Sustained growth response of Pinus radiata on podzolised sands to site management practices

Summary

Pinus radiata was planted at a second rotation site after three methods of site preparation: retention of logging residues, and clearing or broadcast burning of residues followed by cultivation. These were superimposed with weedicide and fertiliser treatments. Growth and nutrition of trees were monitored over 15 years.

Growth at age 5 years was significantly better where logging residues were retained rather than cleared or burned. A significant growth response was observed to weed control plus P applied at planting. Addition of N, K, Zn and other micronutrients at planting did not increase growth appreciably. Levels of N and P declined from 15 to 11 mg⁻¹ and from 1.5 to 1.1 mg⁻¹ respectively by age 8 years. Growth response to a second application of P at age 9 years was significantly better where logging residues were retained. However, levels of N in foliage remained low after this second application of P indicating a requirement for N as well as P fertiliser. Retention of logging residues improved tree growth on a sustained basis until age 15 years.

It is concluded that growth of P. radiata on a podzolised sandy soil is strongly influenced by residue management, weed control, and N and P nutrition. The results show that conservation of organic matter and nutrients by retaining logging residues is the best current practice for successive crops of pine growing on podzolised sandy soils in southern Australia.