Changes in topsoil, standing litter and tree nutrient content of a Pinus patula plantation after phosphorus and potassium fertilization

Abstract

A major goal for sustainable forestry management is to prevent a decline in soil fertility over time. The impact of phosphorus (P) and potassium (K) fertilization on the nutrients in the foliage, standing litter and topsoil (0 to -10 cm) at the end of the third crop rotation (at age 15 years) was determined. Three quantities (20/20, 40/40 and 80/80 kg ha -1 ) of both P and K fertilizer was applied at different stages of stand development (all at planting, all post-pruning at age 5 years, or applying 20/20 at planting and the rest post-pruning). The results showed that the effect of P fertilizer was more pronounced than the effect of K fertilizer. Compared to the control, the application of 80/80 PK fertilizer increased the concentration of plant available P (Bray II) in the first -10 cm of the topsoil from 3 to 12 mg P kg -1 and increased the foliar P level to 0.13%. The foliar P as well as the concentration of plant available P in the topsoil increased when the fertilizer was applied post-pruning. The split application of either 40/40 or 80/80 PK fertilizer increased the stemwood P concentration by 50%, compared to the 23 mg P kg -1 on the control plots. Application of the 40/40 and 80/80 quantities of fertilizer increased the dry mass (DM) of the standing litter layer by 27 Mg DM ha -1 (35%), which also affected the P and K content per hectare. A larger proportion of the applied fertilizer-K than fertilizer-P was removed from the site in stemwood and stembark, indicating that the re-application of K in the subsequent rotations will be important for sustainable production.

Critical Nutrient Concentrations and DRIS Norms for <em>Pinus patula</em>

“…reported by the same authors [1], P critical concentration coincided with the one determined in the 287 present study (0.13 %), confirming that such concentration corresponds to an adequate P status for P.…”

“…particularly when it is combined with management practices that decrease inter and intraspecific 25 competition for above and belowground resources [1]. Choice of the appropriate type of fertilizer, 26 dose, and application method require knowledge of the stand nutrient status, since each site has its 27 own soil and climate properties, and nutrient requirements vary among tree species [2,3].…”

The importance of harvest residue and fertiliser on productivity of Pinus patula across various sites in their first, second and third rotations, at Usutu Swaziland

“…The differential decomposition rates of foliage, branches, bark and nonutilisable timber explains the continued nutrient supply (Saarsalmi et al 2010). Other trials at Usutu have shown that the retention of organic matter plays an important role in the nutrient cycling of especially P (Crous et al 2007b(Crous et al , 2008(Crous et al , 2011a. Germishuizen (1979) reported that site C9 (Q-set) was more productive, than A9 (M-set) and D5 (Q/T-set) by 7 and 31% respectively in the F1R and by 18 and 44% in the F2R plot treatments with no fertiliser application respectively.…”

“…At Usutu, spot application of 20 kg ha − 1 of P and K fertiliser at planting and broadcast application of 75 kg ha − 1 of P and K fertiliser at first pruning at age 5 years, corrected the yield decline (Morris: Soil fertility and long term productivity of Pinus patula in the Usutu Forest Swaziland, Unpublished). Further research showed that a large proportion of P fertiliser was retained as residual P in the subsequent rotation as the inorganic P fertiliser was converted into organic P (P o ) forms (Crous et al 2007b(Crous et al , 2011a.…”

Conocimientos y prácticas ancestrales y tradicionales fortalecen la sustentabilidad de los sistemas hortícolas de la parroquia de San Joaquín

“…The lack of statistical differences, especially in the N-treatment, implies that all soils responded similarly to N additions ( Table 2), and that the differences in initial NH (Crous et al, 2011). In initial soil samples NH + 4 -N was the dominant form in all soils.…”