Farm Table says:
What is the problem?
A Lucerne pasture requires a recovery period of a defoliation event and that recovery time is more important than the level of defoliation.
Repeated defoliation with inadequate recovery leads to loss of production and reduced stand life. Early recommendations were for Lucerne to be grazed or cut in fixed rotations with a fixed recovery period throughout the year – typically 5-7 weeks. Current recommendations favor grazing when new lucerne shoots reach 2 cm and grazing for 7-8 days leaving shoots at least 5 cm long. They also often recommend resting lucerne in late summer-autumn until approximately 50% flowering to allow root reserves to be restored prior to winter.Field experiments were conducted to measure the effects of defoliation/recovery treatments on root and shoot DM, root C and N reserves and persistence of Lucerne.
What did the research involve?
The field experiments were conducted in Hamilton and Rutherglen to measure the effects of 4 defoliation/recovery treatments. This paper examines the effect of several defoliation regimes, representing those recommended in the past or present, on the maintenance of root yield during the first 5 months of treatment.
What were the key findings?
To date, there are no differences in basal frequency of Lucerne between treatments at either site. Root mass has changed between treatments at Hamilton but a consistent pattern has not yet emerged. Root mass has increased at Rutherglen despite poor above ground herbage production. This is surprising considering the generally dry summer-autumn period during the study to date and considering that the Short Rotation treatment has a recovery period considerably shorter than that generally recommended.
The different defoliation treatments have had little effect on root carbon reserves to date. This is surprising considering the generally dry summer-autumn period during the study to date, and considering that the SR treatment has a recovery period considerably shorter than that generally recommended.