), less land (48 v. 83 ha) (P< 0.05) and a similar number of cows (152 v. 143 cows); (ii) had higher estimated pasture consumption per hectare (11.5 v. 5.5 t DM/ha) (P<0.01) and per megalitre (1.0 v. 0.5 t DM/ML) (P<0.01); (iii) had higher stocking rates (3.2 v. 1.8 cows/ha) (P<0.01); (iv) used higher rates of nitrogen fertiliser (59 v. 18 kg N/ha.year) (P<0.05) and tended to use more phosphorus fertiliser (64 v. 34 kg P/ha.year) (P<0.10); (v) used similar levels of supplementary feed (872 v. 729 kg concentrates/cow); (vi) had higher milk production per cow (396 v. 277 kg fat plus protein) (P<0.05); and (vii) directed a higher proportion of the estimated energy consumed by cows into milk production (53 v. 46%) (P<0.05).

The survey data confirmed that irrigated dairy farm systems are complex and variable. For example, the amount of feed brought in from outside the milking area varied from 0 to 74% of the estimated total energy used by a milking herd. There was a large range in the level of supplement input amongst the farms in the high water-use efficiency group, and in the low water-use efficiency group. This indicates that the management of the farming system has a greater impact on the efficiency of water-use on irrigated dairy farms, than the type of system.

The data from the survey provide information for individual farms, a measure of the water-use efficiency of the industry, and an indication of the quality of regional land and water resources.