Vector analysis identify loblolly pine (Pinus taeda L.) phosphorus deficiency on a Beauregard soil

Bekele, A.; Hudnall, W.H.; Tiarks, A.E.

General Technical Report Southern Research Station, USDA Forest Service ( SRS-30): 474-479


Accession: 003609735

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The response of densely stocked one-year-old loblolly pine (Pinus taeda) to N and P fertilizers on a Beauregard silt loam (fine silty, siliceous, thermic, Plinthaquic Paleudults) was studied in Kisatchie National Forest, Louisiana. A "continuous function" experimental design with three replications was used. Each replication consisted of 12 mx12 m plots, with three trees planted within a square metre area for each treatment. Ten levels each of N and P were applied. Application rates ranged from: 0 to 240 kg N/ha (as urea), and 0 to 900 kg P/ha (as triple superphosphate). Potassium was applied at a uniform rate of 50 kg/ha (as muriate of potash). Phosphorus and K application rates were based upon adsorption isotherms, while N application rates were based upon a previous study on the same soil. Vector analysis provides an opportunity for simultaneous comparison of plant growth, nutrient concentration and nutrient content on one graph. Vector analysis revealed that P application increased P concentration, P content and dry weight, showing that unfertilized trees were deficient in P. Nitrogen-only application had an antagonistic effect on P by reducing P concentration, P content and dry weight. Enhanced growth was observed when both N and P were applied in combinations.