Effects of cultivation method on the early growth of Pinus radiata on a low-quality site in north-eastern Tasmania
Survival and growth of Pinus radiata on a low-quality texture-contrast soil in north-eastern Tasmania were compared over a five-year period following five different cultivation treatments: no cultivation, ripping, mounding, ripping + mounding or spot cultivation. Soil penetration resistance after two years, and root abundance after 4.5 years, were also measured. After five years, there were no significant differences in survival between treatments. Ripping + mounding produced the best height growth after five years, followed by mounding, ripping, spot cultivation and lastly no cultivation. However, only mounding and ripping + mounding produced significantly greater height growth compared to no cultivation. Comparisons of plot mean basal area (m2) and volume per hectare (m3 ha-1) showed trends similar to mean height after five years, with ripping + mounding producing the highest basal area and volume. However, only the differences between ripping + mounding and no cultivation were significant. Soil penetration resistance, measured after two years, was significantly lower at depths <45 cm following either ripping + mounding or spot cultivation compared to no cultivation. Root abundance after 4.5 years was significantly higher following ripping + mounding compared to the other four treatments. Growth was therefore consistently superior following ripping + mounding when compared to the other treatments, although the results indicate that any type of cultivation is preferable to no cultivation at all. On highly erodible soils, such as those at the trial site, spot cultivation might be preferable to continuous cultivation (ripping and/or mounding) in order to minimise the risk of erosion and subsequent pollution of waterways by suspended sediments.