
TY  - JOUR
A1  - Falkiner, RA 
A1  - Khanna, PK 
A1  - Raison, RJ 
T1  - Effect of superphosphate addition on N mineralization in some Australian forest soils
JF  - Soil Research
JO  - Soil Res.
Y1  - 1993
VL  - 31
IS  - 3
SP  - 285
EP  - 296
KW  - N-Mineralization;Phosphorus;Nitrification;
UR  - https://doi.org/10.1071/SR9930285 
N2  - Pinus radiata stands are reported to accumulate increased N on addition of phosphatic fertilizers. Field and laboratory studies were initiated to determine if addition of superphoshate increases soil N mineralization in forest soils. In a field experiment, application of 200 kg P ha-1 as superphosphate to trenched plots in a Pinus radiata stand increased accumulated soil mineral-N contents by 122% and 82% above the control on two occasions. Application of 500 kg P ha-1 as superphosphate either alone or in combination with lime (10 Mg ha-1) increased in situ soil net N mineralization in a dry sclerophyll eucalypt forest from 20.7 (control) to 28.3 (+P) and 30.2 (+P+lime) kg N ha-1 yr-1 20 cm-1. Uptake by the vegetation accounted for all of the mineralized nitrogen. In a 180 day laboratory incubation using undisturbed soil columns (0-20 cm) from nine forest sites, seven soils showed a positive response to superphosphate (100 kg P ha-1) addition, with increases in N mineralization ranging from 14% to 117%. The response of N mineralization to superphosphate addition was not related to initial soil organic C, total N or P content in the 0-20 cm layer. However, soil pH and organic C combined to account for 76% of the variation in N mineralization response (P < 0.01). In the 0-5 cm layer of untreated soils, soil organic P content could explain 71% of the variation in net N mineralization. Addition of superphosphate appears to increase N mineralization in several Australian forest soils and the improved availability of N will enhance tree growth rates. The mechanisms underlying the response are still poorly understood and thus also our ability to predict its significance for tree nutrition on specific forest sites. 
ER  -

