Aggregate breakdown mechanisms as affected by soil texture and organic matter in soils dominated by primary minerals

Figures & data

Figure 1 Soil sampling sites (source: Nciizah and Wakindiki 2012)

Table 1 Selected soil physical, chemical and mineralogical properties for the 14 ecotopes. EC = electrical conductivity, POM = particulate organic matter, SOM = soil organic matter

Ecotope	Usea	Texture (%)			EC (µS m^-1)	Textural classb	Climatec	pH	SOM (g kg^-1)	POM(%)	Mineralogyd
		Sand	Clay	Silt							H	K	Q	S
Alice Jozini	C	60	12	28	47.90	SL	SA	5.78	35.7	20.25	0.29	–	77.01	–
Amatola Jozini	C	47	37	15	28.47	SCL	SH	5.80	66.1	18.08	1.91	32.4	28.88	14.7
Debenek	C	56	18	26	49.23	SL	SA	5.79	24.0	39.58	0.30	2.1	–	–
Kamastone	C	72	19	9	66.47	SL	SA	6.27	31.8	28.62	0.67	8.6	5.96	–
Lujiko Leeufontein	C	68	19	11	52.23	SL	SA	5.45	38.2	20.05	0.63	–	75.14	–
Mamatha	C	61	18	21	34.50	SL	SA	5.50	29.9	24.82	0.43	–	75.32	–
Mbems Koedosvlei	P	56	21	23	55.17	SCL	SA	5.65	34.3	28.48	1.10	–	77.35	–
Mbems Koedosvlei	C	56	22	22	80.97	SCL	SA	5.76	42.7	32.74	0.65	–	76.37	–
Ncera Kinross	C	48	26	26	61.50	SCL	SH	5.08	41.9	16.52	1.12	9.3	61.90	9.9
Newtondale	C	65	21	14	40.34	SCL	SA	6.25	51.4	29.38	0.76	–	72.74	–
Ngwenya Jozini	C	72	18	10	41.27	SL	SA	6.49	36.4	27.45	0.56	–	68.22	–
Ngwenya Swartland	P	67	21	12	53.57	SCL	SA	5.53	28.4	35.42	0.66	–	68.11	–
Phandulwazi Jozini	P	58	21	21	37.80	SCL	SA	5.49	24.7	34.49	0.58	–	86.85	–
Pirie Shorrocks	C	50	22	28	45.89	L	SH	5.33	44.1	19.37	0.55	–	68.55	–

a C = cultivation, P = pasture

b L = loam, SC = sandy clay, SCL = sandy clay loam, SL = sandy loam

c SA = semi-arid, SH = subhumid

d H = hematite, K = kaolinite, Q = quartz, S = smectite (Nciizah and Wakindiki 2012)

Table 2 Aggregate stability expressed as mean weight diameter and coefficient of vulnerability (KV). FW = fast wetting, SW = slow wetting, WSt = wet stirring, P = pasture

Ecotope	Mean weight diameter (mm)				Coefficient of vulnerability
	FW	SW	WSt	Mean	KV1	KV2	KV3
Alice Jozini	0.36^g	0.44^i	0.42^f	0.41	10.06^a	8.18^a	8.30^a
Amatola Jozini	0.63^f	1.21^g	1.55^c	1.13	5.87^bc	2.92^bcd	2.28^e
Debenek	1.73^b	2.84^b	1.82^b	2.13	2.03^fg	1.23^fg	1.93^f
Kamastone	0.69^f	1.56e^f	0.84^e	1.03	5.0g^cd	2.25^cdef	4.15^c
Lujiko	2.73^a	3.23^a	2.64^a	2.87	1.28^g	1.08^g	1.33^g
Mamatha	0.98^e	2.02^d	1.59^c	1.53	3.74^de	1.73^efg	2.20^e
Mbems Koedosvlei	1.04^de	1.62^e	1.57^c	1.41	3.36^ef	2.18^cdef	2.23^e
Mbems Koedosvlei P	1.04^de	1.62^e	1.57^c	1.41	3.37^ef	2.18^cdef	2.23^e
Ncera Kinross	0.50^fg	1.176^g	1.32^d	1.00	7.13^b	3.06^bc	2.66^d
Newtondale	1.18^de	1.78^de	1.57^c	1.51	3.00^ef	1.97^defg	2.24^e
Ngwenya Jozini	0.52^fg	0.89^h	0.53^f	0.65	6.80^b	3.98^b	6.60^b
Ngwenya Swartland	1.23^d	2.31^c	1.40^d	1.65	2.86^ef	1.53^fg	2.50^d
Phandulwazi	1.47^c	2.84^b	1.82^b	2.03	2.39^efg	1.23^fg	1.93^f
Pirie Shorrocks	0.67^f	1.32^fg	1.32^d	1.10	5.23^c	2.68^cde	2.66^d
P-value	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05

Figure 2 Relationships between percentage particulate organic matter (POM) and mean weight diameter (MWD)

Nciizah AD, Wakindiki IIC. 2012. Particulate organic matter, soil texture and mineralogy relations in some Eastern Cape ecotopes in South Africa. South African Journal of Plant and Soil 29: 39–46.

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