Research Report No. 351

Response of radiata pine to fertilizer and chemical weed control at Neerim East.  P. Hopmans and I. B. Tomkins.  April 1992.  14pp. (unpubl.)

SUMMARY

A trial having a factorial design with 3 replications of 3 levels of superphosphate (nil, 180 g tree-1, 700 kg ha-1) and 4 levels of Velpar L herbicide (nil, spot, broadcast granular and broadcast liquid) was set up in 1979 to examine effects of phosphate fertiliser and chemical weed control on survival and early growth of Pinus radiata D. Don (radiata pine) at Neerim East in Victoria.

Survival at 3 years after planting was generally less than desirable (69% to 84%) particularly for unfertilised trees with weed control. Low survival in this study was attributed primarily to browsing by animals.

Application of phosphate fertiliser at planting is essential for good establishment and satisfactory early growth of radiata pine on these phosphorus deficient sites at Neerim East. Spot and broadcast applications of superphosphate without weed control increased basal area ten-fold at age 10 years. However, foliar phosphorus declined to deficient levels indicating the need for a second application of fertiliser at age 5 years for the spot fertiliser and at age 10 years for the broadcast fertiliser treatments. The combination of spot or broadcast fertiliser plus complete weed control at planting increased basal area at age 10 years nearly twenty-fold.

Results of this study show that foliar phosphorus levels are maintained at satisfactory levels for longer with a broadcast application of fertiliser at planting compared with a spot application. However, spot application requires less fertiliser (295 kg ha-1 vs 700 kg ha-1) and gives the same or slightly better growth response up to age 5 years. It is therefore recommended that new plantings of radiata pine at Neerim East should be treated with superphosphate at 180 g tree-1 followed by chemical weed control soon after planting. Foliar analysis indicates that this should be followed up with a second application of phosphate fertiliser at age 5 years.