Effects of fertilization on growth of eight-year-old Caribbean pine in West Guangdong

Objective In order to study the fertilizer response in an eight-year-old Pinus caribaea var.caribaea plantation in Yangjiang to the application of different proportions of nitrogen(N), phosphorus(P) and potassium(K) fertilizers mixed with microelements.

Method There were 17 top application treatments of different proportions of N, P and K fertilizers mixed with microelements.The growth and foliar nutrient concentrations of P.caribaea var.caribaea were determined after 15 months.

Result The covariance analysis showed that the optimum proportion of fertilizers was N (21.5 g·plant^-1) and P₂O₅ (30 g·plant^-1).The individual stem volume of plants fertilized with 50 g urea+250 g calcium magnesium phosphate fertilizer+25 g KCl for 15 months was increased by 23.6% on average compared to the blank control.The treatments with P (N₂P₁K₂, N₂P₂K₂) had significantly more growth compared to the P deficiency treatment (N₂P₀K₂).In addition, boron(B) application significantly increased the stem volume under the same N, P and K treatment.

Conclusion P and B are both important for P.caribaea var.caribaea growth after canopy closure.The proportion of N and P plays an essential role in regulating the fertilizer response of P.caribaea var.caribaea.