Predicting fertilizer response in established loblolly pine plantations with basal area and site index.

Estimates of b.a./acre, number of stems/acre, mean d.b.h., 5-yr gross volume increment/acre and 5-yr mortality volume/acre were calculated for plots from 44 fertilizer trials established in the North Carolina Coastal Plain and Piedmont. Gross and net volume increment equations were developed using b.a., site index, and fertilizer treatment as predictor variables. Response to fertilization was calculated as the difference between growth estimates for control and fertilized stands at given b.a. and site index. Predicted 5-yr volume responses from fertilization with 100 lb/acre N and 50 lb/acre P are tabulated for a range of b.a. and site index, and were found to be related to stand conditions. (Refs. 8).