Modelling soil nitrogen mineralisation in semi-mature pine stands of South Africa to identify nutritional limitations and to predict potential responses to fertilisation

Table 5 Detailed data on the upper 15-cm layer of soil plus stand information required for the SNAP model per site. N mineralisation rate under laboratory conditions with temperature at 39 °C (sites A–H) and 30 °C (S1–L4) and soil water near field capacity

Site	Soil depth	Bulk density	WC at incubation	WC at field capacity	WC as % of FC	Litter depth	Litter mass	Fractional litter cover	Fractional weed cover	Fractional canopy cover	Basal N mineralisation	Normalised gross N availability estimate	Modelled Net annual N mineralisation
Site	(cm)	g cm⁻³	%	%	%	cm	t ha⁻¹	(0–1)	(0–1)	(0–1)	mg N (kg of topsoil)⁻¹ day⁻¹	mg N (kg of topsoil)⁻¹ day⁻¹	kg N (ha of topsoil)⁻¹ year⁻¹
A	0–15	1.4	15	20	71	6.9	4.4	0.95	0.30	0.50	1.53	2.89	180
B	0–15	1.4	19	19	100	16.0	14.8	0.95	0.80	0.49	0.27	1.72	27
C	0–15	1.1	18	26	71	19.1	12.3	0.95	0.70	0.88	0.67	2.12	43
D	0–15	1.3	20	25	78	16.2	7.7	0.95	0.90	0.69	0.49	1.95	37
E	0–15	1.1	18	25	72	21.1	8.1	0.90	0.80	0.73	0.86	2.16	55
F	0–15	1.1	18	25	70	12.7	7.9	0.95	0.90	0.69	0.63	2.01	36
G	0–15	1.0	21	25	83	21.5	8.7	0.95	0.70	0.95	1.62	2.68	65
H	0–15	1.1	21	26	80	20.3	14.0	0.95	0.90	0.76	0.48	1.61	27
S1	0–15	1.5	22	22	100	2.9	2.6	0.42	0.50	0.42	0.19	0.40	11
S2	0–15	1.6	25	25	100	6.8	8.3	0.79	0.05	0.79	1.50	1.93	93
S3	0–15	1.5	21	21	100	3.8	3.8	0.60	0.15	0.60	0.34	0.78	24
S4	0–15	1.5	24	24	100	8.2	10.3	0.93	0.10	0.93	0.22	0.81	14
L2	0–15	1.6	24	24	100	3.5	3.4	0.52	0.15	0.52	0.24	0.52	16
L4	0–15	1.4	39	39	100	8.8	11.2	0.95	0.05	0.95	0.93	1.22	54

ISSN: 1297-966X