| Abstrakt: |
Pinus taeda plantations in subtropical regions of South America commonly occur on highly weathered soils of low natural fertility, especially phosphorus (P). Thus, phosphate fertilization is necessary in Pinus. The proposition of critical levels (CL) and sufficiency ranges (SR) of P in needles and soil can assist forest managers to decide the use of phosphate fertilizers, reducing the cost of production and the potential for contamination. The study aimed to propose critical levels and sufficiency ranges of phosphorus in young Pinus taeda submitted to phosphate fertilization in southern Brazil. The parameters height, stem diameter, P concentration in needles, soil available P, electron transport rate (ETRm), maximum potential quantum yield of PSII (Fv/Fm), initial (Fo) and maximum fluorescence (Fm), chlorophyll a (Chl a), b (Chl b) and total (Chl total) concentration, and acid phosphatase (APase) activity were evaluated. Productivity factor, CL and SR of P in needles and soil were calculated. The CL of P in needles in relation to relative productivity factor was 1.5 g P kg− 1. The CL of P for photosynthetic parameters were 1.5 and 1.7 g P kg− 1 for Chl b and ETRm, respectively. CL of P in soil was 2.3 mg P dm− 3. The results may contribute to appropriate recommendations for phosphate fertilizer, reducing production costs and possible P–fertilizer losses in Pinus taeda plantations. [ABSTRACT FROM AUTHOR] |
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