To investigate the effect of two different methods of surface drainage ('raised beds' and 'hump and hollows') of pasture compared to an undrained control treatment on farm productivity and the potential impact on the environment. 

During 2006 and 2007, a field trial designed to quantify the effect of two different surface drainage strategies of pasture (hump & hollow and raised beds) on farm productivity, profitability and sustainability was conducted on a commercial farm near Derrinallum. Under the rainfall conditions experienced for the two years of the trial, it is concluded that the use of raised beds for the growing of pastures for grazing has little to offer the sheep industry. On the basis of the data obtained in this trial, it is recommended that the hump & hollow system is the preferred method of surface drainage for sheep grazing systems in this environment and should be promoted in the region. Major findings included:

• In both years, total annual pasture dry matter (DM) yields from the raised bed treatment were substantially less than for the undrained and the hump & hollow treatments.
• In the drought year of 2006 the raised bed treatment grew 37% (2.8 t DM/ha) less while the hump & hollow treatment grew only 7% (0.6 t DM/ha) less than the undrained (total of 7.6 t DM/ha).
• In the higher rainfall 2007 year the raised bed treatment produced 15% (1.6 t DM/ha) less pasture than the undrained. In contrast, the hump & hollow grew 10% (1.1 t DM/ha) more than the undrained (total of 10.7 t DM/ha) in 2007.
• The reasons for the lower than expected pasture yields on the raised beds are speculated to be a combination of low yields in the furrows, poorer plant establishment and density on the beds, and a reduction in the water holding capacity of the soil relative to the other treatments.
• Soil physical health was however considerably better on the raised beds than the other treatments. Aeration porosities at field capacity in November 2007 were a very healthy 16.3% in the raised beds, a moderate 11.8% for the hump & hollow and a poor 7.0% for the undrained.
• No significant differences in ewe or lamb weights at weaning were found between treatments in either year. This was most likely due to the set stocked sheep having pasture on offer in excess of requirements for most of the spring. In 2006 however, the raised beds were stocked at around 1 ewe/ha less due to the lower pasture growth rates.
• From a catchment and general environmental health perspective, the water run‐off results raise some concerns about the environmental impact of growing and grazing pastures on raised beds.
• The raised beds proved to be very effective in removing excess water from the pasture. Over 2007, the raised bed treatment (47.1 mm) had 170% more runoff water than the undrained (17.4 mm) while the hump & hollow (26.7 mm) had 53% more runoff.
• Both drainage treatments had considerably higher concentrations of, and total loads of phosphorus (P) and nitrogen (N) in runoff water. Of particular concern were the losses of 0.5 and 0.4 kg P/ha for the raised bed and hump & hollow treatments respectively compared to 0.1 kg P/ha for the undrained in 2007. For N, corresponding losses were 6.3, 2.1 and 0.9 kg N/ha for the raised beds, hump & hollow and undrained respectively.
• It is recommended that if raised beds are to be used for grazed pastures, then the best practice recommendations developed for raised bed cropping also be applied to pasture.