We are hearing from researchers of late that the current rates of lime application (common industry practice is 2.5 t/ha every 10 years) are not addressing the current soil acidification rate and that an effective liming program should aim to increase soil pH (CaCl2) to 5.5 in the top 10 cm, not 5.0 as has been the current practice.
This will provide sufficient lime to raise pH in the surface soil and allow for excess lime to leach into deeper acidic subsoil layers and slowly increase pH at depth.
We know that top-dressed lime moves very slowly into the subsoil layers, about 1 cm/year, depending on soil type, rainfall and lime application rate. Incorporation of the lime after spreading is recommended to 'speed up' the reaction of lime with the soil to greater depth. This might be achievable in flat, cropping paddocks further west but what about sloping, rocky, pasture paddocks commonly found in the NSW southern slopes? What liming strategy should landholders adopt if they cannot or choose not to incorporate lime after spreading?
Holbrook Landcare Network, in conjunction with NSW DPI, will attempt to answer these questions through two newly established lime demonstration sites supported by the Australian Government's Smartfarms program, on properties near Holbrook and Tumbarumba. The sites will investigate the optimal rates and frequency of top-dressed lime on established pastures - high rate up front or more frequent lower rates? And the influence on subsoil, pasture production, composition, and persistence.
These sites are additional to our lime trial sites at Burrumbuttock and Morven that are currently in a cropping phase and are testing different lime rates, with and without incorporation. In the long-term, we aim to attract funding to monitor pH change under the different lime rates and measure pasture response to the various treatments.
