Aiming to produce the biggest bucket of milk from every bucket of water, James Neal and colleagues at Camden are achieving dry matter yields up to 31 tonnes per hectare. The sprinklers are computer controlled to water 32 different trial forages to perfection.

Where dairy forages are adequately watered, fertilised and appropriately managed, dry matter yields up to 31 tonnes per hectare are achievable - more than four times what the average NSW farmer produces. Research at the University of Sydney at Camden is also showing that no particular forage is suitable for growing throughout the whole year.

Perennial ryegrass has been the dominant forage used on Australian dairy farms.

'However its poor persistence has become an issue under current farm management, and many farmers are seeking alternatives,' says NSW DPI research agronomist James Neal.

'Water availability is likely to decrease as cost increases through competition from other agricultural pursuits, demands for environment flows and metropolitan areas,' he said.

'So the dairy industry's priority must be to maximise profitability by producing the biggest bucket of milk from every bucket of water.'

In a large field-based evaluation of 32 forages backed by Dairy Australia and NSW DPI, each species is being evaluated for its dry matter yields (DMY), water use efficiency (WUE) and nutrient characteristics. WUE is the ratio of the DMY to the water used from rainfall, irrigation and the soil profile.

Under adequate irrigation and fertiliser, the highest DMY for a 12 month period was achieved by maize of 31 tonnes of dry matter per hectare (t/DM/ha).

'Not only did maize produce four times the DMY of perennial ryegrass and white clover during the summer, the WUE of the maize was also three times higher,' DrNeal said.

Over the summer, maize used five megalitres (ML) of water to produce 29t DM/ha, while perennial ryegrass used 3.2ML to produce only 6.5t DM/ha.

Of the other species, the four perennial grasses - perennial ryegrass, prairie grass, fescue and kikuyu - had the highest DMY of around 27-28t DM/ha for a 12 month period.

However, their seasonal production was markedly different. Under adequate irrigation, perennial ryegrass produced more dry matter and had the highest WUE in winter. During summer the reverse was true; kikuyu and fescue produced more dry matter and had a higher WUE than perennial ryegrass or prairie grass.

Besides irrigating to maximise dry matter production, two other irrigation treatments investigated how the different forages responded to increasing water stress.

The adequate water supply was reduced by 66 per cent or 33pc toinduce stress.

The seasonal response differed significantly between species.

The loss in yield in summer to the most extreme water stress treatment ranged from 33pc for lucerne to 82pc for white clover.

While there was substantial effect on DMY, the effect of water stress on WUE depended on the species.

Even at the highest water deficit, there was no effect on WUE for maize, kikuyu and paspalum.

However, WUE was substantially reduced in white clover fescue and perennial ryegrass.

This research highlights the importance of selecting species suited to seasonal conditions to maximise the conversion of water to milk.

Contact: James Neal, Camden, (02) 4655 0713.

This story appears in Agriculture Today.