Pasture

While the primary focus for liming has been to increase crop yields, the fact that liming also boosts pasture growth and sheep production should not be overlooked. Local research has shown liming increases clover and medic growth leading to higher yields in following crops (Devenish, AgWA & Lightfoot, Aglime of Australia). However, there is little local information about the effect of liming on pasture composition and sheep production. NSW Agriculture (and cooperating organisations) established a long term liming trial in 1992 at Book Book, NSW (Helyar et al, 1994, 1997). Results have shown liming significantly improves a range of parameters including pasture composition and sheep liveweight gain. In 1992, the limed plots received 3.7 t/ha of lime. This was incorporated to 10cm with a disc harrow increasing the pH from 4.1 to 5.5 in this layer. One aim of the trial was to maintain the top 10cm around pH 5.5 enabling some lime to leach into the subsoils and treat acidity to depth. In the study reported here, both annual and perennial pasture treatments under permanent pasture and pasture/cropping rotations were measured.

Pasture Responses

The main effect of liming was to increase feed quality in this trial. The botanical composition at peak yield in October 1996 and 1997 shows liming increased the proportion of high quality species (phalaris, ryegrass and subclover in perennial pastures and ryegrass and subclover in annual pastures) and reduced the proportion of less desirable grass and broadleaf weeds.

Animal Responses

In 1993, the stocking rates were the same on all treatments. Sheep liveweight gains were significantly greater where lime was applied to either annual or perennial pastures. Subsequently, stocking rates on the unlimed treatments were reduced to 75% of the limed treatment in an attempt equalise liveweight gains. During 1994 sheep growth rates were still higher on the limed treatment possibly reflecting the carryover feed from 1993. This was a relatively important factor as 1994 was a drought in NSW. In the winter of 1995 and autumn of 1996 sheep growth rates were lower on the limed treatments (which had 25% higher stocking rates). In the winter of 1996, the stocking rate of the limed treatments was reduced so it was only 10% rather than 25% higher than the unlimed treatment. The sheep liveweights on the limed treatments rapidly caught up to the unlimed treatment during that winter. In 1997, the stocking rates were returned to unlimed being 75% of the limed treatment.

Analysis of the stocking rates used over the 4 years shows that the carrying capacity of the limed treatment was about 3.5 DSE/ha greater than the unlimed treatment for all rotations (Figure 1).

The liveweight gain per hectare on the limed treatment was higher than that on the unlimed treatment. Higher stocking rates with lime increased wool production per hectare by 10-29% averaging 25% over 5 seasons (Figure 2). However, there was little difference between perennial and annual pastures in wool production.

References

• Helyar, KR; Conyers, MK and Cullis BR, 1994, Managing Acid Soils Through Efficient Rotations. Final Report to Australian Wool Research and Promotion Organisation , 1991-1994

• Helyar, KR; Conyers, MK, Cullis BR and Li GD, 1997, Managing Acid Soils Through Efficient Rotations. Final Report to IWS (International Wool Secretariat), 1994-1997

Acknowledgements

• Australian Wool Research Promotion Organisation / IWS 1991-1997. MRC/IWS/LWRRDC, 1994-1997. GRDC, 1997-2002

• Omya Southern Pty Ltd, Incitec Pty Ltd

• Research Team from NSW Agriculture: Helyar, KR; Conyers, MK; Li, GD; Cullis BR; Risher, RP; Poile, G and Castleman, LJ

• Cooperating Researchers: Cregan, PD, Charles Sturt University Wagga Wagga