Early response of second rotation Pinus Patula to nitrogen and phosphate fertilizer at Sao hill and Shume forest plantations Tanzania
Maliondo, S.M.S|Chamshama, S.AO|Nsolomo, V.R|Mhando, M.L / 2000

Forest stand fertilisation is considered to be one of the options for increasing the productivity of second rotation stands of fast growing tropical pine plantations. A fertiliser trial was initiated at one site in Shume Forest Project (NE Tanzania), and at two sites in Sao Hill Forest Project (SW Tanzania), to examine the effect of Nitrogen (N) and Phosphate (P) fertilisers on the growth of 2-year old Pinus patula. All sites were in the second rotation of the same species. Seedlings were planted in April 1997 at Shume, and in March 1998 at Sao Hill. . Treatments consisted of two rates of N (0, 60 kg N ha-1) and three of P (0, 30, 60 kg P ha-1) in a randomised complete block design replicated thrice. The six factorial treatments were applied in April 1998 at Shume, and April 1999 at Sao Hill. At Shume, tree heights were measured in May 1997 and May 1998; both height and diameter at breast height (DBH) in September 1998, and October 1999. Foliage samples were collected in March 1999 and analysed for N, P, K, Ca and Mg concentrations (%) and contents (mg/fascicle weight). At the Sao Hill sites tree heights were measured in November 1998 and 1999, respectively.Application of P at Shume significantly (P<0.05) depressed DBH from 1.68± 0.10 in the control to 1.45 ±0.14 cm in the fertilised plots, but had no significant effect on height. Measurements taken at Sao Hill in November 1998 (6 months before fertilisation), showed that tree height at the two sites in Sao Hill differed significantly ((P<0.001), with trees at Ngwazi significantly taller (45.35±2.59cm) than at Msiwasi (36.39±4.13cm). However, these differences were no longer significant six months after fertilisation. Application of N increased stem height and height increment, but the effect was non-significant. Application of P fertiliser increased height and one-year height increment at both sites in Sao Hill, but this was only significant (P<0.05) at Msiwasi. Mean heights were 132.2±21.0cm in the control, 144.4±21.4cm at 30 kg P ha-1, 158.7±6.2cm at 60 kg P ha-1. Height increments were 94.8±19.4, 107.7±23.6, and 123.6±7.6cm. Foliar K concentration (%) was depressed by addition of P fertiliser (P<0.05) from 1.88 ± 0.44% in the control to 1.31± 0.06% at the highest P rate at Shume. Foliar N content was increased by P fertilisation from 1.48±0.23 (mg per fascicle weight) in the control to 1.87± 0.50 at the highest P rate.Above results, although preliminary, indicate that fertilisation with N and P may not be justified at Shume since there was no positive response two years after fertilisation. Results from Sao Hill strongly indicate a positive response to P within the first year at one site, but not in the other. This emphasises the need for developing site-specific fertiliser recommendations based on research studies.