Assessing the Spatial Variability of Soil Properties to Delineate Nutrient Management Zones in Smallholder Maize-Based System of Nigeria

Table 3

Best-fitted semivariogram model parameters of soil variables of the study location.

Soil properties	Nugget	Sill	NSR	SDC	Range (km)	Model	RMSE	RMSSE	MPE
pH	0.003	0.010	0.31	Moderate	31.07	Exponential	0.50	1.2	0.01
Sand (%)	0.032	0.145	0.22	Strong	6.09	Exponential	14.90	1.2	0.12
Silt (%)	0.000	0.404	0.00	Strong	68.14	Stable	9.79	1.8	−0.47
Clay (%)	0.134	0.200	0.67	Moderate	2.14	Circular	8.05	0.9	−0.14
OC (%)	0.028	0.054	0.52	Moderate	34.87	Stable	0.23	1.1	0
TN (%)	0.027	0.846	0.03	Strong	8.26	Stable	0.02	1.4	0
Av.P (mg kg^−1)	0.146	0.941	0.16	Strong	17.51	Exponential	4.45	1.93	−0.04
K (cmol+ kg^−1)	0.058	0.241	0.24	Strong	12.92	Exponential	0.21	1.8	−0.01
ECEC (cmol+ kg^−1)	0.000	0.018	0.00	Strong	2.00	Stable	2.13	1.15	−0.07
EA	0.000	0.004	0.00	Strong	22.53	Stable	0.04	2.5	0
Ca (cmol+ kg^−1)	0.000	0.193	0.00	Strong	2.99	Stable	1.64	0.97	0.01
Mg (cmol+ kg^−1)	0.086	0.203	0.42	Moderate	11.01	Exponential	0.60	1.4	−0.03
Na (cmol+ kg^−1)	0.084	0.168	0.50	Moderate	28.30	Exponential	0.04	0.8	0
Cu (mg kg^−1)	0.133	0.404	0.33	Moderate	6.73	Circular	2.55	2.1	−0.14
Zn (mg kg^−1)	0.051	2.319	0.02	Strong	21.65	Stable	23.00	4.5	−0.92
Mn (mg kg^−1)	0.215	0.670	0.32	Strong	10.16	Exponential	63.40	3.2	2.05
Fe (mg kg^−1)	0.000	0.078	0.00	Strong	0.07	Stable	47.70	1.2	−0.61

OC: organic carbon, TN: total nitrogen, Av.P: available phosphorus, Ca: calcium, Mg: magnesium, Na: sodium, K: exchangeable potassium, ECEC: effective cation exchange capacity, Zn: zinc, Cu: copper, Mn: manganese, Fe: iron, EA: exchangeable acidity, NSR: nugget-to-sill ratio, SDC: spatial dependency class (strong <25%, moderate 25–75%, weak >75%), RMSE: root mean square error, RMSSE: root mean square standardised error, and MPE: mean prediction error.